Table of Contents

New and Changed Information

Preface

Routing Overview

IP

Configuring IPv6

Configuring IP Services

Configuring WCCPv2

Configuring IPv4

Routing

Configuring OSPFv3

Configuring EIGRP

Configuring IS-IS

Configuring Basic BGP

Configuring Advanced BGP

Configuring RIP

Configuring Static Routing

Configuring Layer 3 Virtualization

Managing the Unicast RIB and FIB

Configuring Route Policy Manager

Configuring Policy Based Routing

Configuring OSPFv2

First-Hop Redundancy Protocols

Configuring HSRP

Configuring VRRP

Configuring Object Tracking

Configuring GLBP

RFCs

Configuration Limits

Glossary

Title

New and Changed Information

This chapter provides release-specific information for each new and changed feature in the Cisco Nexus 7000 Series NX-OS Unicast Routing Configuration Guide, Release 5.x. The latest version of this document is available at the following Cisco website:

http://www.cisco.com/en/US/docs/switches/datacenter/sw/5_x/nx-os/unicast/configuration/guide/l3_nxos-book.htm

To check for additional information about Cisco NX-OS Release 5.x, see the Cisco NX-OS Release Notes available at the following Cisco website:

http://www.cisco.com/en/US/partner/products/ps9402/prod_release_notes_list.html

Table 1 summarizes the new and changed features for the Cisco Nexus 7000 Series NX-OS Unicast Routing Configuration Guide, Release 5.x, and tells you where they are documented.

Table 1 New and Changed Features for Release 5.x

Feature

Description

Changed in Release

Where Documented

Policy-based routing and WCCPv2

Added support for policy-based routing and WCCPv2 on the same interface if bank chaining is disabled.

5.2(4)

Chapter 5, “Configuring WCCPv2” and Chapter 17, “Configuring Policy-Based Routing”

BFD on VRRP

Added BFD support to VRRP.

5.2(1)

Chapter 20, “Configuring VRRP”

BGP

Added support for the BGP PIC core feature.

5.2(1)

Chapter 10, “Configuring Basic BGP”

EIGRP

Added support for EIGRP wide metrics.

5.2(1)

Chapter 8, “Configuring EIGRP”

Maximum routes

Added support to configure the maximum number of routes allowed in the routing table.

5.2(1)

Chapter 15, “Managing the Unicast RIB and FIB”

Route-map enhancements

Added support for set extcommunity cost and set extcommunity rt commands.

5.2(1)

Chapter 16, “Configuring Route Policy Manager”

Route-policy enhancements

Added support for set interface commands.

5.2(1)

Chapter 17, “Configuring Policy-Based Routing”

VPN address mode

Added support for VPNv4 and VPNv6 address modes.

5.2(1)

Chapter 10, “Configuring Basic BGP”

IP Glean Throttling

Added support for glean throttling rate limiters to protect the supervisor from the glean traffic.

5.1(1)

Chapter 2, “Configuring IPv4”

WCCP

Added support for WCCPv2 Error Handling for SPM Operations.

5.1(1)

Chapter 5, “Configuring WCCPv2”

Static routing

Added the name option to the ip route command.

5.1(1)

Chapter 13, “Configuring Static Routing”

Layer 3 Interoperation with the N7K-F132-15 Module

Added support for the Layer 3 Interoperation with the N7K-F132-15 Module.

5.1(1)

Chapter 13, “Configuring Static Routing”

BFD

Added support for BFD.

5.0(2)

See the Cisco Nexus 7000 Series NX-OS Interfaces Configuration Guide, Release 5.x, for more information.

Dynamic TCAM allocation

Enabled by default and cannot be disabled.

5.0(2)

Chapter 15, “Managing the Unicast RIB and FIB”

IPv6

Added support for IPv6 Path MTU discovery

5.0(2)

Chapter 3, “Configuring IPv6”

HSRP

Added support for IPv6.

5.0(2)

Chapter 19, “Configuring HSRP”

Object Tracking

Added support for IPv6.

5.0(2)

Chapter 21, “Configuring Object Tracking”

IS-IS

Added support for BFD and stateful restart.

5.0(2)

Chapter 9, “Configuring IS-IS”

TCAM and FIB Size

Added support for larger TCAM and FIB sizes with XL modules.

5.0(2)

Chapter 15, “Managing the Unicast RIB and FIB”

Route Maps

Added support for match mac-list, match metric, and match vlan commands.

5.0(2)

Chapter 16, “Configuring Route Policy Manager”

Preface

This preface describes the audience, organization, and conventions of the Cisco Nexus 7000 Series NX-OS Unicast Routing Configuration Guide, Release 5.x. It also provides information on how to obtain related information.

This preface includes the following sections:

- Audience

- Organization

- Document Conventions

- Related Documentation

- Obtain Documentation and Submit a Service Request

Audience

To use this guide, you must be familiar with IP and routing technology.

Organization

This document is organized into the following chapters:

Title

Description

Chapter 1, “Overview”

Presents an overview of unicast routing and brief descriptions of each feature.

Chapter 2, “Configuring IPv4”

Describes how to configure and manage IPv4, including ARP and ICMP.

Chapter 3, “Configuring IPv6”

Describes how to configure and manage IPv6, including the Neighbor Discovery Protocol and ICMPv6.

Chapter 4, “Configuring DNS”

Describes how to configure DHCP and DNS clients.

Chapter 5, “Configuring WCCPv2”

Describes how to configure WCCPv2.

Chapter 6, “Configuring OSPFv2”

Describes how to configure the OSPFv2 routing protocol for IPv4 networks.

Chapter 7, “Configuring OSPFv3”

Describes how to configure the OSPFv3 routing protocol for IPv6 networks.

Chapter 8, “Configuring EIGRP”

Describes how to configure the Cisco EIGRP routing protocol for IPv4 networks.

Chapter 9, “Configuring IS-IS”

Describes how to configure the IS-IS routing protocol for IPv4 and IPv6 networks.

Chapter 10, “Configuring Basic BGP”

Describes how to configure basic features for the BGP routing protocol for IPv4 and IPv6 networks.

Chapter 11, “Configuring Advanced BGP”

Describes how to configure advanced features for the BGP routing protocol for IPv4 and IPv6 networks, including route redistribution and route aggregation.

Chapter 12, “Configuring RIP”

Describes how to configure the RIP for IPv4 networks.

Chapter 13, “Configuring Static Routing”

Describes how to configure static routing for IPv4 and IPv6 networks.

Chapter 14, “Configuring Layer 3 Virtualization”

Describes how to configure Layer 3 virtualization.

Chapter 15, “Managing the Unicast RIB and FIB”

Describes how to view and modify the unicast RIB and FIB.

Chapter 16, “Configuring Route Policy Manager”

Describes how to configure the Route Policy Manager, including IP prefix lists and route maps for filtering and redistribution.

Chapter 17, “Configuring Policy-Based Routing”

Describes how to configure route maps for policy based routing.

Chapter 18, “Configuring GLBP”

Describes how to configure GLBP.

Chapter 19, “Configuring HSRP”

Describes how to configure the Hot Standby Routing Protocol.

Chapter 20, “Configuring VRRP”

Describes how to configure the Virtual Router Redundancy Protocol.

Chapter 21, “Configuring Object Tracking”

Describes how to configure object tracking.

Appendix A, “IETF RFCs supported by Cisco NX-OS Unicast Features, Release 5.x”

Lists IETF RFCs supported by Cisco NX-OS.

Appendix B, “Configuration Limits for Cisco NX-OS Layer 3 Unicast Features”

Lists configuration limits for Cisco Nexus 7000 series devices.

Document Conventions

Command descriptions use these conventions:

Convention

Description

boldface font

Commands and keywords are in boldface.

italic font

Arguments for which you supply values are in italics.

[ ]

Elements in square brackets are optional.

[ x | y | z ]

Optional alternative keywords are grouped in brackets and separated by vertical bars.

string

A nonquoted set of characters. Do not use quotation marks around the string or the string will include the quotation marks.

Screen examples use these conventions:

screen font

Terminal sessions and information that the switch displays are in screen font.

boldface screen font

Information that you must enter is in boldface screen font.

italic screen font

Arguments for which you supply values are in italic screen font.

< >

Nonprinting characters, such as passwords, are in angle brackets.

[ ]

Default responses to system prompts are in square brackets.

!, #

An exclamation point (!) or a pound sign (#) at the beginning of a line of code indicates a comment line.

This document uses the following conventions:

Note Means reader take note. Notes contain helpful suggestions or references to material not covered in the manual.

Caution Means reader be careful. In this situation, you might do something that could result in equipment damage or loss of data.

Related Documentation

Cisco NX-OS includes the following documents:

Release Notes

Cisco Nexus 7000 Series NX-OS Release Notes, Release 5.x

NX-OS Configuration Guides

Cisco Nexus 7000 Series NX-OS Configuration Examples, Release 5.x

Configuring the Cisco Nexus 2000 Series Fabric Extender

Cisco Nexus 7000 Series NX-OS FabricPath Configuration Guide

Configuring Feature Set for FabricPath

Cisco NX-OS FCoE Configuration Guide for Cisco Nexus 7000 and Cisco MDS 9500

Cisco Nexus 7000 Series NX-OS Fundamentals Configuration Guide, Release 5.x

Cisco Nexus 7000 Series NX-OS High Availability and Redundancy Guide, Release 5.x

Cisco Nexus 7000 Series NX-OS Interfaces Configuration Guide, Release 5.x

Cisco Nexus 7000 Series NX-OS IP SLAs Configuration Guide

Cisco Nexus 7000 Series NX-OS Layer 2 Switching Configuration Guide, Release 5.x

Cisco Nexus 7000 Series NX-OS LISP Configuration Guide

Cisco Nexus 7000 Series NX-OS MPLS Configuration Guide

Cisco Nexus 7000 Series NX-OS Multicast Routing Configuration Guide, Release 5.x

Cisco Nexus 7000 Series NX-OS OTV Configuration Guide

Cisco Nexus 7000 Series OTV Quick Start Guide

Cisco Nexus 7000 Series NX-OS Quality of Service Configuration Guide, Release 5.x

Cisco Nexus 7000 Series NX-OS SAN Switching Configuration Guide

Cisco Nexus 7000 Series NX-OS Security Configuration Guide, Release 5.x

Cisco Nexus 7000 Series NX-OS System Management Configuration Guide, Release 5.x

Cisco Nexus 7000 Series NX-OS Unicast Routing Configuration Guide, Release 5.x

Cisco Nexus 7000 Series NX-OS Virtual Device Context Configuration Guide, Release 5.x

Cisco Nexus 7000 Series NX-OS Virtual Device Context Quick Start, Release 5.x

NX-OS Command References

Cisco Nexus 7000 Series NX-OS Command Reference Master Index

Cisco Nexus 7000 Series NX-OS FabricPath Command Reference

Cisco NX-OS FCoE Command Reference for Cisco Nexus 7000 and Cisco MDS 9500

Cisco Nexus 7000 Series NX-OS Fundamentals Command Reference

Cisco Nexus 7000 Series NX-OS High Availability Command Reference

Cisco Nexus 7000 Series NX-OS Interfaces Command Reference

Cisco Nexus 7000 Series NX-OS Layer 2 Switching Command Reference

Cisco Nexus 7000 Series NX-OS LISP Command Reference

Cisco Nexus 7000 Series NX-OS MPLS Command Reference

Cisco Nexus 7000 Series NX-OS Multicast Routing Command Reference

Cisco Nexus 7000 Series NX-OS OTV Command Reference

Cisco Nexus 7000 Series NX-OS Quality of Service Command Reference

Cisco Nexus 7000 Series NX-OS SAN Switching Command Reference

Cisco Nexus 7000 Series NX-OS Security Command Reference

Cisco Nexus 7000 Series NX-OS System Management Command Reference

Cisco Nexus 7000 Series NX-OS Unicast Routing Command Reference

Cisco Nexus 7000 Series NX-OS Virtual Device Context Command Reference

Other Software Documents

Cisco NX-OS Licensing Guide

Cisco Nexus 7000 Series NX-OS MIB Quick Reference

Cisco Nexus 7000 Series NX-OS Software Upgrade and Downgrade Guide, Release 5.x

Cisco NX-OS System Messages Reference

Cisco Nexus 7000 Series NX-OS Troubleshooting Guide

Obtain Documentation and Submit a Service Request

For information on obtaining documentation, using the Cisco Bug Search Tool (BST), submitting a service request, and gathering additional information, see What’s New in Cisco Product Documentation.

To receive new and revised Cisco technical content directly to your desktop, you can subscribe to the What’s New in Cisco Product Documentation RSS feed. The RSS feeds are a free service.

Overview

This chapter introduces the underlying concepts for the Layer 3 unicast routing protocols in Cisco NX-OS.

This chapter includes the following sections:

- Information About Layer 3 Unicast Routing

- Routing Algorithms

- Layer 3 Virtualization

- Cisco NX-OS Fowarding Architecture

- Layer 3 Interoperation with the N7K-F132-15 Module

- Summary of Layer 3 Unicast Routing Features

- Related Topics

Information About Layer 3 Unicast Routing

Layer 3 unicast routing involves two basic activities: determining optimal routing paths and packet switching. You can use routing algorithms to calculate the optimal path from the router to a destination. This calculation depends on the algorithm selected, route metrics, and other considerations such as load balancing and alternate path discovery.

This section includes the following topics:

- Routing Fundamentals

- Packet Switching

- Routing Metrics

- Router IDs

- Autonomous Systems

- Convergence

- Load Balancing and Equal Cost Multipath

- Route Redistribution

- Administrative Distance

- Stub Routing

Routing Fundamentals

Routing protocols use a metric to evaluate the best path to the destination. A metric is a standard of measurement, such as a path bandwidth, that routing algorithms use to determine the optimal path to a destination. To aid path determination, routing algorithms initialize and maintain routing tables that contain route information such as the IP destination address, the address of the next router, or the next hop. Destination and next-hop associations tell a router that an IP destination can be reached optimally by sending the packet to a particular router that represents the next hop on the way to the final destination. When a router receives an incoming packet, it checks the destination address and attempts to associate this address with the next hop. See the “Unicast RIB” section for more information about the route table.

Routing tables can contain other information, such as the data about the desirability of a path. Routers compare metrics to determine optimal routes, and these metrics differ depending on the design of the routing algorithm used. See the “Routing Metrics” section.

Routers communicate with one another and maintain their routing tables by transmitting a variety of messages. The routing update message is one such message that consists of all or a portion of a routing table. By analyzing routing updates from all other routers, a router can build a detailed picture of the network topology. A link-state advertisement, which is another example of a message sent between routers, informs other routers of the link state of the sending router. You can also use link information to enable routers to determine optimal routes to network destinations. For more information, see the “Routing Algorithms” section.

Packet Switching

In packet switching, a host determines that it must send a packet to another host. Having acquired a router address by some means, the source host sends a packet that is addressed specifically to the router physical (Media Access Control [MAC]-layer) address but with the IP (network layer) address of the destination host.

The router examines the destination IP address and tries to find the IP address in the routing table. If the router does not know how to forward the packet, it typically drops the packet. If the router knows how to forward the packet, it changes the destination MAC address to the MAC address of the next-hop router and transmits the packet.

The next hop might be the ultimate destination host or another router that executes the same switching decision process. As the packet moves through the internetwork, its physical address changes, but its protocol address remains constant (see Figure 1-1).

Figure 1-1 Packet Header Updates Through a Network

Routing Metrics

Routing algorithms use many different metrics to determine the best route. Sophisticated routing algorithms can base route selection on multiple metrics.

This section includes the following metrics:

- Path Length

- Reliability

- Routing Delay

- Bandwidth

- Load

- Communication Cost

Path Length

The path length is the most common routing metric. Some routing protocols allow you to assign arbitrary costs to each network link. In this case, the path length is the sum of the costs associated with each link traversed. Other routing protocols define the hop count, which is a metric that specifies the number of passes through internetworking products, such as routers, that a packet must take from a source to a destination.

Reliability

The reliability, in the context of routing algorithms, is the dependability (in terms of the bit-error rate) of each network link. Some network links might go down more often than others. After a network fails, certain network links might be repaired more easily or more quickly than other links. The reliability factors that you can take into account when assigning the reliability rating are arbitrary numeric values that you usually assign to network links.

Routing Delay

The routing delay is the length of time required to move a packet from a source to a destination through the internetwork. The delay depends on many factors, including the bandwidth of intermediate network links, the port queues at each router along the way, the network congestion on all intermediate network links, and the physical distance that the packet must travel. Because the routing delay is a combination of several important variables, it is a common and useful metric.

Bandwidth

The bandwidth is the available traffic capacity of a link. For example, a 10-Gigabit Ethernet link is preferable to a 1-Gigabit Ethernet link. Although the bandwidth is the maximum attainable throughput on a link, routes through links with greater bandwidth do not necessarily provide better routes than routes through slower links. For example, if a faster link is busier, the actual time required to send a packet to the destination could be greater.

Load

The load is the degree to which a network resource, such as a router, is busy. You can calculate the load in a variety of ways, including CPU usage and packets processed per second. Monitoring these parameters on a continual basis can be resource intensive.

Communication Cost

The communication cost is a measure of the operating cost to route over a link. The communication cost is another important metric, especially if you do not care about performance as much as operating expenditures. For example, the line delay for a private line might be longer than a public line, but you can send packets over your private line rather than through the public lines that cost money for usage time.

Router IDs

Each routing process has an associated router ID. You can configure the router ID to any interface in the system. If you do not configure the router ID, Cisco NX-OS selects the router ID based on the following criteria:

- Cisco NX-OS prefers loopback0 over any other interface. If loopback0 does not exist, then Cisco NX-OS prefers the first loopback interface over any other interface type.

- If you have not configured a loopback interface, Cisco NX-OS uses the first interface in the configuration file as the router ID. If you configure any loopback interface after Cisco NX-OS selects the router ID, the loopback interface becomes the router ID. If the loopback interface is not loopback0 and you configure loopback0 with an IP address, the router ID changes to the IP address of loopback0.

- If the interface that the router ID is based on changes, that new IP address becomes the router ID. If any other interface changes its IP address, there is no router ID change.

Autonomous Systems

An autonomous system (AS) is a network controlled by a single technical administration entity. Autonomous systems divide global external networks into individual routing domains, where local routing policies are applied. This organization simplifies routing domain administration and simplifies consistent policy configuration.

Each autonomous system can support multiple interior routing protocols that dynamically exchange routing information through route redistribution. The Regional Internet Registries assign a unique number to each public autonomous system that directly connects to the Internet. This autonomous system number (AS number) identifies both the routing process and the autonomous system.

Cisco NX-OS supports 4-byte AS numbers. Table 1-1 lists the AS number ranges.

Table 1-1 AS Numbers

2-Byte Numbers

4-Byte Numbers in AS.dot Notation

4-Byte Numbers in plaintext Notation

Purpose

1 to 64511

N/A

1 to 64511

Public AS (assigned by RIR)1

64512 to 65534

N/A

64512 to 65534

Private AS (assigned by local administrator)

65535

N/A

65535

Reserved

N/A

1.0 to 65535.65535

65536 to 4294967295

Public AS (assigned by RIR)

1.RIR=Regional Internet Registries

Note RFC 5396 is partially supported. The asplain and asdot notations are supported, but the asdot+ notation is not.

Private autonomous system numbers are used for internal routing domains but must be translated by the router for traffic that is routed out to the Internet. You should not configure routing protocols to advertise private autonomous system numbers to external networks. By default, Cisco NX-OS does not remove private autonomous system numbers from routing updates.

Note The autonomous system number assignment for public and private networks is governed by the Internet Assigned Number Authority (IANA). For information about autonomous system numbers, including the reserved number assignment, or to apply to register an autonomous system number, see this URL:

http://www.iana.org/

Convergence

A key aspect to measure for any routing algorithm is how much time a router takes to react to network topology changes. When a part of the network changes for any reason, such as a link failure, the routing information in different routers might not match. Some routers will have updated information about the changed topology, while other routers will still have the old information. The convergence is the amount of time before all routers in the network have updated, matching routing information. The convergence time varies depending on the routing algorithm. Fast convergence minimizes the chance of lost packets caused by inaccurate routing information.

Load Balancing and Equal Cost Multipath

Routing protocols can use load balancing or equal cost multipath (ECMP) to share traffic across multiple paths.When a router learns multiple routes to a specific network, it installs the route with the lowest administrative distance in the routing table. If the router receives and installs multiple paths with the same administrative distance and cost to a destination, load balancing can occur. Load balancing distributes the traffic across all the paths, sharing the load. The number of paths used is limited by the number of entries that the routing protocol puts in the routing table. Cisco NX-OS supports up to 16 paths to a destination.

The Enhanced Interior Gateway Routing Protocol (EIGRP) also supports unequal cost load balancing. For more information, see Chapter8, “Configuring EIGRP”

Route Redistribution

If you have multiple routing protocols configured in your network, you can configure these protocols to share routing information by configuring route redistribution in each protocol. For example, you can configure the Open Shortest Path First (OSPF) protocol to advertise routes learned from the Border Gateway Protocol (BGP). You can also redistribute static routes into any dynamic routing protocol. The router that is redistributing routes from another protocol sets a fixed route metric for those redistributed routes, which prevents incompatible route metrics between the different routing protocols. For example, routes redistributed from EIGRP into OSPF are assigned a fixed link cost metric that OSPF understands.

Note You are required to use route maps when you configure redistribution of routing information,

Route redistribution also uses an administrative distance (see the “Administrative Distance” section) to distinguish between routes learned from two different routing protocols. The preferred routing protocol is given a lower administrative distance so that its routes are picked over routes from another protocol with a higher administrative distance assigned.

Administrative Distance

An administrative distance is a rating of the trustworthiness of a routing information source. A higher value indicates a lower trust rating. Typically, a route can be learned through more than one protocol. Administrative distance is used to discriminate between routes learned from more than one protocol. The route with the lowest administrative distance is installed in the IP routing table.

Stub Routing

You can use stub routing in a hub-and-spoke network topology, where one or more end (stub) networks are connected to a remote router (the spoke) that is connected to one or more distribution routers (the hub). The remote router is adjacent only to one or more distribution routers. The only route for IP traffic to follow into the remote router is through a distribution router. This type of configuration is commonly used in WAN topologies in which the distribution router is directly connected to a WAN. The distribution router can be connected to many more remote routers. Often, the distribution router is connected to 100 or more remote routers. In a hub-and-spoke topology, the remote router must forward all nonlocal traffic to a distribution router, so it becomes unnecessary for the remote router to hold a complete routing table. Generally, the distribution router sends only a default route to the remote router.

Only specified routes are propagated from the remote (stub) router. The stub router responds to all queries for summaries, connected routes, redistributed static routes, external routes, and internal routes with the message “inaccessible.” A router that is configured as a stub sends a special peer information packet to all neighboring routers to report its status as a stub router.

Any neighbor that receives a packet that informs it of the stub status does not query the stub router for any routes, and a router that has a stub peer does not query that peer. The stub router depends on the distribution router to send the proper updates to all peers.

Figure 1-2 shows a simple hub-and-spoke configuration.

Figure 1-2 Simple Hub-and-Spoke Network

OSPF supports stub areas and EIGRP supports stub routers.

Routing Algorithms

Routing algorithms determine how a router gathers and reports reachability information, how it deals with topology changes, and how it determines the optimal route to a destination. Various types of routing algorithms exist, and each algorithm has a different impact on network and router resources. Routing algorithms use a variety of metrics that affect calculation of optimal routes. You can classify routing algorithms by type, such as static or dynamic, and interior or exterior.

This section includes the following topics:

- Static Routes and Dynamic Routing Protocols

- Interior and Exterior Gateway Protocols

- Distance Vector Protocols

- Link-State Protocols

Static Routes and Dynamic Routing Protocols

Static routes are route table entries that you manually configure. These static routes do not change unless you reconfigure them. Static routes are simple to design and work well in environments where network traffic is relatively predictable and where network design is relatively simple.

Because static routing systems cannot react to network changes, you should not use them for large, constantly changing networks. Most routing protocols today use dynamic routing algorithms that adjust to changing network circumstances by analyzing incoming routing update messages. If the message indicates that a network change has occurred, the routing software recalculates routes and sends out new routing update messages. These messages permeate the network, triggering routers to rerun their algorithms and change their routing tables accordingly.

You can supplement dynamic routing algorithms with static routes where appropriate. For example, you should configure each subnetwork with a static route to the IP default gateway or router of last resort (a router to which all unrouteable packets are sent).

Interior and Exterior Gateway Protocols

You can separate networks into unique routing domains or autonomous systems. An autonomous system is a portion of an internetwork under common administrative authority that is regulated by a particular set of administrative guidelines. Routing protocols that route between autonomous systems are called exterior gateway protocols or interdomain protocols. The Border Gateway Protocol (BGP) is an example of an exterior gateway protocol. Routing protocols used within an autonomous system are called interior gateway protocols or intradomain protocols. EIGRP and OSPF are examples of interior gateway protocols.

Distance Vector Protocols

Distance vector protocols use distance vector algorithms (also known as Bellman-Ford algorithms) that call for each router to send all or some portion of its routing table to its neighbors. Distance vector algorithms define routes by distance (for example, the number of hops to the destination) and direction (for example, the next-hop router). These routes are then broadcast to the directly connected neighbor routers. Each router uses these updates to verify and update the routing tables.

To prevent routing loops, most distance vector algorithms use split horizon with poison reverse which means that the routes learned from an interface are set as unreachable and advertised back along the interface that they were learned on during the next periodic update. This process prevents the router from seeing its own route updates coming back.

Distance vector algorithms send updates at fixed intervals but can also send updates in response to changes in route metric values. These triggered updates can speed up the route convergence time. The Routing Information Protocol (RIP) is a distance vector protocol.

Link-State Protocols

The link-state protocols, also known as shortest path first (SPF), share information with neighboring routers. Each router builds a link-state advertisement (LSA) that contains information about each link and directly connected neighbor router.

Each LSA has a sequence number. When a router receives an LSA and updates its link-state database, the LSA is flooded to all adjacent neighbors. If a router receives two LSAs with the same sequence number (from the same router), the router does not flood the last LSA that it received to its neighbors because it wants to prevent an LSA update loop. Because the router floods the LSAs immediately after it receives them, the convergence time for link-state protocols is minimized.

Discovering neighbors and establishing adjacency is an important part of a link state protocol. Neighbors are discovered using special Hello packets that also serve as keepalive notifications to each neighbor router. Adjacency is the establishment of a common set of operating parameters for the link-state protocol between neighbor routers.

The LSAs received by a router are added to the router’s link-state database. Each entry consists of the following parameters:

- Router ID (for the router that originated the LSA)

- Neighbor ID

- Link cost

- Sequence number of the LSA

- Age of the LSA entry

The router runs the SPF algorithm on the link-state database, building the shortest path tree for that router. This SPF tree is used to populate the routing table.

In link-state algorithms, each router builds a picture of the entire network in its routing tables. The link-state algorithms send small updates everywhere, while distance vector algorithms send larger updates only to neighboring routers.

Because they converge more quickly, link-state algorithms are less likely to cause routing loops than distance vector algorithms. However, link-state algorithms require more CPU power and memory than distance vector algorithms and they can be more expensive to implement and support. Link-state protocols are generally more scalable than distance vector protocols.

OSPF is an example of a link-state protocol.

Layer 3 Virtualization

Cisco NX-OS uses a virtual device context (VDC) to provide separate management domains per VDC and software fault isolation. Each VDC supports multiple virtual routing and forwarding instances and multiple routing information bases (RIBs) to support multiple address domains. Each VRF is associated with a RIB and this information is collected by the Forwarding Information Base (FIB). Figure 1-3 shows the relationship between a VDC, a VRF, and a Cisco NX-OS device.

Figure 1-3 Layer 3 Virtualization Example

A VRF represents a Layer 3 addressing domain. Each Layer 3 interface (logical or physical) belongs to one VRF. A VRF belongs to one VDC. Each VDC can support multiple VRFs. For more information, see Chapter14, “Configuring Layer 3 Virtualization”

See the Cisco Nexus 7000 Series NX-OS Virtual Device Context Configuration Guide, Release 5.x, for information about VDCs.

Cisco NX-OS Fowarding Architecture

The Cisco NX-OS forwarding architecture is responsible for processing all routing updates and populating the forwarding information to all modules in the chassis.

This section includes the following topics:

- Unicast RIB

- Adjacency Manager

- Unicast Forwarding Distribution Module

- FIB

- Hardware Forwarding

- Software Forwarding

Unicast RIB

The Cisco NX-OS forwarding architecture consists of multiple components, as shown in Figure 1-4.

Figure 1-4 Cisco NX-OS Forwarding Architecture

The unicast RIB exists on the active supervisor. It maintains the routing table with directly connected routes, static routes, and routes learned from dynamic unicast routing protocols. The unicast RIB also collects adjacency information from sources such as the Address Resolution Protocol (ARP). The unicast RIB determines the best next hop for a given route and populates the unicast FIB on the modules by using the services of the unicast FIB Distribution Module (FDM).

Each dynamic routing protocol must update the unicast RIB for any route that has timed out. The unicast RIB then deletes that route and recalculates the best next hop for that route (if an alternate path is available).

Adjacency Manager

The adjacency manager exists on the active supervisor and maintains adjacency information for different protocols including ARP, Neighbor Discovery Protocol (NDP), and static configuration. The most basic adjacency information is the Layer 3 to Layer 2 address mapping discovered by these protocols. Outgoing Layer 2 packets use the adjacency information to complete the Layer 2 header.

The adjacency manager can trigger ARP requests to find a particular Layer 3 to Layer 2 mapping. The new mapping becomes available when the corresponding ARP reply is received and processed. For IPv6, the adjacency manager finds the Layer 3 to Layer 2 mapping information from NDP. For more information, see Chapter3, “Configuring IPv6”

Unicast Forwarding Distribution Module

The unicast Forwarding Distribution Module (FDM) exists on the active supervisor and distributes the forwarding path information from the unicast RIB and other sources. The unicast RIB generates forwarding information that the unicast FIB programs into the hardware forwarding tables on the standby supervisor and the modules. The unicast FDM also downloads the FIB information to newly inserted modules.

The unicast FDM gathers adjacency information, rewrite information, and other platform-dependent information when updating routes in the unicast FIB. The adjacency and rewrite information consists of interface, next hop, and Layer 3 to Layer 2 mapping information. The interface and next-hop information is received in route updates from the unicast RIB. The Layer 3 to Layer 2 mapping is received from the adjacency manager.

FIB

The unicast FIB exists on supervisors and switching modules and builds the information used for the hardware forwarding engine. The unicast FIB receives route updates from the unicast FDM and sends the information to be programmed in the hardware forwarding engine. The unicast FIB controls the addition, deletion, and modification of routes, paths, and adjacencies.

The unicast FIBs are maintained on a per-VRF and per-address-family basis, that is, one for IPv4 and one for IPv6 for each configured VRF. Based on route update messages, the unicast FIB maintains a per-VRF prefix and next-hop adjacency information database. The next-hop adjacency data structure contains the next-hop IP address and the Layer 2 rewrite information. Multiple prefixes could share a next-hop adjacency information structure.

Hardware Forwarding

Cisco NX-OS supports distributed packet forwarding. The ingress port takes relevant information from the packet header and passes the information to the local switching engine. The local switching engine does the Layer 3 lookup and uses this information to rewrite the packet header. The ingress module forwards the packet to the egress port. If the egress port is on a different module, the packet is forwarded using the switch fabric to the egress module. The egress module does not participate in the Layer 3 forwarding decision.

The forwarding tables are identical on the supervisor and all the modules.

You also use the show platform fib or show platform forwarding commands to display details on hardware forwarding.

Software Forwarding

The software forwarding path in Cisco NX-OS is used mainly to handle features that are not supported in the hardware or to handle errors encountered during the hardware processing. Typically, packets with IP options or packets that need fragmentation are passed to the CPU on the active supervisor. All packets that should be switched in the software or terminated go to the supervisor. The supervisor uses the information provided by the unicast RIB and the adjacency manager to make the forwarding decisions. The module is not involved in the software forwarding path.

Software forwarding is controlled by control plane policies and rate limiters. For more information, see the Cisco Nexus 7000 Series NX-OS Security Configuration Guide, Release 5.x.

Layer 3 Interoperation with the N7K-F132-15 Module

Note You must install one of the N7K-M series modules in the Cisco Nexus 7000 Series chassis to run Layer 3 routing with the N7K-F132-15 module. You must have interfaces from both the M Series and the N7K-F132-15 modules in the same VDC. (See the Cisco Nexus 7000 Series NX-OS Virtual Device Context Configuration Guide, Release 5.x, for more information about VDCs.)

Layer 3 routing functionality comes up automatically when you have one of the N7K-M series modules installed in the chassis with the N7K-F132-15 module. You would usually position a chassis with both the N7K-F132-15 and M Series modules, or a mixed chassis, at the boundary between the Layer 2 and Layer 3 networks.

You must configure a VLAN interface for each VLAN on the N7K-F132-15 module that you want to use the proxy-routing functionality in a mixed chassis. (See the Cisco Nexus 7000 Series NX-OS Interfaces Configuration Guide, Release 5.x, for information about configuring VLAN interfaces.)

By default, all of the physical interfaces on the N7K-M series modules in the VDC become proxy routing ports for the VLANs that are configured with VLAN interfaces on the Layer 2-only N7K-F132-15 module in the same VDC. The physical interfaces on the M Series module can be administratively down and still pass traffic as proxy forwarding.

Packets that enter an interface on the N7K-F132-15 module are automatically forwarded to one of the interfaces on the M Series modules in the same VDC to be routed. The interface on the M Series module also performs egress replication for Layer 3 multicast packets that enter an interface on the N7K-F132-15 module in the same VDC.

Because the Layer 3 (proxy routing) traffic from the N7K-F132-15 modules adds to the traffic that the M Series modules are already processing, the device automatically provides load balancing for the total traffic load among the front panel ports of the available M Series modules in the VDC. If you add or remove interfaces to the M Series modules in the VDC, the device automatically rebalances the traffic. Note that proxy routing is sharing the forwarding capacity of the M Series modules. Removing interfaces reduces the amount of capacity available.

Instead of using the automatically configured proxy-routing interfaces on the M Series modules, you can optionally configure which interfaces on the M Series modules in the VDC performs proxy routing.

Summary of Layer 3 Unicast Routing Features

This section provides a brief introduction to the Layer 3 unicast features and protocols supported in Cisco NX-OS.

This section includes the following topics:

- IPv4 and IPv6

- IP Services

- OSPF

- EIGRP

- IS-IS

- BGP

- RIP

- Static Routing

- Layer 3 Virtualization

- Route Policy Manager

- Policy-Based Routing

- First Hop Redundancy Protocols

- Object Tracking

IPv4 and IPv6

Layer 3 uses either the IPv4 or IPv6 protocol. IPv6 is a new IP protocol designed to replace IPv4, the Internet protocol that is predominantly deployed and used throughout the world. IPv6 increases the number of network address bits from 32 bits (in IPv4) to 128 bits. For more information, see Chapter 2, “Configuring IPv4” or Chapter3, “Configuring IPv6”

IP Services

IP Services includes Dynamic Host Configuration Protocol (DHCP) and Domain Name System (DNS Client) clients. For more information, see Chapter4, “Configuring DNS”

OSPF

The Open Shortest Path First (OSPF) protocol is a link-state routing protocol used to exchange network reachability information within an autonomous system. Each OSPF router advertises information about its active links to its neighbor routers. Link information consists of the link type, the link metric, and the neighbor router that is connected to the link. The advertisements that contain this link information are called link-state advertisements. For more information, see Chapter6, “Configuring OSPFv2”

EIGRP

The Enhanced Interior Gateway Routing Protocol (EIGRP) is a unicast routing protocol that has the characteristics of both distance vector and link-state routing protocols. It is an improved version of IGRP, which is a Cisco proprietary routing protocol. EIGRP relies on its neighbors to provide the routesl. It constructs the network topology from the routes advertised by its neighbors, similar to a link-state protocol, and uses this information to select loop-free paths to destinations. For more information, see Chapter8, “Configuring EIGRP”

IS-IS

The Intermediate System-to-Intermediate System (IS-IS) protocol is an intradomain Open System Interconnection (OSI) dynamic routing protocol specified in the International Organization for Standardization (ISO) 10589. The IS-IS routing protocol is a link-state protocol. IS-IS features are as follows:

- Hierarchical routing

- Classless behavior

- Rapid flooding of new information

- Fast Convergence

- Very scalable

For more information, see Chapter9, “Configuring IS-IS”

BGP

The Border Gateway Protocol (BGP) is an inter-autonomous system routing protocol. A BGP router advertises network reachability information to other BGP routers using Transmission Control Protocol (TCP) as its reliable transport mechanism. The network reachability information includes the destination network prefix, a list of autonomous systems that needs to be traversed to reach the destination, and the next-hop router. Reachability information contains additional path attributes such as preference to a route, origin of the route, community and others. For more information, see Chapter 10, “Configuring Basic BGP” and Chapter11, “Configuring Advanced BGP”

RIP

The Routing Information Protocol (RIP) is a distance-vector protocol that uses a hop count as its metric. RIP is widely used for routing traffic in the global Internet and is an Interior Gateway Protocol (IGP), which means that it performs routing within a single autonomous system. For more information, see Chapter12, “Configuring RIP”

Static Routing

Static routing allows you to enter a fixed route to a destination. This feature is useful for small networks where the topology is simple. Static routing is also used with other routing protocols to control default routes and route distribution. For more information, see Chapter13, “Configuring Static Routing”

Layer 3 Virtualization

Virtualization allows you to share physical resources across separate management domains. Cisco NX-OS supports Virtual Device Contexts (VDCs) that allow you to create separate virtual systems within a Cisco NX-OS system. Each VDC is isolated from the others, which means that a problem in one VDC does not affect any other VDCs. VDCs are also secure from each other. You can assign separate network operators to each VDC and these network operators cannot control or view the configuration of a different VDC.

Cisco NX-OS also supports Layer 3 virtualization with virtual routing and forwarding (VRF). VRF provides a separate address domain for configuring Layer 3 routing protocols. For more information, see Chapter14, “Configuring Layer 3 Virtualization”

Route Policy Manager

The Route Policy Manager provides a route filtering capability in Cisco NX-OS. It uses route maps to filter routes distributed across various routing protocols and between different entities within a given routing protocol. Filtering is based on specific match criteria, which is similar to packet filtering by access control lists. For more information, see Chapter16, “Configuring Route Policy Manager”

Policy-Based Routing

Policy-based routing uses the Route Policy Manager to create policy route filters. These policy route filters can forward a packet to a specified next hop based on the source of the packet or other fields in the packet header. Policy routes can be linked to extended IP access lists so that routing might be based on protocol types and port numbers. For more information, see Chapter17, “Configuring Policy-Based Routing”

First Hop Redundancy Protocols

First hop redundancy protocols (FHRP), such as Gateway Load Balancing Protocol (GLBP), Hot Standby Router Protocol (HSRP), and Virtual Router Redundancy Protocol (VRRP), allow you to provide redundant connections to your hosts. If an active first-hop router fails, the FHRP automatically selects a standby router to take over. You do not need to update the hosts with new IP addresses since the address is virtual and shared between each router in the FHRP group. For more information on GLBP, see Chapter 18, “Configuring GLBP”. For more information on HSRP, see Chapter 19, “Configuring HSRP”. For more information on VRRP, see Chapter 20, “Configuring VRRP”.

Object Tracking

Object tracking allows you to track specific objects on the network, such as the interface line protocol state, IP routing, and route reachability, and take action when the tracked object’s state changes. This feature allows you to increase the availability of the network and shorten the recovery time if an object state goes down. For more information, see Chapter 21, “Configuring Object Tracking”.

Related Topics

The following Cisco documents are related to the Layer 3 features:

- Cisco Nexus 7000 Series NX-OS Multicast Routing Configuration Guide, Release 5.x

- Cisco Nexus 7000 Series NX-OS High Availability and Redundancy Guide, Release 5.x

- Cisco Nexus 7000 Series NX-OS Virtual Device Context Configuration Guide, Release 5.x

- Exploring Autonomous System Numbers: http://www.cisco.com/web/about/ac123/ac147/archived_issues/ipj_9-1/autonomous_system_numbers.html

Configuring IPv4

This chapter describes how to configure Internet Protocol version 4 (IPv4), which includes addressing, Address Resolution Protocol (ARP), and Internet Control Message Protocol (ICMP), on the Cisco NX-OS device.

This chapter includes the following sections:

- Information About IPv4

- Licensing Requirements for IPv4

- Prerequisites for IPv4

- Guidelines and Limitations for IPv4

- Default Settings

- Configuring IPv4

- Configuration Examples for IPv4

- Additional References

- Feature History for IP

Information About IPv4

You can configure IP on the device to assign IP addresses to network interfaces. When you assign IP addresses, you enable the interfaces and allow communication with the hosts on those interfaces.

You can configure an IP address as primary or secondary on a device. An interface can have one primary IP address and multiple secondary addresses. All networking devices on an interface should share the same primary IP address because the packets that are generated by the device always use the primary IPv4 address. Each IPv4 packet is based on the information from a source or destination IP address. For more information, see the “Multiple IPv4 Addresses” section.

You can use a subnet to mask the IP addresses. A mask is used to determine what subnet an IP address belongs to. An IP address contains the network address and the host address. A mask identifies the bits that denote the network number in an IP address. When you use the mask to subnet a network, the mask is then referred to as a subnet mask. Subnet masks are 32-bit values that allow the recipient of IP packets to distinguish the network ID portion of the IP address from the host ID portion of the IP address.

The IP feature is responsible for handling IPv4 packets that terminate in the supervisor module, as well as forwarding of IPv4 packets, which includes IPv4 unicast/multicast route lookup, reverse path forwarding (RPF) checks, and software access control list/policy-based routing (ACL/PBR) forwarding. The IP feature also manages the network interface IP address configuration, duplicate address checks, static routes, and packet send/receive interface for IP clients.

This section includes the following topics:

- Multiple IPv4 Addresses

- Address Resolution Protocol

- ARP Caching

- Static and Dynamic Entries in the ARP Cache

- Devices That Do Not Use ARP

- Reverse ARP

- Proxy ARP

- Local Proxy ARP

- Gratuitous ARP

- Glean Throttling

- Path MTU Discovery

- ICMP

- Virtualization Support

Multiple IPv4 Addresses

Cisco NX-OS supports multiple IP addresses per interface. You can specify an unlimited number of secondary addresses for a variety of situations. The most common are as follows:

- When there are not enough host IP addresses for a particular network interface. For example, if your subnetting allows up to 254 hosts per logical subnet, but on one physical subnet you must have 300 host addresses, then you can use secondary IP addresses on the routers or access servers to allow you to have two logical subnets that use one physical subnet.

- Two subnets of a single network might otherwise be separated by another network. You can create a single network from subnets that are physically separated by another network by using a secondary address. In these instances, the first network is extended, or layered on top of the second network. A subnet cannot appear on more than one active interface of the router at a time.

Note If any device on a network segment uses a secondary IPv4 address, all other devices on that same network interface must also use a secondary address from the same network or subnet. The inconsistent use of secondary addresses on a network segment can quickly cause routing loops.

Address Resolution Protocol

Networking devices and Layer 3 switches use Address Resolution Protocol (ARP) to map IP (network layer) addresses to (Media Access Control [MAC]-layer) addresses to enable IP packets to be sent across networks. Before a device sends a packet to another device, it looks in its own ARP cache to see if there is a MAC address and corresponding IP address for the destination device. If there is no entry, the source device sends a broadcast message to every device on the network.

Each device compares the IP address to its own. Only the device with the matching IP address replies to the device that sends the data with a packet that contains the MAC address for the device. The source device adds the destination device MAC address to its ARP table for future reference, creates a data-link header and trailer that encapsulates the packet, and proceeds to transfer the data. Figure 2-1 shows the ARP broadcast and response process.

Figure 2-1 ARP Process

When the destination device lies on a remote network that is beyond another device, the process is the same except that the device that sends the data sends an ARP request for the MAC address of the default gateway. After the address is resolved and the default gateway receives the packet, the default gateway broadcasts the destination IP address over the networks connected to it. The device on the destination device network uses ARP to obtain the MAC address of the destination device and delivers the packet. ARP is enabled by default.

The default system-defined CoPP policy rate limits ARP broadcast packets bound for the supervisor module. The default system-defined CoPP policy prevents an ARP broadcast storm from affecting the control plane traffic but does not affect bridged packets.

Note Cisco Nexus 7000 Series devices do not support Ethernet SNAP encoding.

ARP Caching

ARP caching minimizes broadcasts and limits wasteful use of network resources. The mapping of IP addresses to MAC addresses occurs at each hop (device) on the network for every packet sent over an internetwork, which may affect network performance.

ARP caching stores network addresses and the associated data-link addresses in the memory for a period of time, which minimizes the use of valuable network resources to broadcast for the same address each time that a packet is sent. You must maintain the cache entries that are set to expire periodically because the information might become outdated. Every device on a network updates its tables as addresses are broadcast.

Static and Dynamic Entries in the ARP Cache

Static routing requires that you manually configure the IP addresses, subnet masks, gateways, and corresponding MAC addresses for each interface of each device. Static routing requires more work to maintain the route table. You must update the table each time you add or change routes.

Dynamic routing uses protocols that enable the devices in a network to exchange routing table information with each other. Dynamic routing is more efficient than static routing because the route table is automatically updated unless you add a time limit to the cache. The default time limit is 25 minutes but you can modify the time limit if the network has many routes that are added and deleted from the cache.

Devices That Do Not Use ARP

When a network is divided into two segments, a bridge joins the segments and filters traffic to each segment based on MAC addresses. The bridge builds its own address table, which uses MAC addresses only. A device has an ARP cache that contains both IP addresses and the corresponding MAC addresses.

Passive hubs are central-connection devices that physically connect other devices in a network. They send messages out on all their ports to the devices and operate at Layer 1 but do not maintain an address table.

Layer 2 switches determine which port is connected to a device to which the message is addressed and sent only to that port. However, Layer 3 switches are devices that build an ARP cache (table).

Reverse ARP

Reverse ARP (RARP) as defined by RFC 903 works the same way as ARP, except that the RARP request packet requests an IP address instead of a MAC address. RARP often is used by diskless workstations because this type of device has no way to store IP addresses to use when they boot. The only address that is known is the MAC address because it is burned into the hardware.

Use of RARP requires an RARP server on the same network segment as the router interface. Figure 2-2 illustrates how RARP works.

Figure 2-2 Reverse ARP

RARP has several limitations. Because of these limitations, most businesses use DHCP to assign IP addresses dynamically. DHCP is cost effective and requires less maintenance than RARP. The following are the most important limitations:

- Since RARP uses hardware addresses, if the internetwork is large with many physical networks, a RARP server must be on every segment with an additional server for redundancy. Maintaining two servers for every segment is costly.

- Each server must be configured with a table of static mappings between the hardware addresses and IP addresses. Maintenance of the IP addresses is difficult.

- RARP only provides IP addresses of the hosts and not subnet masks or default gateways.

Proxy ARP

Proxy ARP enables a device that is physically located on one network appear to be logically part of a different physical network connected to the same device or firewall. Proxy ARP allows you to hide a device with a public IP address on a private network behind a router and still have the device appear to be on the public network in front of the router. By hiding its identity, the router accepts responsibility for routing packets to the real destination. Proxy ARP can help devices on a subnet reach remote subnets without configuring routing or a default gateway.

When devices are not in the same data link layer network but in the same IP network, they try to transmit data to each other as if they are on the local network. However, the router that separates the devices does not send a broadcast message because routers do not pass hardware-layer broadcasts and the addresses cannot be resolved.

When you enable Proxy ARP on the device and it receives an ARP request, it identifies the request as a request for a system that is not on the local LAN. The device responds as if it is the remote destination for which the broadcast is addressed, with an ARP response that associates the device’s MAC address with the remote destination's IP address. The local device believes that it is directly connected to the destination, while in reality its packets are being forwarded from the local subnetwork toward the destination subnetwork by their local device. By default, Proxy ARP is disabled.

Local Proxy ARP

You can use local Proxy ARP to enable a device to respond to ARP requests for IP addresses within a subnet where normally no routing is required. When you enable local Proxy ARP, ARP responds to all ARP requests for IP addresses within the subnet and forwards all traffic between hosts in the subnet. Use this feature only on subnets where hosts are intentionally prevented from communicating directly by the configuration on the device to which they are connected.

Gratuitous ARP

Gratuitous ARP sends a request with an identical source IP address and a destination IP address to detect duplicate IP addresses. Cisco NX-OS Release 4.0(3) and later releases support enabling or disabling gratuitous ARP requests or ARP cache updates.

Glean Throttling

When forwarding an incoming IP packet in a line card, if the Address Resolution Protocol (ARP) request for the next hop is not resolved, the line card forwards the packets to the supervisor (glean throttling). The supervisor resolves the MAC address for the next hop and programs the hardware.

The Cisco Nexus 7000 Series device hardware has glean rate limiters to protect the supervisor from the glean traffic. If the maximum number of entries is exceeded, the packets for which the ARP request is not resolved continues to be processed in the software instead of getting dropped in the hardware.

When an ARP request is sent, the software adds a /32 drop adjacency in the hardware to prevent the packets to the same next-hop IP address to be forwarded to the supervisor. When the ARP is resolved, the hardware entry is updated with the correct MAC address. If the ARP entry is not resolved before a timeout period, the entry is removed from the hardware.

Path MTU Discovery

Path maximum transmission unit (MTU) discovery is a method for maximizing the use of available bandwidth in the network between the endpoints of a TCP connection. It is described in RFC 1191. Existing connections are not affected when this feature is turned on or off.

Note Please ensure you enable ip unreachables command between TCP endpoints for the Path MTU discovery feature to work correctly.

ICMP

You can use the Internet Control Message Protocol (ICMP) to provide message packets that report errors and other information that is relevant to IP processing. ICMP generates error messages, such as ICMP destination unreachable messages, ICMP Echo Requests (which send a packet on a round trip between two hosts) and Echo Reply messages. ICMP also provides many diagnostic functions and can send and redirect error packets to the host. By default, ICMP is enabled.

Some of the ICMP message types are as follows:

- Network error messages

- Network congestion messages

- Troubleshooting information

- Timeout announcements

Note ICMP redirects are disabled on interfaces where the local proxy ARP feature is enabled.

Virtualization Support

IPv4 supports virtual routing and forwarding (VRF) instances. VRFs exist within virtual device contexts (VDCs). By default, Cisco NX-OS places you in the default VDC and default VRF unless you specifically configure another VDC and VRF. For more information, see the Cisco NX-OS Virtual Device Context Configuration Guide and see Chapter14, “Configuring Layer 3 Virtualization”

Licensing Requirements for IPv4

The following table shows the licensing requirements for this feature:

Product

License Requirement

Cisco NX-OS

IP requires no license. Any feature not included in a license package is bundled with the Cisco NX-OS system images and is provided at no extra charge to you. For a complete explanation of the Cisco NX-OS licensing scheme, see the Cisco NX-OS Licensing Guide.

Prerequisites for IPv4

IPv4 has the following prerequisites:

- IPv4 can only be configured on Layer 3 interfaces.

Guidelines and Limitations for IPv4

IPv4 has the following configuration guidelines and limitations:

- You can configure a secondary IP address only after you configure the primary IP address.

- Cisco Nexus 7000 Series devices do not support Ethernet SNAP encoding.

Default Settings

Table 2-1 Default IP Parameters

Parameters

Default

ARP timeout

1500 seconds

proxy ARP

Disabled

Configuring IPv4

This section includes the following topics:

- Configuring IPv4 Addressing

- Configuring Multiple IP Addresses

- Configuring a Static ARP Entry

- Configuring Proxy ARP

- Configuring Local Proxy ARP

- Configuring Gratuitous ARP

- Configuring Path MTU Discovery

- Configuring IP Packet Verification

- Configuring IP Directed Broadcasts

- Configuring IP Glean Throttling

- Configuring the Hardware IP Glean Throttle Maximum

- Configuring a Hardware IP Glean Throttle Timeout

- Configuring the Hardware IP Glean Throttle Syslog

Note If you are familiar with the Cisco IOS CLI, be aware that the Cisco NX-OS commands for this feature might differ from the Cisco IOS commands that you would use.

Configuring IPv4 Addressing

You can assign a primary IP address for a network interface.

BEFORE YOU BEGIN

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. interface ethernet number

3. ip address ip-address/length

4. (Optional) show ip interface

5. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

interface ethernet number

Example:

switch(config)# interface ethernet 2/3

switch(config-if)#

Enters interface configuration mode.

Step 3

ip address ip-address/length

[secondary]

Example:

switch(config-if)# ip address 192.168.1.1 255.0.0.0

Specifies a primary or secondary IPv4 address for an interface.

- The network mask can be a four-part dotted decimal address. For example, 255.0.0.0 indicates that each bit equal to 1 means the corresponding address bit belongs to the network address.

- The network mask can be indicated as a slash (/) and a number - a prefix length. The prefix length is a decimal value that indicates how many of the high-order contiguous bits of the address comprise the prefix (the network portion of the address). A slash must precede the decimal value and there is no space between the IP address and the slash.

Step 4

show ip interface

Example:

switch(config-if)# show ip interface

(Optional) Displays interfaces configured for IPv4.

Step 5

copy running-config startup-config

Example:

switch(config-if)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to assign an IPv4 address:

switch# configure terminal

switch(config)# interface ethernet 2/3

switch(config-if)# ip address 192.168.1.1 255.0.0.0

switch(config-if)# copy running-config startup-config

Configuring Multiple IP Addresses

You can only add secondary IP addresses after you configure primary IP addresses.

BEFORE YOU BEGIN

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. interface ethernet number

3. ip address ip-address/length

4. (Optional) show ip interface

5. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

interface ethernet number

Example:

switch(config)# interface ethernet 2/3

switch(config-if)#

Enters interface configuration mode.

Step 3

ip address ip-address/length

[secondary]

Example:

switch(config-if)# ip address 192.168.1.1 255.0.0.0 secondary

Specifies the configured address as a secondary IPv4 address.

Step 4

show ip interface

Example:

switch(config-if)# show ip interface

(Optional) Displays interfaces configured for IPv4.

Step 5

copy running-config startup-config

Example:

switch(config-if)# copy running-config startup-config

(Optional) Saves this configuration change.

Configuring a Static ARP Entry

You can configure a static ARP entry on the device to map IP addresses to MAC hardware addresses, including static multicast MAC addresses.

BEFORE YOU BEGIN

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. interface ethernet number

3. ip arp ipaddr mac_addr

4. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

interface ethernet number

Example:

switch(config)# interface ethernet 2/3

switch(config-if)#

Enters interface configuration mode.

Step 3

ip arp ipaddr mac_addr

Example:

switch(config-if)# ip arp 192.168.1.1 0019.076c.1a78

Associates an IP address with a MAC address as a static entry.

Step 4

copy running-config startup-config

Example:

switch(config-if)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to configure a static ARP entry:

switch# configure terminal

switch(config)# interface ethernet 2/3

switch(config-if)# ip arp 192.168.1.1 0019.076c.1a78

switch(config-if)# copy running-config startup-config

Configuring Proxy ARP

You can configure Proxy ARP on the device to determine the media addresses of hosts on other networks or subnets.

BEFORE YOU BEGIN

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. interface ethernet number

3. ip proxy-arp

4. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

interface ethernet number

Example:

switch(config)# interface ethernet 2/3

switch(config-if)#

Enters interface configuration mode.

Step 3

ip proxy-arp

Example:

switch(config-if)# ip proxy-arp

Enables Proxy ARP on the interface.

Step 4

copy running-config startup-config

Example:

switch(config-if)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to configure Proxy ARP:

switch# configure terminal

switch(config)# interface ethernet 2/3

switch(config-if)# ip proxy-arp

switch(config-if)# copy running-config startup-config

Configuring Local Proxy ARP

You can configure Local Proxy ARP on the device.

BEFORE YOU BEGIN

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. interface ethernet number

3. ip local-proxy-arp

4. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

interface ethernet number

Example:

switch(config)# interface ethernet 2/3

switch(config-if)#

Enters interface configuration mode.

Step 3

ip local-proxy-arp

Example:

switch(config-if)# ip local-proxy-arp

Enables Local Proxy ARP on the interface.

Step 4

copy running-config startup-config

Example:

switch(config-if)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to configure Local Proxy ARP:

switch# configure terminal

switch(config)# interface ethernet 2/3

switch(config-if)# ip local-proxy-arp

switch(config-if)# copy running-config startup-config

Configuring Gratuitous ARP

You can configure gratuitous ARP on an interface.

BEFORE YOU BEGIN

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. interface ethernet number

3. ip arp gratuitous {request | update}

4. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

interface ethernet number

Example:

switch(config)# interface ethernet 2/3

switch(config-if)#

Enters interface configuration mode.

Step 3

ip arp gratuitous {request | update}

Example:

switch(config-if)# ip arp gratuitous request

Enables gratuitous ARP on the interface. The default is enabled.

Step 4

copy running-config startup-config

Example:

switch(config-if)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to disable gratuitous ARP requests:

switch# configure terminal

switch(config)# interface ethernet 2/3

switch(config-if)# no ip arp gratuitous request

switch(config-if)# copy running-config startup-config

Configuring Path MTU Discovery

You can configure path MTU discovery.

BEFORE YOU BEGIN

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. ip tcp path-mtu-discovery

3. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

ip tcp path-mtu-discovery

Example:

switch(config)# ip tcp path-mtu-discovery

Enables path MTU discovery.

Step 3

copy running-config startup-config

Example:

switch(config)# copy running-config startup-config

(Optional) Saves this configuration change.

Configuring IP Packet Verification

Cisco NX-OS supports an Intrusion Detection System (IDS) that checks for IP packet verification. You can enable or disable these IDS checks.

Command

Purpose

hardware ip verify address {destination zero | identical | reserved | source {broadcast | multicast}}

Performs the following IDS checks on the IP address:

- destination zero —Drops IP packets if the destination IP address is 0.0.0.0.

- identical —Drops IP packets if the source IP address is identical to the destination IP address.

- reserved —Drops IP packets if the IP address is in the 127.x.x.x range.

- source —Drops IP packets if the IP source address is either 255.255.255.255 (broadcast) or in the 224.x.x.x range (multicast).

hardware ip verify checksum

Drops IP packets if the packet checksum is invalid.

hardware ip verify fragment

Drops IP packets if the packet fragment has a nonzero offset and the DF bit is active.

hardware ip verify length {consistent | maximum {max-frag | max-tcp | udp} | minimum}

Performs the following IDS checks on the IP address:

- consistent —Drops IP packets where the Ethernet frame size is greater than or equal to the IP packet length plus the Ethernet header.

- maximum max-frag —Drops IP packets if the maximum fragment offset is greater than 65536.

- maximum max-tcp —Drops IP packets if the TCP length is greater than the IP payload length.

- maximum udp —Drops IP packets if the IP payload length is less than the UDP packet length.

- minimum —Drops IP packets if the Ethernet frame length is less than the IP packet length plus four octets (the CRC length).

hardware ip verify tcp tiny-frag

Drops TCP packets if the IP fragment offset is 1, or if the IP fragment offset is 0 and the IP payload length is less than 16.

hardware ip verify version

Drops IP packets if the ethertype is not set to 4 (IPv4).

Use the show hardware forwarding ip verify command to display the IP packet verification configuration.

Configuring IP Directed Broadcasts

An IP directed broadcast is an IP packet whose destination address is a valid broadcast address for some IP subnet but which originates from a node that is not itself part of that destination subnet.

A device that is not directly connected to its destination subnet forwards an IP directed broadcast in the same way it forwards unicast IP packets destined to a host on that subnet. When a directed broadcast packet reaches a device that is directly connected to its destination subnet, that packet is broadcast on the destination subnet. The destination address in the IP header of the packet is rewritten to the configured IP broadcast address for the subnet, and the packet is sent as a link-layer broadcast.

If directed broadcast is enabled for an interface, incoming IP packets whose addresses identify them as directed broadcasts intended for the subnet to which that interface is attached are broadcasted on that subnet. You can optionally filter those broacasts through an IP access list such that only those packets that pass through the access list are broadcasted on the subnet.

To enable IP directed broadcasts, use the following command in interface configuration mode:

Command

Purpose

ip directed-broadcast [acl]

Enables the translation of a directed broadcast to physical broadcasts. You can optionally filter those broacasts through an IP access list.

Configuring IP Glean Throttling

Cisco NX-OS software supports glean throttling rate limiters to protect the supervisor from the glean traffic.

You can enable IP glean throttling.

Note We recommend that you configure the IP glean throttle feature by using the hardware ip glean throttle command to filter the unnecessary glean packets that are sent to the supervisor for ARP resolution for the next hops that are not reachable or do not exist. IP glean throttling boosts software performance and helps to manage traffic more efficiently.

BEFORE YOU BEGIN

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. hardware ip glean throttle

3. no hardware ip glean throttle

4. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

hardware ip glean throttle

Example:

switch(config)# hardware ip glean throttle

Enables ARP throttling.

Step 3

no hardware ip glean throttle

Example:

switch(config)# no hardware ip glean throttle

Disables ARP throttling.

Step 4

copy running-config startup-config

Example:

switch(config)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to enable IP glean throttling:

switch# configure terminal

switch(config)# hardware ip glean throttle

switch(config-if)# copy running-config startup-config

Configuring the Hardware IP Glean Throttle Maximum

You can limit the maximum number of drop adjacencies that are installed in the Forwarding Information Base (FIB).

BEFORE YOU BEGIN

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. hardware ip glean throttle maximum count

3. no hardware ip glean throttle maximum count

4. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

hardware ip glean throttle maximum count

Example:

switch(config)# hardware ip glean throttle maximum 2134

Configures the number of drop adjacencies that are installed in the FIB.

Step 3

no hardware ip glean throttle maximum count

Example:

switch(config)# no hardware ip glean throttle maximum 2134

Applies the default limits.

The default value is 1000. The range is from 0 to 32767 entries.

Step 4

copy running-config startup-config

Example:

switch(config)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to limit the maximum number of drop adjacencies that are installed in the FIB:

switch# configure terminal

switch(config)# hardware ip glean throttle maximum 2134

switch(config-if)# copy running-config startup-config

Configuring a Hardware IP Glean Throttle Timeout

You can configure a timeout for the installed drop adjacencies to remain in the FIB.

BEFORE YOU BEGIN

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. hardware ip glean throttle maximum timeout timeout-in-sec

3. no hardware ip glean throttle maximum timeout timeout-in-sec

4. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

hardware ip glean throttle maximum timeout timeout-in-sec

Example:

switch(config)# hardware ip glean throttle maximum timeout 300

Configures the timeout for the installed drop adjacencies to remain in the FIB.

Step 3

no hardware ip glean throttle maximum timeout timeout-in-sec

Example:

switch(config)# no hardware ip glean throttle maximum timeout 300

Applies the default limits.

The timeout value is in seconds. The range is from 300 seconds (5 minutes) to 1800 seconds (30 minutes).

Note After the timeout period is exceeded, the drop adjacencies are removed from the FIB.

Step 4

copy running-config startup-config

Example:

switch(config)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to configure a timeout for the drop adjacencies that are installed.

switch# configure terminal

switch(config)# hardware ip glean throttle maximum timeout 300

switch(config-if)# copy running-config startup-config

Configuring the Hardware IP Glean Throttle Syslog

You can generate a syslog if the number of packets that get dropped for a specific flow exceeds the configured packet count.

BEFORE YOU BEGIN

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. hardware ip glean throttle syslog pck-count

3. no hardware ip glean throttle syslog pck-count

4. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

hardware ip glean throttle syslog pck-count

Example:

switch(config)# hardware ip glean throttle syslog 1030

Generates a syslog if the number of packets that get dropped for a specific flow exceed the configured packet count.

Step 3

no hardware ip glean throttle syslog pck-count

Example:

switch(config)# no hardware ip glean throttle syslog 1030

Applies the default limits.

The default is 10000 packets. The range is from 0 to 65535 packets.

Note After the timeout period is exceeded, the drop adjacencies are removed from the FIB.

Step 4

copy running-config startup-config

Example:

switch(config)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to generate a syslog if the number of packets that get dropped for a specific flow exceeds the configured packet count:

switch# configure terminal

switch(config)# hardware ip glean throttle syslog 1030

switch(config-if)# copy running-config startup-config

Verifying the IPv4 Configuration

Command

Purpose

show hardware forwarding ip verify

Displays the IP packet verification configuration.

show ip adjacency

Displays the adjacency table.

show ip adjacency summary

Displays the summary of number of throttle adjacencies.

show ip arp

Displays the ARP table.

show ip arp summary

Displays the summary of the number of throttle adjacencies.

show ip adjacency throttle statistics

Displays only the throttled adjacencies.

show ip interface

Displays IP-related interface information.

show ip arp statistics [vrf vrf-name]

Displays the ARP statistics.

Configuration Examples for IPv4

The N7K-F132-15 module only runs Layer 2 switching. So, when you have both this module and an M Series module in one Nexus 7000 Series chassis and you are performing Layer 3 procedures, the system uses proxy routing. You can also configure proxy routing.

This section includes the following topics:

- Example: Reserving All Ports on a Module for Proxy Routing

- Example: Reserving Ports for Proxy Routing

- Example: Excluding Ports From Proxy Routing

Example: Reserving All Ports on a Module for Proxy Routing

This example shows how to reserve all ports on a module for proxy routing.

Step 1 Determine which modules are present in the device.

switch# show module

Mod Ports Module-Type Model Status

--- ----- -------------------------------- ------------------ ------------

1 32 10 Gbps Ethernet Module N7K-M132XP-12 ok

2 48 10/100/1000 Mbps Ethernet Module N7K-M148GT-11 ok

3 48 1000 Mbps Optical Ethernet Modul N7K-M148GS-11 ok

5 0 Supervisor module-1X N7K-SUP1 active *

6 0 Supervisor module-1X N7K-SUP1 ha-standby

8 32 1/10 Gbps Ethernet Module N7K-F132XP-15 ok

The F1 module is in Slot 8, and the M1 modules are in Slots 1 - 3.

Step 2 Determine which ports are available in the VDC.

switch# show vdc membership | end "Ethernet3/48"

vdc_id: 0 vdc_name: Unallocated interfaces:

vdc_id: 1 vdc_name: switch interfaces:

Ethernet1/9 Ethernet1/10 Ethernet1/11

Ethernet1/12 Ethernet1/13 Ethernet1/14

Ethernet1/15 Ethernet1/16 Ethernet1/17

Ethernet1/18 Ethernet1/19 Ethernet1/20

Ethernet1/21 Ethernet1/22 Ethernet1/23

Ethernet1/24 Ethernet1/25 Ethernet1/26

Ethernet1/27 Ethernet1/28 Ethernet1/29

Ethernet1/30 Ethernet1/31 Ethernet1/32

Ethernet2/1 Ethernet2/2 Ethernet2/3

Ethernet2/4 Ethernet2/5 Ethernet2/6

Ethernet2/7 Ethernet2/8 Ethernet2/9

Ethernet2/10 Ethernet2/11 Ethernet2/12

Ethernet2/25 Ethernet2/26 Ethernet2/27

Ethernet2/28 Ethernet2/29 Ethernet2/30

Ethernet2/31 Ethernet2/32 Ethernet2/33

Ethernet2/34 Ethernet2/35 Ethernet2/36

Ethernet2/37 Ethernet2/38 Ethernet2/39

Ethernet2/40 Ethernet2/41 Ethernet2/42

Ethernet2/43 Ethernet2/44 Ethernet2/45

Ethernet2/46 Ethernet2/47 Ethernet2/48

Ethernet3/1 Ethernet3/2 Ethernet3/3

Ethernet3/4 Ethernet3/5 Ethernet3/6

Ethernet3/7 Ethernet3/8 Ethernet3/9

Ethernet3/10 Ethernet3/11 Ethernet3/12

Ethernet3/13 Ethernet3/14 Ethernet3/15

Ethernet3/16 Ethernet3/17 Ethernet3/18

Ethernet3/19 Ethernet3/20 Ethernet3/21

Ethernet3/22 Ethernet3/23 Ethernet3/24

Ethernet3/25 Ethernet3/26 Ethernet3/27

Ethernet3/28 Ethernet3/29 Ethernet3/30

Ethernet3/31 Ethernet3/32 Ethernet3/33

Ethernet3/34 Ethernet3/35 Ethernet3/36

Ethernet3/37 Ethernet3/38 Ethernet3/39

Ethernet3/40 Ethernet3/41 Ethernet3/42

Ethernet3/43 Ethernet3/44 Ethernet3/45

Ethernet3/46 Ethernet3/47 Ethernet3/48

Step 3 Determine which ports are available for proxy routing.

switch# show hardware proxy layer-3 detail

Global Information:

F1 Modules: Count: 1 Slot: 8

M1 Modules: Count: 3 Slot: 1-3

Replication Rebalance Mode: Manual

Number of proxy layer-3 forwarders: 13

Number of proxy layer-3 replicators: 8

Forwarder Interfaces Status Reason

------------------------------------------------------------------------------

Eth1/9, Eth1/11, Eth1/13, Eth1/15 up SUCCESS

Eth1/10, Eth1/12, Eth1/14, Eth1/16 up SUCCESS

Eth1/17, Eth1/19, Eth1/21, Eth1/23 up SUCCESS

Eth1/18, Eth1/20, Eth1/22, Eth1/24 up SUCCESS

Eth1/25, Eth1/27, Eth1/29, Eth1/31 up SUCCESS

Eth1/26, Eth1/28, Eth1/30, Eth1/32 up SUCCESS

Eth2/1-12 up SUCCESS

Eth2/25-36 up SUCCESS

Eth2/37-48 up SUCCESS

Eth3/1-12 up SUCCESS

Eth3/13-24 up SUCCESS

Eth3/25-36 up SUCCESS

Eth3/37-48 up SUCCESS

Replicator Interfaces #Interface-Vlan Interface-Vlan

------------------------------------------------------------------------------

Eth1/1, Eth1/3, Eth1/5, Eth1/7, Eth1/9, 0

Eth1/11, Eth1/13, Eth1/15

Eth1/2, Eth1/4, Eth1/6, Eth1/8, Eth1/10, 0

Eth1/12, Eth1/14, Eth1/16

Eth1/17, Eth1/19, Eth1/21, Eth1/23, 0

Eth1/25, Eth1/27, Eth1/29, Eth1/31

Eth1/18, Eth1/20, Eth1/22, Eth1/24, 0

Eth1/26, Eth1/28, Eth1/30, Eth1/32

Eth2/1-24 0

Eth2/25-48 0

Eth3/1-24 0

Eth3/25-48 0

switch#

Note Ports are listed in their respective port-groups.

Step 4 Reserve a module for unicast and multicast proxy routing.

switch# configure terminal

switch(config)# hardware proxy layer-3 forwarding use module 2

switch(config)# hardware proxy layer-3 replication use module 2

Step 5 Verify this configuration.

switch(config)# show hardware proxy layer-3 detail

Global Information:

F1 Modules: Count: 1 Slot: 8

M1 Modules: Count: 3 Slot: 1-3

Replication Rebalance Mode: Manual

Number of proxy layer-3 forwarders: 3

Number of proxy layer-3 replicators: 2

Forwarder Interfaces Status Reason

------------------------------------------------------------------------------

Eth2/1-12 up SUCCESS

Eth2/25-36 up SUCCESS

Eth2/37-48 up SUCCESS

Replicator Interfaces #Interface-Vlan Interface-Vlan

------------------------------------------------------------------------------

Eth2/1-24 0

Eth2/25-48 0

switch(config)#

Example: Reserving Ports for Proxy Routing

This example shows how to reserve some ports on a module for proxy routing.

Step 1 Reserve a subset of ports on a module.

switch(config)# hardware proxy layer-3 forwarding use interface ethernet 2/1-6 <---- -subset of port group

switch(config)# hardware proxy layer-3 replication use interface ethernet 2/1-6 <---- -subset of port group

This example reserves a subset of ports from a port group.

Step 2 Verify this configuration.

switch(config)# show hardware proxy layer-3 detail

Global Information:

F1 Modules: Count: 1 Slot: 8

M1 Modules: Count: 3 Slot: 1-3

Replication Rebalance Mode: Manual

Number of proxy layer-3 forwarders: 1

Number of proxy layer-3 replicators: 1

Forwarder Interfaces Status Reason

------------------------------------------------------------------------------

Eth2/1-12 up SUCCESS

Replicator Interfaces #Interface-Vlan Interface-Vlan

------------------------------------------------------------------------------

Eth2/1-24 0 <----------- full port group

switch(config)#

Note All ports in a port group are reserved for proxy routing.

Example: Excluding Ports From Proxy Routing

This example shows how to exclude some ports on a module from proxy routing.

Step 1 Exclude a subset of ports on a module.

switch(config)# hardware proxy layer-3 forwarding exclude interface ethernet 2/1-12 <---subset of port group

switch(config)# hardware proxy layer-3 replication exclude interface ethernet 2/1-12

Step 2 Verify this configuration.

switch(config)# show hardware proxy layer-3 detail

Global Information:

F1 Modules: Count: 1 Slot: 8

M1 Modules: Count: 3 Slot: 1-3

Replication Rebalance Mode: Manual

Number of proxy layer-3 forwarders: 12

Number of proxy layer-3 replicators: 7

Forwarder Interfaces Status Reason

------------------------------------------------------------------------------

Eth1/9, Eth1/11, Eth1/13, Eth1/15 up SUCCESS

Eth1/10, Eth1/12, Eth1/14, Eth1/16 up SUCCESS

Eth1/17, Eth1/19, Eth1/21, Eth1/23 up SUCCESS

Eth1/18, Eth1/20, Eth1/22, Eth1/24 up SUCCESS

Eth1/25, Eth1/27, Eth1/29, Eth1/31 up SUCCESS

Eth1/26, Eth1/28, Eth1/30, Eth1/32 up SUCCESS

Eth2/25-36 up SUCCESS

Eth2/37-48 up SUCCESS

Eth3/1-12 up SUCCESS

Eth3/13-24 up SUCCESS

Eth3/25-36 up SUCCESS

Eth3/37-48 up SUCCESS

Replicator Interfaces #Interface-Vlan Interface-Vlan

------------------------------------------------------------------------------

Eth1/1, Eth1/3, Eth1/5, Eth1/7, Eth1/9, 0

Eth1/11, Eth1/13, Eth1/15

Eth1/2, Eth1/4, Eth1/6, Eth1/8, Eth1/10, 0

Eth1/12, Eth1/14, Eth1/16

Eth1/17, Eth1/19, Eth1/21, Eth1/23, 0

Eth1/25, Eth1/27, Eth1/29, Eth1/31

Eth1/18, Eth1/20, Eth1/22, Eth1/24, 0

Eth1/26, Eth1/28, Eth1/30, Eth1/32

Eth2/25-48 0 <---- e 2/1-24 excluded

Eth3/1-24 0

Eth3/25-48 0

switch(config)#

Note All ports in the port group are excluded from proxy routing.

Additional References

For additional information related to implementing IP, see the following sections:

- Related Documents

- Standards

Related Documents

Related Topic

Document Title

IP CLI commands

Cisco Nexus 7000 Series NX-OS Unicast Routing Command Reference, Release 5.x

Standards

Standards

Title

No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.

—

Feature History for IP

Table 2-2 lists the release history for this feature.

Table 2-2 Feature History for IP

Feature Name

Releases

Feature Information

ACL filter for IP directed broadcasts

5.2(1)

Added support to filter IP directed broadcasts through an IP access list.

Glean Throttling

5.1(1)

Added support for IPv4 glean throttling.

ARP

4.1(4)

Added support to protect against an ARP broadcast storm.

IP

4.1(3)

Changed the platform ip verify command to the hardware ip verify command.

ARP

4.0(3)

Added support for gratuitous ARP. The following command was added:

- ip arp gratuitous { request | update }

IP

4.0(1)

Configuring OSPFv2

This chapter describes how to configure Open Shortest Path First version 2 (OSPFv2) for IPv4 networks on the Cisco NX-OS device.

This chapter includes the following sections:

- Information About OSPFv2

- Licensing Requirements for OSPFv2

- Prerequisites for OSPFv2

- Guidelines and Limitations for OSPFv2

- Default Settings

- Configuring Basic OSPFv2

- Configuring Advanced OSPFv2

- Verifying the OSPFv2 Configuration

- Monitoring OSPFv2

- Configuration Examples for OSPFv2

- Additional References

- Feature History for OSPFv2

Information About OSPFv2

OSPFv2 is an IETF link-state protocol (see the “Link-State Protocols” section) for IPv4 networks. An OSPFv2 router sends a special message, called a hello packet, out each OSPF-enabled interface to discover other OSPFv2 neighbor routers. Once a neighbor is discovered, the two routers compare information in the Hello packet to determine if the routers have compatible configurations. The neighbor routers try to establish adjacency, which means that the routers synchronize their link-state databases to ensure that they have identical OSPFv2 routing information. Adjacent routers share link-state advertisements (LSAs) that include information about the operational state of each link, the cost of the link, and any other neighbor information. The routers then flood these received LSAs out every OSPF-enabled interface so that all OSPFv2 routers eventually have identical link-state databases. When all OSPFv2 routers have identical link-state databases, the network is converged (see the “Convergence” section). Each router then uses Dijkstra’s Shortest Path First (SPF) algorithm to build its route table.

You can divide OSPFv2 networks into areas. Routers send most LSAs only within one area, which reduces the CPU and memory requirements for an OSPF-enabled router.

OSPFv2 supports IPv4, while OSPFv3 supports IPv6. For more information, see Chapter7, “Configuring OSPFv3”

Note OSPFv2 on Cisco NX-OS supports RFC 2328. This RFC introduced a different method to calculate route summary costs which is not compatible with the calculation used by RFC1583. RFC 2328 also introduced different selection criteria for AS-external paths. It is important_ to ensure that all routers support the same RFC. RFC. Use the rfc1583compatibility command if your network includes routers that are only compliant with RFC1583. The default supported RFC standard for OSPFv2 may be different for Cisco NX-OS and Cisco IOS. You must make adjustments to set the values identically. See the “OSPF RFC Compatibility Mode Example” section for more information.

This section includes the following topics:

- Hello Packet

- Neighbors

- Adjacency

- Designated Routers

- Areas

- Link-State Advertisements

- OSPFv2 and the Unicast RIB

- Authentication

- Advanced Features

Hello Packet

OSPFv2 routers periodically send Hello packets on every OSPF-enabled interface. The hello interval determines how frequently the router sends these Hello packets and is configured per interface. OSPFv2 uses Hello packets for the following tasks:

- Neighbor discovery

- Keepalives

- Bidirectional communications

- Designated router election (see the “Designated Routers” section)

The Hello packet contains information about the originating OSPFv2 interface and router, including the assigned OSPFv2 cost of the link, the hello interval, and optional capabilities of the originating router. An OSPFv2 interface that receives these Hello packets determines if the settings are compatible with the receiving interface settings. Compatible interfaces are considered neighbors and are added to the neighbor table (see the “Neighbors” section).

Hello packets also include a list of router IDs for the routers that the originating interface has communicated with. If the receiving interface sees its own router ID in this list, then bidirectional communication has been established between the two interfaces.

OSPFv2 uses Hello packets as a keepalive message to determine if a neighbor is still communicating. If a router does not receive a Hello packet by the configureddead interval (usually a multiple of the hello interval), then the neighbor is removed from the local neighbor table.

Neighbors

An OSPFv2 interface must have a compatible configuration with a remote interface before the two can be considered neighbors. The two OSPFv2 interfaces must match the following criteria:

- Hello interval

- Dead interval

- Area ID (see the “Areas” section)

- Authentication

- Optional capabilities

If there is a match, the following information is entered into the neighbor table:

- Neighbor ID—The router ID of the neighbor.

- Priority—Priority of the neighbor. The priority is used for designated router election (see the “Designated Routers” section).

- State—Indication of whether the neighbor has just been heard from, is in the process of setting up bidirectional communications, is sharing the link-state information, or has achieved full adjacency.

- Dead time—Indication of the time since the last Hello packet was received from this neighbor.

- IP Address—The IP address of the neighbor.

- Designated Router—Indication of whether the neighbor has been declared as the designated router or as the backup designated router (see the “Designated Routers” section).

- Local interface—The local interface that received the Hello packet for this neighbor.

Adjacency

Not all neighbors establish adjacency. Depending on the network type and designated router establishment, some neighbors become fully adjacent and share LSAs with all their neighbors, while other neighbors do not. For more information, see the “Designated Routers” section.

Adjacency is established using Database Description packets, Link State Request packets, and Link State Update packets in OSPF. The Database Description packet includes just the LSA headers from the link-state database of the neighbor (see the “Link-State Database” section). The local router compares these headers with its own link-state database and determines which LSAs are new or updated. The local router sends a Link State Request packet for each LSA that it needs new or updated information on. The neighbor responds with a Link State Update packet. This exchange continues until both routers have the same link-state information.

Designated Routers

Networks with multiple routers present a unique situation for OSPF. If every router floods the network with LSAs, the same link-state information is sent from multiple sources. Depending on the type of network, OSPFv2 might use a single router, the designated router (DR), to control the LSA floods and represent the network to the rest of the OSPFv2 area (see the “Areas” section). If the DR fails, OSPFv2 selects a backup designated router (BDR). If the DR fails, OSPFv2 uses the BDR.

Network types are as follows:

- Point-to-point—A network that exists only between two routers. All neighbors on a point-to-point network establish adjacency and there is no DR.

- Broadcast—A network with multiple routers that can communicate over a shared medium that allows broadcast traffic, such as Ethernet. OSPFv2 routers establish a DR and BDR that controls LSA flooding on the network. OSPFv2 uses the well-known IPv4 multicast addresses 224.0.0.5 and a MAC address of 0100.5300.0005 to communicate with neighbors.

The DR and BDR are selected based on the information in the Hello packet. When an interface sends a Hello packet, it sets the priority field and the DR and BDR field if it knows who the DR and BDR are. The routers follow an election procedure based on which routers declare themselves in the DR and BDR fields and the priority field in the Hello packet. As a final tie breaker, OSPFv2 chooses the highest router IDs as the DR and BDR.

All other routers establish adjacency with the DR and the BDR and use the IPv4 multicast address 224.0.0.6 to send LSA updates to the DR and BDR. Figure 6-1 shows this adjacency relationship between all routers and the DR.

DRs are based on a router interface. A router might be the DR for one network and not for another network on a different interface.

Figure 6-1 DR in Multi-Access Network

Areas

You can limit the CPU and memory requirements that OSPFv2 puts on the routers by dividing an OSPFv2 network into area s . An area is a logical division of routers and links within an OSPFv2 domain that creates separate subdomains. LSA flooding is contained within an area, and the link-state database is limited to links within the area. You can assign an area ID to the interfaces within the defined area. The Area ID is a 32-bit value that you can enter as a number or in dotted decimal notation, such as 10.2.3.1.

Cisco NX-OS always displays the area in dotted decimal notation.

If you define more than one area in an OSPFv2 network, you must also define the backbone area, which has the reserved area ID of 0. If you have more than one area, then one or more routers become area border router s (ABRs). An ABR connects to both the backbone area and at least one other defined area (see Figure 6-2).

Figure 6-2 OSPFv2 Areas

The ABR has a separate link-state database for each area to which it connects. The ABR sends Network Summary (type 3) LSAs (see the “Route Summarization” section) from one connected area to the backbone area. The backbone area sends summarized information about one area to another area. In Figure 6-2, Area 0 sends summarized information about Area 5 to Area 3.

OSPFv2 defines one other router type: the autonomous system boundary router (ASBR). This router connects an OSPFv2 area to another autonomous system. An autonomous system is a network controlled by a single technical administration entity. OSPFv2 can redistribute its routing information into another autonomous system or receive redistributed routes from another autonomous system. For more information, see the “Advanced Features” section.)

Link-State Advertisements

OSPFv2 uses link-state advertisements (LSAs) to build its routing table.

This section includes the following topics:

- LSA Types

- Link Cost

- Flooding and LSA Group Pacing

- Link-State Database

- Opaque LSAs

LSA Types

Table 6-1 shows the LSA types supported by Cisco NX-OS.

Table 6-1 LSA Types

Type

Name

Description

1

Router LSA

LSA sent by every router. This LSA includes the state and the cost of all links and a list of all OSPFv2 neighbors on the link. Router LSAs trigger an SPF recalculation. Router LSAs are flooded to local OSPFv2 area.

2

Network LSA

LSA sent by the DR. This LSA lists all routers in the multi-access network. Network LSAs trigger an SPF recalculation. See the “Designated Routers” section.

3

Network Summary LSA

LSA sent by the area border router to an external area for each destination in the local area. This LSA includes the link cost from the area border router to the local destination. See the “Areas” section.

4

ASBR Summary LSA

LSA sent by the area border router to an external area. This LSA advertises the link cost to the ASBR only. See the “Areas” section.

5

AS External LSA

LSA generated by the ASBR. This LSA includes the link cost to an external autonomous system destination. AS External LSAs are flooded throughout the autonomous system. See the “Areas” section.

7

NSSA External LSA

LSA generated by the ASBR within a not-so-stubby area (NSSA). This LSA includes the link cost to an external autonomous system destination. NSSA External LSAs are flooded only within the local NSSA. See the “Areas” section.

9–11

Opaque LSAs

LSA used to extend OSPF. See the “Opaque LSAs” section.

Link Cost

Each OSPFv2 interface is assigned a link cost. The cost is an arbitrary number. By default, Cisco NX-OS assigns a cost that is the configured reference bandwidth divided by the interface bandwidth. By default, the reference bandwidth is 40 Gb/s. The link cost is carried in the LSA updates for each link.

Flooding and LSA Group Pacing

When an OSPFv2 router receives an LSA, it forwards that LSA out every OSPF-enabled interface, flooding the OSPFv2 area with this information. This LSA flooding guarantees that all routers in the network have identical routing information. LSA flooding depends on the OSPFv2 area configuration (see the “Areas” section). The LSAs are flooded based on the link-state refresh time (every 30 minutes by default). Each LSA has its own link-state refresh time.

You can control the flooding rate of LSA updates in your network by using the LSA group pacing feature. LSA group pacing can reduce high CPU or buffer usage. This feature groups LSAs with similar link-state refresh times to allow OSPFv2 to pack multiple LSAs into an OSPFv2 Update message.

By default, LSAs with link-state refresh times within 10 seconds of each other are grouped together. You should lower this value for large link-state databases or raise it for smaller databases to optimize the OSPFv2 load on your network.

Link-State Database

Each router maintains a link-state database for the OSPFv2 network. This database contains all the collected LSAs, and includes information on all the routes through the network. OSPFv2 uses this information to calculate the bast path to each destination and populates the routing table with these best paths.

LSAs are removed from the link-state database if no LSA update has been received within a set interval, called the MaxAge. Routers flood a repeat of the LSA every 30 minutes to prevent accurate link-state information from being aged out. Cisco NX-OS supports the LSA grouping feature to prevent all LSAs from refreshing at the same time. For more information, see the “Flooding and LSA Group Pacing” section.

Opaque LSAs

Opaque LSAs allow you to extend OSPF functionality. Opaque LSAs consist of a standard LSA header followed by application-specific information. This information might be used by OSPFv2 or by other applications. OSPFv2 uses Opaque LSAs to support OSPFv2 Graceful Restart capability (see the “High Availability and Graceful Restart” section). Three Opaque LSA types are defined as follows:

- LSA type 9—Flooded to the local network.

- LSA type 10—Flooded to the local area.

- LSA type 11—Flooded to the local autonomous system.

OSPFv2 and the Unicast RIB

OSPFv2 runs the Dijkstra shortest path first algorithm on the link-state database. This algorithm selects the best path to each destination based on the sum of all the link costs for each link in the path. The resultant shortest path for each destination is then put in the OSPFv2 route table. When the OSPFv2 network is converged, this route table feeds into the unicast RIB. OSPFv2 communicates with the unicast RIB to do the following:

- Add or remove routes

- Handle route redistribution from other protocols

- Provide convergence updates to remove stale OSPFv2 routes and for stub router advertisements (see the “OSPFv2 Stub Router Advertisements” section)

OSPFv2 also runs a modified Dijkstra algorithm for fast recalculation for summary and external (type 3, 4, 5, and 7) LSA changes.

Authentication

You can configure authentication on OSPFv2 messages to prevent unauthorized or invalid routing updates in your network. Cisco NX-OS supports two authentication methods:

- Simple password authentication

- MD5 authentication digest

You can configure the OSPFv2 authentication for an OSPFv2 area or per interface.

Simple Password Authentication

Simple password authentication uses a simple clear-text password that is sent as part of the OSPFv2 message. The receiving OSPFv2 router must be configured with the same clear-text password to accept the OSPFv2 message as a valid route update. Because the password is in clear text, anyone who can watch traffic on the network can learn the password.

MD5 Authentication

You should use MD5 authentication to authenticate OSPFv2 messages. You configure a password that is shared at the local router and all remote OSPFv2 neighbors. For each OSPFv2 message, Cisco NX-OS creates an MD5 one-way message digest based on the message itself and the encrypted password. The interface sends this digest with the OSPFv2 message. The receiving OSPFv2 neighbor validates the digest using the same encrypted password. If the message has not changed, the digest calculation is identical and the OSPFv2 message is considered valid.

MD5 authentication includes a sequence number with each OSPFv2 message to ensure that no message is replayed in the network.

Advanced Features

Cisco NX-OS supports advanced OSPFv2 features that enhance the usability and scalability of OSPFv2 in the network. This section includes the following topics:

- Stub Area

- Not-So-Stubby Area

- Virtual Links

- Route Redistribution

- Route Summarization

- High Availability and Graceful Restart

- OSPFv2 Stub Router Advertisements

- Multiple OSPFv2 Instances

- SPF Optimization

- BFD

- Virtualization Support

Stub Area

You can limit the amount of external routing information that floods an area by making it a stub area. A stub area is an area that does not allow AS External (type 5) LSAs (see the “Link-State Advertisements” section). These LSAs are usually flooded throughout the local autonomous system to propagate external route information. Stub areas have the following requirements:

- All routers in the stub area are stub routers. See the “Stub Routing” section.

- No ASBR routers exist in the stub area.

- You cannot configure virtual links in the stub area.

Figure 6-3 shows an example of an OSPFv2 autonomous system where all routers in area 0.0.0.10 have to go through the ABR to reach external autonomous systems. Area 0.0.0.10 can be configured as a stub area.

Figure 6-3 Stub Area

Stub areas use a default route for all traffic that must go through the backbone area to the external autonomous system. The default route is 0.0.0.0 for IPv4.

Not-So-Stubby Area

A Not-so-Stubby Area (NSSA) is similar to a stub area, except that an NSSA allows you to import autonomous system external routes within an NSSA using redistribution. The NSSA ASBR redistributes these routes and generates NSSA External (type 7) LSAs that it floods throughout the NSSA. You can optionally configure the ABR that connects the NSSA to other areas to translate this NSSA External LSA to AS External (type 5) LSAs. The ABR then floods these AS External LSAs throughout the OSPFv2 autonomous system. Summarization and filtering are supported during the translation. See the “Link-State Advertisements” section for information about NSSA External LSAs.

You can, for example, use NSSA to simplify administration if you are connecting a central site using OSPFv2 to a remote site that is using a different routing protocol. Before NSSA, the connection between the corporate site border router and a remote router could not be run as an OSPFv2 stub area because routes for the remote site could not be redistributed into a stub area. With NSSA, you can extend OSPFv2 to cover the remote connection by defining the area between the corporate router and remote router as an NSSA (see the “Configuring NSSA” section).

The backbone Area 0 cannot be an NSSA.

Virtual Links

Virtual links allow you to connect an OSPFv2 area ABR to a backbone area ABR when a direct physical connection is not available. Figure 6-4 shows a virtual link that connects Area 3 to the backbone area through Area 5.

Figure 6-4 Virtual Links

You can also use virtual links to temporarily recover from a partitioned area, which occurs when a link within the area fails, isolating part of the area from reaching the designated ABR to the backbone area.

Route Redistribution

OSPFv2 can learn routes from other routing protocols by using route redistribution. See the “Route Redistribution” section. You configure OSPFv2 to assign a link cost for these redistributed routes or a default link cost for all redistributed routes.

Route redistribution uses route maps to control which external routes are redistributed. You must configure a route map with the redistribution to control which routes are passed into OSPFv2. A route map allows you to filter routes based on attributes such as the destination, origination protocol, route type, route tag, and so on. You can use route maps to modify parameters in the AS External (type 5) and NSSA External (type 7) LSAs before these external routes are advertised in the local OSPFv2 autonomous system. See “Configuring Route Policy Manager,” for information about configuring route maps.

Route Summarization

Because OSPFv2 shares all learned routes with every OSPF-enabled router, you might want to use route summarization to reduce the number of unique routes that are flooded to every OSPF-enabled router. Route summarization simplifies route tables by replacing more-specific addresses with an address that represents all the specific addresses. For example, you can replace 10.1.1.0/24, 10.1.2.0/24, and 10.1.3.0/24 with one summary address, 10.1.0.0/16.

Typically, you would summarize at the boundaries of area border routers (ABRs). Although you could configure summarization between any two areas, it is better to summarize in the direction of the backbone so that the backbone receives all the aggregate addresses and injects them, already summarized, into other areas. The two types of summarization are as follows:

- Inter-area route summarization

- External route summarization

You configure inter-area route summarization on ABRs, summarizing routes between areas in the autonomous system. To take advantage of summarization, you should assign network numbers in areas in a contiguous way to be able to lump these addresses into one range.

External route summarization is specific to external routes that are injected into OSPFv2 using route redistribution. You should make sure that external ranges that are being summarized are contiguous. Summarizing overlapping ranges from two different routers could cause packets to be sent to the wrong destination. Configure external route summarization on ASBRs that are redistributing routes into OSPF.

When you configure a summary address, Cisco NX-OS automatically configures a discard route for the summary address to prevent routing black holes and route loops.

High Availability and Graceful Restart

Cisco NX-OS provides a multilevel high-availability architecture. OSPFv2 supports stateful restart, which is also referred to as non-stop routing (NSR). If OSPFv2 experiences problems, it attempts to restart from its previous run-time state. The neighbors do not register any neighbor event in this case. If the first restart is not successful and another problem occurs, OSPFv2 attempts a graceful restart.

A graceful restart, or nonstop forwarding (NSF), allows OSPFv2 to remain in the data forwarding path through a process restart. When OSPFv2 needs to perform a graceful restart, it sends a link-local opaque (type 9) LSA, called a grace LSA (see the “Opaque LSAs” section). This restarting OSPFv2 platform is called NSF capable.

The grace LSA includes a grace period, which is a specified time that the neighbor OSPFv2 interfaces hold onto the LSAs from the restarting OSPFv2 interface. (Typically, OSPFv2 tears down the adjacency and discards all LSAs from a down or restarting OSPFv2 interface.) The participating neighbors, which are called NSF helpers, keep all LSAs that originate from the restarting OSPFv2 interface as if the interface was still adjacent.

When the restarting OSPFv2 interface is operational again, it rediscovers its neighbors, establishes adjacency, and starts sending its LSA updates again. At this point, the NSF helpers recognize that the graceful restart has finished.

Stateful restart is used in the following scenarios:

- First recovery attempt after the process experiences problems

- ISSU

- User-initiated switchover using the system switchover command

Graceful restart is used in the following scenarios:

- Second recovery attempt after the process experiences problems within a 4-minute interval

- Manual restart of the process using the restart ospf command

- Active supervisor removal

- Active supervisor reload using the reload module active-sup command

OSPFv2 Stub Router Advertisements

You can configure an OSPFv2 interface to act as a stub router using the OSPFv2 Stub Router Advertisements feature. Use this feature when you want to limit the OSPFv2 traffic through this router, such as when you want to introduce a new router to the network in a controlled manner or limit the load on a router that is already overloaded. You might also want to use this feature for various administrative or traffic engineering reasons.

OSPFv2 stub router advertisements do not remove the OSPFv2 router from the network topology, but they do prevent other OSPFv2 routers from using this router to route traffic to other parts of the network. Only the traffic that is destined for this router or directly connected to this router is sent.

OSPFv2 stub router advertisements mark all stub links (directly connected to the local router) to the cost of the local OSPFv2 interface. All remote links are marked with the maximum cost (0xFFFF).

Multiple OSPFv2 Instances

Cisco NX-OS supports multiple instances of the OSPFv2 protocol that run on the same node. You cannot configure multiple instances over the same interface. By default, every instance uses the same system router ID. You must manually configure the router ID for each instance if the instances are in the same OSPFv2 autonomous system.

SPF Optimization

Cisco NX-OS optimizes the SPF algorithm in the following ways:

- Partial SPF for Network (type 2) LSAs, Network Summary (type 3) LSAs, and AS External (type 5) LSAs—When there is a change on any of these LSAs, Cisco NX-OS performs a faster partial calculation rather than running the whole SPF calculation.

- SPF timers—You can configure different timers for controlling SPF calculations. These timers include exponential backoff for subsequent SPF calculations. The exponential backoff limits the CPU load of multiple SPF calculations.

BFD

This feature supports bidirectional forwarding detection (BFD). BFD is a detection protocol that provides fast forwarding-path failure detection times. BFD provides subsecond failure detection between two adjacent devices and can be less CPU-intensive than protocol hello messages because some of the BFD load can be distributed onto the data plane on supported modules. See the Cisco Nexus 7000 Series NX-OS Interfaces Configuration Guide, Release 5.x, for more information.

Virtualization Support

OSPFv2 supports virtual routing and forwarding (VRF) instances. VRFs exist within virtual device contexts (VDCs). By default, Cisco NX-OS places you in the default VDC and default VRF unless you specifically configure another VDC and VRF. You can have up to four instances of OSPFv2 in a VDC.

Each OSPFv2 instance can support multiple VRFs, up to the system limit. For more information, see the Cisco Nexus 7000 Series NX-OS Virtual Device Context Configuration Guide, Release 5.x, and see Chapter14, “Configuring Layer 3 Virtualization”

Licensing Requirements for OSPFv2

The following table shows the licensing requirements for this feature:

Product

License Requirement

Cisco NX-OS

OSPFv2 requires an Enterprise Services license. For a complete explanation of the Cisco NX-OS licensing scheme and how to obtain and apply licenses, see the Cisco NX-OS Licensing Guide.

Prerequisites for OSPFv2

OSPFv2 has the following prerequisites:

- You must be familiar with routing fundamentals to configure OSPF.

- You are logged on to the switch.

- You have configured at least one interface for IPv4 that can communicate with a remote OSPFv2 neighbor.

- You have installed the Enterprise Services license.

- You have completed the OSPFv2 network strategy and planning for your network. For example, you must decide whether multiple areas are required.

- You have enabled the OSPF feature (see the “Enabling OSPFv2” section).

- You have installed the Advanced Services license and entered the desired VDC (see the Cisco Nexus 7000 Series NX-OS Virtual Device Context Configuration Guide, Release 5.x) if you are configuring VDCs.

Guidelines and Limitations for OSPFv2

OSPFv2 has the following configuration guidelines and limitations:

- You can have up to four instances of OSPFv2 in a VDC.

- Cisco NX-OS displays areas in dotted decimal notation regardless of whether you enter the area in decimal or dotted decimal notation.

- All OSPFv2 routers must operate in the same RFC compatibility mode. OSPFv2 for Cisco NX-OS complies with RFC 2328. Use the rfc1583compatibility command in router configuration mode if your network includes routers that support only RFC 1583.

Note If you are familiar with the Cisco IOS CLI, be aware that the Cisco NX-OS commands for this feature might differ from the Cisco IOS commands that you would use.

Default Settings

Table 6-2 lists the default settings for OSPFv2 parameters.

Table 6-2 Default OSPFv2 Parameters

Parameters

Default

Hello interval

10 seconds

Dead interval

40 seconds

Graceful restart grace period

60 seconds

OSPFv2 feature

Disabled

Stub router advertisement announce time

600 seconds

Reference bandwidth for link cost calculation

40 Gb/s

LSA minimal arrival time

1000 milliseconds

LSA group pacing

10 seconds

SPF calculation initial delay time

200 milliseconds

SPF minimum hold time

5000 milliseconds

SPF calculation initial delay time

1000 milliseconds

Configuring Basic OSPFv2

Configure OSPFv2 after you have designed your OSPFv2 network.

This section includes the following topics:

- Enabling OSPFv2

- Creating an OSPFv2 Instance

- Configuring Optional Parameters on an OSPFv2 Instance

- Configuring Networks in OSPFv2

- Configuring Authentication for an Area

- Configuring Authentication for an Interface

Enabling OSPFv2

You must enable the OSPFv2 feature before you can configure OSPFv2.

BEFORE YOU BEGIN

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. feature ospf

3. (Optional) show feature

4. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

feature ospf

Example:

switch(config)# feature ospf

Enables the OSPFv2 feature.

Step 3

show feature

Example:

switch(config)# show feature

(Optional) Displays enabled and disabled features.

Step 4

copy running-config startup-config

Example:

switch(config)# copy running-config startup-config

(Optional) Saves this configuration change.

To disable the OSPFv2 feature and remove all associated configuration, use the no feature ospf command in configuration mode:

Command

Purpose

no feature ospf

Example:

switch(config)# no feature ospf

Disables the OSPFv2 feature and removes all associated configuration.

Creating an OSPFv2 Instance

The first step in configuring OSPFv2 is to create an OSPFv2 instance. You assign a unique instance tag for this OSPFv2 instance. The instance tag can be any string.

For more information about OSPFv2 instance parameters, see the “Configuring Advanced OSPFv2” section.

BEFORE YOU BEGIN

Ensure that you have enabled the OSPF feature (see the “Enabling OSPFv2” section).

Use the show ip ospf instance-tag command to verify that the instance tag is not in use.

OSPFv2 must be able to obtain a router identifier (for example, a configured loopback address) or you must configure the router ID option.

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. router ospf instance-tag

3. router-id ip-address

4. (Optional) show ip ospf instance-tag

5. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

router ospf instance-tag

Example:

switch(config)# router ospf 201

switch(config-router)#

Creates a new OSPFv2 instance with the configured instance tag.

Step 3

router-id ip-address

Example:

switch(config-router)# router-id 192.0.2.1

(Optional) Configures the OSPFv2 router ID. This IP address identifies this OSPFv2 instance and must exist on a configured interface in the system.

Step 4

show ip ospf instance-tag

Example:

switch(config-router)# show ip ospf 201

(Optional) Displays OSPF information.

Step 5

copy running-config startup-config

Example:

switch(config)# copy running-config startup-config

(Optional) Saves this configuration change.

To remove the OSPFv2 instance and all associated configuration, use the no router ospf command in configuration mode.

Command

Purpose

no router ospf instance-tag

Example:

switch(config)# no router ospf 201

Deletes the OSPF instance and the associated configuration.

Note This command does not remove the OSPF configuration in interface mode. You must manually remove any OSPFv2 commands configured in interface mode.

Configuring Optional Parameters on an OSPFv2 Instance

You can configure optional parameters for OSPF.

For more information about OSPFv2 instance parameters, see the “Configuring Advanced OSPFv2” section.

BEFORE YOU BEGIN

Ensure that you have enabled the OSPF feature (see the “Enabling OSPFv2” section).

OSPFv2 must be able to obtain a router identifier (for example, a configured loopback address) or you must configure the router ID option.

Ensure that you are in the correct VDC (or use the switchto vdc command).

DETAILED STEPS

You can configure the following optional parameters for OSPFv2 in router configuration mode:

Command

Purpose

distance number

Example:

switch(config-router)# distance 25

Configures the administrative distance for this OSPFv2 instance. The range is from 1 to 255. The default is 110.

log-adjacency-changes [detail]

Example:

switch(config-router)# log-adjacency-changes

Generates a system message whenever a neighbor changes state.

maximum-paths path-number

Example:

switch(config-router)# maximum-paths 4

Configures the maximum number of equal OSPFv2 paths to a destination in the route table. This command is used for load balancing. The range is from 1 to 16. The default is 8.

passive-interface default

Example:

switch(config-router)# passive-interface default

Suppresses routing updates on all interfaces. This command is overridden by the VRF or interface command mode configuration.

This example shows how to create an OSPFv2 instance:

switch# configure terminal

switch(config)# router ospf 201

switch(config-router)# copy running-config startup-config

Configuring Networks in OSPFv2

You can configure a network to OSPFv2 by associating it through the interface that the router uses to connect to that network (see the “Neighbors” section). You can add all networks to the default backbone area (Area 0), or you can create new areas using any decimal number or an IP address.

Note All areas must connect to the backbone area either directly or through a virtual link.

Note OSPF is not enabled on an interface until you configure a valid IP address for that interface.

BEFORE YOU BEGIN

Ensure that you have enabled the OSPF feature (see the “Enabling OSPFv2” section).

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. interface interface-type slot/port

3. ip address ip-prefix/length

4. ip router ospf instance-tag area area-id [secondaries none]

5. (Optional) show ip ospf instance-tag interface interface-type slot/port

6. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

interface interface-type slot/port

Example:

switch(config)# interface ethernet 1/2

switch(config-if)#

Enters interface configuration mode.

Step 3

ip address ip-prefix/length

Example:

switch(config-if)# ip address 192.0.2.1/16

Assigns an IP address and subnet mask to this interface.

Step 4

ip router ospf instance-tag area area-id [secondaries none]

Example:

switch(config-if)# ip router ospf 201 area 0.0.0.15

Adds the interface to the OSPFv2 instance and area.

Step 5

show ip ospf instance-tag interface interface-type slot/port

Example:

switch(config-if)# show ip ospf 201 interface ethernet 1/2

(Optional) Displays OSPF information.

Step 6

copy running-config startup-config

Example:

switch(config)# copy running-config startup-config

(Optional) Saves this configuration change.

You can configure the following optional parameters for OSPFv2 in interface configuration mode:

Command

Purpose

ip ospf cost number

Example:

switch(config-if)# ip ospf cost 25

Configures the OSPFv2 cost metric for this interface. The default is to calculate cost metric, based on the reference bandwidth and interface bandwidth. The range is from 1 to 65535.

ip ospf dead-interval seconds

Example:

switch(config-if)# ip ospf dead-interval 50

Configures the OSPFv2 dead interval, in seconds. The range is from 1 to 65535. The default is four times the hello interval, in seconds.

ip ospf hello-interval seconds

Example:

switch(config-if)# ip ospf hello-interval 25

Configures the OSPFv2 hello interval, in seconds. The range is from 1 to 65535. The default is 10 seconds.

ip ospf mtu-ignore

Example:

switch(config-if)# ip ospf mtu-ignore

Configures OSPFv2 to ignore any IP MTU mismatch with a neighbor. The default is to not establish adjacency if the neighbor MTU does not match the local interface MTU.

[default | no] ip ospf passive-interface

Example:

switch(config-if)# ip ospf passive-interface

Suppresses routing updates on the interface. This command overrides the router or VRF command mode configuration. The default option removes this interface mode command and reverts to the router or VRF configuration, if present.

ip ospf priority number

Example:

switch(config-if)# ip ospf priority 25

Configures the OSPFv2 priority, used to determine the DR for an area. The range is from 0 to 255. The default is 1. See the “Designated Routers” section.

ip ospf shutdown

Example:

switch(config-if)# ip ospf shutdown

Shuts down the OSPFv2 instance on this interface.

This example shows how to add a network area 0.0.0.10 in OSPFv2 instance 201:

switch# configure terminal

switch(config)# interface ethernet 1/2

switch(config-if)# ip address 192.0.2.1/16

switch(config-if)# ip router ospf 201 area 0.0.0.10

switch(config-if)# copy running-config startup-config

Use the show ip ospf interface command to verify the interface configuration. Use the show ip ospf neighbor command to see the neighbors for this interface.

Configuring Authentication for an Area

You can configure authentication for all networks in an area or for individual interfaces in the area. Interface authentication configuration overrides area authentication.

BEFORE YOU BEGIN

Ensure that you have enabled the OSPF feature (see the “Enabling OSPFv2” section).

Ensure that all neighbors on an interface share the same authentication configuration, including the shared authentication key.

Create the key chain for this authentication configuration. See the Cisco Nexus 7000 Series NX-OS Security Configuration Guide, Release 5.x.

Note For OSPFv2, the key identifier in the key key-id command supports values from 0 to 255 only.

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. router ospf instance-tag

3. area area-id authentication [message-digest]

4. interface interface-type slot/port

5. (Optional) ip ospf authentication-key [0 | 3] key

or

ip ospf message-digest-key key-id md5 [0 | 3] key

6. (Optional) show ip ospf instance-tag interface interface-type slot/port

7. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

router ospf instance-tag

Example:

switch(config)# router ospf 201

switch(config-router)#

Creates a new OSPFv2 instance with the configured instance tag.

Step 3

area area-id authentication [message-digest]

Example:

switch(config-router)# area 0.0.0.10 authentication

Configures the authentication mode for an area.

Step 4

interface interface-type slot/port

Example:

switch(config-router)# interface ethernet 1/2

switch(config-if)#

Enters interface configuration mode.

Step 5

ip ospf authentication-key [0 | 3] key

Example:

switch(config-if)# ip ospf authentication-key 0 mypass

(Optional) Configures simple password authentication for this interface. Use this command if the authentication is not set to key-chain or message-digest. 0 configures the password in clear text. 3 configures the password as 3DES encrypted.

ip ospf message-digest-key key-id md5 [0 | 3] key

Example:

switch(config-if)# ip ospf message-digest-key 21 md5 0 mypass

(Optional) Configures message digest authentication for this interface. Use this command if the authentication is set to message-digest. The key-id range is from 1 to 255. The MD5 option 0 configures the password in clear text and 3 configures the pass key as 3DES encrypted.

Step 6

show ip ospf instance-tag interface interface-type slot/port

Example:

switch(config-if)# show ip ospf 201 interface ethernet 1/2

(Optional) Displays OSPF information.

Step 7

copy running-config startup-config

Example:

switch(config)# copy running-config startup-config

(Optional) Saves this configuration change.

Configuring Authentication for an Interface

You can configure authentication for individual interfaces in the area. Interface authentication configuration overrides area authentication.

BEFORE YOU BEGIN

Ensure that you have enabled the OSPF feature (see the “Enabling OSPFv2” section).

Ensure that all neighbors on an interface share the same authentication configuration, including the shared authentication key.

Create the key chain for this authentication configuration. See the Cisco Nexus 7000 Series NX-OS Security Configuration Guide, Release 5.x.

Note For OSPFv2, the key identifier in the key key-id command supports values from 0 to 255 only.

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. interface interface-type slot/port

3. ip ospf authentication [message-digest]

4. (Optional) ip ospf authentication key-chain key-id

5. (Optional) ip ospf authentication-key [0 | 3 | 7] key

6. (Optional) ip ospf message-digest-key key-id md5 [0 | 3 | 7] key

7. (Optional) show ip ospf instance-tag interface interface-type slot/port

8. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

interface interface-type slot/port

Example:

switch(config)# interface ethernet 1/2

switch(config-if)#

Enters interface configuration mode.

Step 3

ip ospf authentication [message-digest]

Example:

switch(config-if)# ip ospf authentication

Enables interface authentication mode for OSPFv2 for either cleartext or message-digest type. Use this command to override area-based authentication for this interface. All neighbors must share this authentication type.

Step 4

ip ospf authentication key-chain key-id

Example:

switch(config-if)# ip ospf authentication key-chain Test1

(Optional) Configures interface authentication to use key chains for OSPFv2. See the Cisco Nexus 7000 Series NX-OS Security Configuration Guide, Release 5.x, for details on key chains.

Step 5

ip ospf authentication-key [0 | 3 | 7] key

Example:

switch(config-if)# ip ospf authentication-key 0 mypass

(Optional) Configures simple password authentication for this interface. Use this command if the authentication is not set to key-chain or message-digest.

The options are as follows:

- 0—Configures the password in clear text.

- 3—Configures the pass key as 3DES encrypted.

- 7—Configures the key as Cisco type 7 encrypted.

Step 6

ip ospf message-digest-key key-id md5 [0 | 3 | 7] key

Example:

switch(config-if)# ip ospf message-digest-key 21 md5 0 mypass

(Optional) Configures message digest authentication for this interface. Use this command if the authentication is set to message-digest.The key-id range is from 1 to 255. The MD5 options are as follows:

- 0—Configures the password in clear text.

- 3—Configures the pass key as 3DES encrypted.

- 7—Configures the key as Cisco type 7 encrypted.

Step 7

show ip ospf instance-tag interface interface-type slot/port

Example:

switch(config-if)# show router ospf 201 interface ethernet 1/2

(Optional) Displays OSPF information.

Step 8

copy running-config startup-config

Example:

switch(config)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to set an interface for simple, unencrypted passwords and set the password for Ethernet interface 1/2:

switch# configure terminal

switch(config)# router ospf 201

switch(config-router)# exit

switch(config)# interface ethernet 1/2

switch(config-if)# ip router ospf 201 area 0.0.0.10

switch(config-if)# ip ospf authentication

switch(config-if)# ip ospf authentication-key 0 mypass

switch(config-if)# copy running-config startup-config

Configuring Advanced OSPFv2

Configure OSPFv2 after you have designed your OSPFv2 network.

This section includes the following topics:

- Configuring Filter Lists for Border Routers

- Configuring Stub Areas

- Configuring a Totally Stubby Area

- Configuring NSSA

- Configuring Virtual Links

- Configuring Redistribution

- Limiting the Number of Redistributed Routes

- Configuring Route Summarization

- Configuring Stub Route Advertisements

- Modifying the Default Timers

- Configuring Graceful Restart

- Restarting an OSPFv2 Instance

Configuring Filter Lists for Border Routers

You can separate your OSPFv2 domain into a series of areas that contain related networks. All areas must connect to the backbone area through an area border router (ABR). OSPFv2 domains can connect to external domains through an autonomous system border router (ASBR). See the “Areas” section.

ABRs have the following optional configuration parameters:

- Area range—Configures route summarization between areas. See the “Configuring Route Summarization” section.

- Filter list—Filters the Network Summary (type 3) LSAs that are allowed in from an external area.

ASBRs also support filter lists.

BEFORE YOU BEGIN

Ensure that you have enabled the OSPF feature (see the “Enabling OSPFv2” section).

Create the route map that the filter list uses to filter IP prefixes in incoming or outgoing Network Summary (type 3) LSAs. See Chapter16, “Configuring Route Policy Manager”

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. router ospf instance-tag

3. area area-id filter-list route-map map-name {in | out}

4. (Optional) show ip ospf policy statistics area id filter-list {in | out}

5. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

router ospf instance-tag

Example:

switch(config)# router ospf 201

switch(config-router)#

Creates a new OSPFv2 instance with the configured instance tag.

Step 3

area area-id filter-list route-map map-name {in | out}

Example:

switch(config-router)# area 0.0.0.10 filter-list route-map FilterLSAs in

Filters incoming or outgoing Network Summary (type 3) LSAs on an ABR.

Step 4

show ip ospf policy statistics area id filter-list {in | out}

Example:

switch(config-if)# show ip ospf policy statistics area 0.0.0.10 filter-list in

(Optional) Displays OSPF policy information.

Step 5

copy running-config startup-config

Example:

switch(config)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to configure a filter list in area 0.0.0.10:

switch# configure terminal

switch(config)# router ospf 201

switch(config-router)# area 0.0.0.10 filter-list route-map FilterLSAs in

switch(config-router)# copy running-config startup-config

Configuring Stub Areas

You can configure a stub area for part of an OSPFv2 domain where external traffic is not necessary. Stub areas block AS External (type 5) LSAs and limit unnecessary routing to and from selected networks. See the “Stub Area” section. You can optionally block all summary routes from going into the stub area.

BEFORE YOU BEGIN

Ensure that you have enabled the OSPF feature (see the “Enabling OSPFv2” section).

Ensure that there are no virtual links or ASBRs in the proposed stub area.

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. router ospf instance-tag

3. area area-id stub

4. (Optional) area area-id default-cost cost

5. (Optional) show ip ospf instance-tag

6. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

router ospf instance-tag

Example:

switch(config)# router ospf 201

switch(config-router)#

Creates a new OSPFv2 instance with the configured instance tag.

Step 3

area area-id stub

Example:

switch(config-router)# area 0.0.0.10 stub

Creates this area as a stub area.

Step 4

area area-id default-cost cost

Example:

switch(config-router)# area 0.0.0.10 default-cost 25

(Optional) Sets the cost metric for the default summary route sent into this stub area. The range is from 0 to 16777215. The default is 1.

Step 5

show ip ospf instance-tag

Example:

switch(config-if)# show ip ospf 201

(Optional) Displays OSPF information.

Step 6

copy running-config startup-config

Example:

switch(config)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to create a stub area:

switch# configure terminal

switch(config)# router ospf 201

switch(config-router)# area 0.0.0.10 stub

switch(config-router)# copy running-config startup-config

Configuring a Totally Stubby Area

You can create a totally stubby area and prevent all summary route updates from going into the stub area.

To create a totally stubby area, use the following command in router configuration mode:

Command

Purpose

area area-id stub no-summary

Example:

switch(config-router)# area 20 stub no-summary

Creates this area as a totally stubby area.

Configuring NSSA

You can configure an NSSA for part of an OSPFv2 domain where limited external traffic is required. For information about NSSAs, see the “Not-So-Stubby Area” section. You can optionally translate this external traffic to an AS External (type 5) LSA and flood the OSPFv2 domain with this routing information. An NSSA can be configured with the following optional parameters:

- No redistribution— Redistributed routes bypass the NSSA and are redistributed to other areas in the OSPFv2 autonomous system. Use this option when the NSSA ASBR is also an ABR.

- Default information originate—Generates an NSSA External (type 7) LSA for a default route to the external autonomous system. Use this option on an NSSA ASBR if the ASBR contains the default route in the routing table. This option can be used on an NSSA ABR whether or not the ABR contains the default route in the routing table.

- Route map—Filters the external routes so that only those routes that you want are flooded throughout the NSSA and other areas.

- Translate—Translates NSSA External LSAs to AS External LSAs for areas outside the NSSA. Use this command on an NSSA ABR to flood the redistributed routes throughout the OSPFv2 autonomous system. You can optionally suppress the forwarding address in these AS External LSAs. If you choose this option, the forwarding address is set to 0.0.0.0.

- No summary—Blocks all summary routes from flooding the NSSA. Use this option on the NSSA ABR.

BEFORE YOU BEGIN

Ensure that you have enabled the OSPF feature (see the “Enabling OSPFv2” section).

Ensure that there are no virtual links in the proposed NSSA and that it is not the backbone area.

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. router ospf instance-tag

3. area area-id nssa [no-redistribution] [default-information-originate [route-map map-name]] [no-summary] [translate type7 {always | never} [suppress-fa]]

4. (Optional) area area-id default-cost cost

5. (Optional) show ip ospf instance-tag

6. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

router ospf instance-tag

Example:

switch(config)# router ospf 201

switch(config-router)#

Creates a new OSPFv2 instance with the configured instance tag.

Step 3

area area-id nssa [no-redistribution] [default-information-originate

[route-map map-name]] [no-summary] [translate type7 {always | never} [suppress-fa]]

Example:

switch(config-router)# area 0.0.0.10 nssa

Creates this area as an NSSA.

Step 4

area area-id default-cost cost

Example:

switch(config-router)# area 0.0.0.10 default-cost 25

(Optional) Sets the cost metric for the default summary route sent into this NSSA.

Step 5

show ip ospf instance-tag

Example:

switch(config-if)# show ip ospf 201

(Optional) Displays OSPF information.

Step 6

copy running-config startup-config

Example:

switch(config)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to create an NSSA that blocks all summary route updates:

switch# configure terminal

switch(config)# router ospf 201

switch(config-router)# area 0.0.0.10 nssa no-summary

switch(config-router)# copy running-config startup-config

This example shows how to create an NSSA that generates a default route:

switch# configure terminal

switch(config)# router ospf 201

switch(config-router)# area 0.0.0.10 nssa default-info-originate

switch(config-router)# copy running-config startup-config

This example shows how to create an NSSA that filters external routes and blocks all summary route updates:

switch# configure terminal

switch(config)# router ospf 201

switch(config-router)# area 0.0.0.10 nssa route-map ExternalFilter no-summary

switch(config-router)# copy running-config startup-config

This example shows how to create an NSSA that always translates NSSA External (type 5) LSAs to AS External (type 7) LSAs:

switch# configure terminal

switch(config)# router ospf 201

switch(config-router)# area 0.0.0.10 nssa translate type 7 always

switch(config-router)# copy running-config startup-config

Configuring Virtual Links

A virtual link connects an isolated area to the backbone area through an intermediate area. See the “Virtual Links” section. You can configure the following optional parameters for a virtual link:

- Authentication—Sets a simple password or MD5 message digest authentication and associated keys.

- Dead interval—Sets the time that a neighbor waits for a Hello packet before declaring the local router as dead and tearing down adjacencies.

- Hello interval—Sets the time between successive Hello packets.

- Retransmit interval—Sets the estimated time between successive LSAs.

- Transmit delay—Sets the estimated time to transmit an LSA to a neighbor.

Note You must configure the virtual link on both routers involved before the link becomes active.

You cannot add a virtual link to a stub area.

BEFORE YOU BEGIN

Ensure that you have enabled OSPF (see the “Enabling OSPFv2” section).

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. router ospf instance-tag

3. area area-id virtual-link router-id

4. (Optional) show ip ospf virtual-link [brief]

5. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

router ospf instance-tag

Example:

switch(config)# router ospf 201

switch(config-router)#

Creates a new OSPFv2 instance with the configured instance tag.

Step 3

area area-id virtual-link router-id

Example:

switch(config-router)# area 0.0.0.10 virtual-link 10.1.2.3

switch(config-router-vlink)#

Creates one end of a virtual link to a remote router. You must create the virtual link on that remote router to complete the link.

Step 4

show ip ospf virtual-link [brief]

Example:

switch(config-router-vlink)# show ip ospf virtual-link

(Optional) Displays OSPF virtual link information.

Step 5

copy running-config startup-config

Example:

switch(config-router-vlink)# copy running-config startup-config

(Optional) Saves this configuration change.

You can configure the following optional commands in virtual link configuration mode:

Command

Purpose

authentication [key-chain key-id | message-digest | null]

Example:

switch(config-router-vlink)# authentication message-digest

(Optional) Overrides area-based authentication for this virtual link.

authentication-key [0 | 3] key

Example:

switch(config-router-vlink)# authentication-key 0 mypass

(Optional) Configures a simple password for this virtual link. Use this command if the authentication is not set to key-chain or message-digest. 0 configures the password in clear text. 3 configures the password as 3DES encrypted.

dead-interval seconds

Example:

switch(config-router-vlink)# dead-interval 50

(Optional) Configures the OSPFv2 dead interval, in seconds. The range is from 1 to 65535. The default is four times the hello interval, in seconds.

hello-interval seconds

Example:

switch(config-router-vlink)# hello-interval 25

(Optional) Configures the OSPFv2 hello interval, in seconds. The range is from 1 to 65535. The default is 10 seconds.

message-digest-key key-id md5 [0 | 3] key

Example:

switch(config-router-vlink)#

message-digest-key 21 md5 0 mypass

(Optional) Configures message digest authentication for this virtual link. Use this command if the authentication is set to message-digest. 0 configures the password in cleartext. 3 configures the pass key as 3DES encrypted.

retransmit-interval seconds

Example:

switch(config-router-vlink)# retransmit-interval 50

(Optional) Configures the OSPFv2 retransmit interval, in seconds. The range is from 1 to 65535. The default is 5.

transmit-delay seconds

Example:

switch(config-router-vlink)# transmit-delay 2

(Optional) Configures the OSPFv2 transmit-delay, in seconds. The range is from 1 to 450. The default is 1.

This example shows how to create a simple virtual link between two ABRs.

The configuration for ABR 1 (router ID 27.0.0.55) is as follows:

switch# configure terminal

switch(config)# router ospf 201

switch(config-router)# area 0.0.0.10 virtual-link 10.1.2.3

switch(config-router)# copy running-config startup-config

The configuration for ABR 2 (Router ID 10.1.2.3) is as follows:

switch# configure terminal

switch(config)# router ospf 101

switch(config-router)# area 0.0.0.10 virtual-link 27.0.0.55

switch(config-router)# copy running-config startup-config

Configuring Redistribution

You can redistribute routes learned from other routing protocols into an OSPFv2 autonomous system through the ASBR.

You can configure the following optional parameters for route redistribution in OSPF:

- Default information originate—Generates an AS External (type 5) LSA for a default route to the external autonomous system.

Note Default information originate ignores match statements in the optional route map.

- Default metric—Sets all redistributed routes to the same cost metric.

Note If you redistribute static routes, Cisco NX-OS also redistributes the default static route.

BEFORE YOU BEGIN

Ensure that you have enabled OSPF (see the “Enabling OSPFv2” section).

Create the necessary route maps used for redistribution.

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. router ospf instance-tag

3. redistribute {bgp id | direct | eigrp id | isis id | ospf id | rip id | static} route-map map-name

4. default-information originate [always] [route-map map-name]

5. default-metric cost

6. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

router ospf instance-tag

Example:

switch(config)# router ospf 201

switch(config-router)#

Creates a new OSPFv2 instance with the configured instance tag.

Step 3

redistribute {bgp id | direct | eigrp id | isis id | ospf id | rip id | static} route-map map-name

Example:

switch(config-router)# redistribute bgp route-map FilterExternalBGP

Redistributes the selected protocol into OSPF through the configured route map.

Note If you redistribute static routes, Cisco NX-OS also redistributes the default static route.

Step 4

default-information originate [always] [route-map map-name]

Example:

switch(config-router)# default-information-originate route-map DefaultRouteFilter

Creates a default route into this OSPF domain if the default route exists in the RIB. Use the following optional keywords:

- always —Always generate the default route of 0.0.0. even if the route does not exist in the RIB.

- route-map —Generate the default route if the route map returns true.

statements in the route map.

Step 5

default-metric cost

Example:

switch(config-router)# default-metric 25

Sets the cost metric for the redistributed routes. This command does not apply to directly connected routes. Use a route map to set the default metric for directly connected routes.

Step 6

copy running-config startup-config

Example:

switch(config-router)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to redistribute the Border Gateway Protocol (BGP) into OSPF:

switch# configure terminal

switch(config)# router ospf 201

switch(config-router)# redistribute bgp route-map FilterExternalBGP

switch(config-router)# copy running-config startup-config

Limiting the Number of Redistributed Routes

Route redistribution can add many routes to the OSPFv2 route table. You can configure a maximum limit to the number of routes accepted from external protocols. OSPFv2 provides the following options to configure redistributed route limits:

- Fixed limit—Logs a message when OSPFv2 reaches the configured maximum. OSPFv2 does not accept any more redistributed routes. You can optionally configure a threshold percentage of the maximum where OSPFv2 logs a warning when that threshold is passed.

- Warning only—Logs a warning only when OSPFv2 reaches the maximum. OSPFv2 continues to accept redistributed routes.

- Withdraw—Starts the timeout period when OSPFv2 reaches the maximum. After the timeout period, OSPFv2 requests all redistributed routes if the current number of redistributed routes is less than the maximum limit. If the current number of redistributed routes is at the maximum limit, OSPFv2 withdraws all redistributed routes. You must clear this condition before OSPFv2 accepts more redistributed routes.

- You can optionally configure the timeout period.

BEFORE YOU BEGIN

Ensure that you have enabled OSPF (see the “Enabling OSPFv2” section).

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. router ospf instance-tag

3. redistribute {bgp id | direct | eigrp id | isis id | ospf id | rip id | static} route-map map-name

4. redistribute maximum-prefix max [threshold] [warning-only | withdraw [num-retries timeout]]

5. (Optional) show running-config ospf

6. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

router ospf instance-tag

Example:

switch(config)# router ospf 201

switch(config-router)#

Creates a new OSPFv2 instance with the configured instance tag.

Step 3

redistribute {bgp id | direct | eigrp id | isis id | ospf id | rip id | static} route-map map-name

Example:

switch(config-router)# redistribute bgp route-map FilterExternalBGP

Redistributes the selected protocol into OSPF through the configured route map.

Step 4

redistribute maximum-prefix max [threshold] [warning-only | withdraw [num-retries timeout]]

Example:

switch(config-router)# redistribute maximum-prefix 1000 75 warning-only

Specifies a maximum number of prefixes that OSPFv2 distributes. The range is from 0 to 65536. Optionally specifies the following:

- threshold —Percent of maximum prefixes that trigger a warning message.

- warning-only —Logs an warning message when the maximum number of prefixes is exceeded.

- withdraw —Withdraws all redistributed routes. Optionally tries to retrieve the redistributed routes. The num-retries range is from 1 to 12. The timeout is 60 to 600 seconds. The default is 300 seconds. Use the clear ip ospf redistribution command if all routes are withdrawn.

Step 5

show running-config ospf

Example:

switch(config-router)# show running-config ospf

(Optional) Displays the OSPFv2 configuration.

Step 6

copy running-config startup-config

Example:

switch(config-router)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to limit the number of redistributed routes into OSPF:

switch# configure terminal

switch(config)# router ospf 201

switch(config-router)# redistribute bgp route-map FilterExternalBGP

switch(config-router)# redistribute maximum-prefix 1000 75

Configuring Route Summarization

You can configure route summarization for inter-area routes by configuring an address range that is summarized. You can also configure route summarization for external, redistributed routes by configuring a summary address for those routes on an ASBR. For more information, see the “Route Summarization” section.

BEFORE YOU BEGIN

Ensure that you have enabled OSPF (see the “Enabling OSPFv2” section).

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. router ospf instance-tag

3. area area-id range ip-prefix/length [no-advertise] [cost cost]

or

4. summary-address ip-prefix/length [no-advertise | tag tag-id]

5. (Optional) show ip ospf summary-address

6. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

router ospf instance-tag

Example:

switch(config)# router ospf 201

switch(config-router)#

Creates a new OSPFv2 instance with the configured instance tag.

Step 3

area area-id range ip-prefix/length [no-advertise] [cost cost]

Example:

switch(config-router)# area 0.0.0.10 range 10.3.0.0/16

Creates a summary address on an ABR for a range of addresses and optionally does not advertise this summary address in a Network Summary (type 3) LSA. The cost range is from 0 to 16777215.

Step 4

summary-address ip-prefix/length [no-advertise | tag tag]

Example:

switch(config-router)# summary-address 10.5.0.0/16 tag 2

Creates a summary address on an ASBR for a range of addresses and optionally assigns a tag for this summary address that can be used for redistribution with route maps.

Step 5

show ip ospf summary-address

Example:

switch(config-router)# show ip ospf summary-address

(Optional) Displays information about OSPF summary addresses.

Step 6

copy running-config startup-config

Example:

switch(config-router)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to create summary addresses between areas on an ABR:

switch# configure terminal

switch(config)# router ospf 201

switch(config-router)# area 0.0.0.10 range 10.3.0.0/16

switch(config-router)# copy running-config startup-config

This example shows how to create summary addresses on an ASBR:

switch# configure terminal

switch(config)# router ospf 201

switch(config-router)# summary-address 10.5.0.0/16

switch(config-router)# copy running-config startup-config

Configuring Stub Route Advertisements

Use stub route advertisements when you want to limit the OSPFv2 traffic through this router for a short time. For more information, see the “OSPFv2 Stub Router Advertisements” section.

Stub route advertisements can be configured with the following optional parameters:

- On startup—Sends stub route advertisements for the specified announce time.

- Wait for BGP—Sends stub router advertisements until BGP converges.

Note You should not save the running configuration of a router when it is configured for a graceful shutdown because the router continues to advertise a maximum metric after it is reloaded.

BEFORE YOU BEGIN

Ensure that you have enabled OSPF (see the “Enabling OSPFv2” section).

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. router ospf instance-tag

3. max-metric router-lsa [on-startup [announce-time] [wait-for bgp tag]]

4. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

router ospf instance-tag

Example:

switch(config)# router ospf 201

switch(config-router)#

Creates a new OSPFv2 instance with the configured instance tag.

Step 3

max-metric router-lsa [on-startup [announce-time] [wait-for bgp tag]]

Example:

switch(config-router)# max-metric router-lsa

Configures OSPFv2 stub route advertisements.

Step 4

copy running-config startup-config

Example:

switch(config-router)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to enable the stub router advertisements on startup for the default 600 seconds:

switch# configure terminal

switch(config)# router ospf 201

switch(config-router)# max-metric router-lsa on-startup

switch(config-router)# copy running-config startup-config

Modifying the Default Timers

OSPFv2 includes a number of timers that control the behavior of protocol messages and shortest path first (SPF) calculations. OSPFv2 includes the following optional timer parameters:

- LSA arrival time—Sets the minimum interval allowed between LSAs that arrive from a neighbor. LSAs that arrive faster than this time are dropped.

- Pacing LSAs—Sets the interval at which LSAs are collected into a group and refreshed, checksummed, or aged. This timer controls how frequently LSA updates occur and optimizes how many are sent in an LSA update message (see the “Flooding and LSA Group Pacing” section).

- Throttle LSAs—Sets the rate limits for generating LSAs. This timer controls how frequently LSAs are generated after a topology change occurs.

- Throttle SPF calculation—Controls how frequently the SPF calculation is run.

At the interface level, you can also control the following timers:

- Retransmit interval—Sets the estimated time between successive LSAs.

- Transmit delay—Sets the estimated time to transmit an LSA to a neighbor.

See the “Configuring Networks in OSPFv2” section for information about the hello interval and dead timer.

BEFORE YOU BEGIN

Ensure that you have enabled OSPF (see the “Enabling OSPFv2” section).

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. router ospf instance-tag

3. timers lsa-arrival msec

4. timers lsa-group-pacing seconds

5. timers throttle lsa start-time hold-interval max-time

6. timers throttle spf delay-time hold-time

7. interface type slot/port

8. ip ospf hello-interval seconds

9. ip ospf dead-interval seconds

10. ip ospf retransmit-interval seconds

11. ip ospf transmit-delay seconds

12. (Optional) show ip ospf

13. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

router ospf instance-tag

Example:

switch(config)# router ospf 201

switch(config-router)#

Creates a new OSPFv2 instance with the configured instance tag.

Step 3

timers lsa-arrival msec

Example:

switch(config-router)# timers lsa-arrival 2000

Sets the LSA arrival time in milliseconds. The range is from 10 to 600000. The default is 1000 milliseconds.

Step 4

timers lsa-group-pacing seconds

Example:

switch(config-router)# timers lsa-group-pacing 200

Sets the interval in seconds for grouping LSAs. The range is from 1 to 1800. The default is 10 seconds.

Step 5

timers throttle lsa start-time hold-interval max-time

Example:

switch(config-router)# timers throttle lsa 3000

Sets the rate limit in milliseconds for generating LSAs with the following timers:

start-time—The range is from 0 to 5000 milliseconds. The default value is 0 milliseconds.

hold-interval—The range is from 50 to 30,000 milliseconds. The default value is 5000 milliseconds.

max-time—The range is from 50 to 30,000 milliseconds. The default value is 5000 milliseconds.

Step 6

timers throttle spf delay-time hold-time max-wait

Example:

switch(config-router)# timers throttle spf 3000 2000 4000

Sets the SPF best path schedule initial delay time and the minimum hold time in seconds between SPF best path calculations. The range is from 1 to 600000. The default is no delay time and a 5000-millisecond hold time.

Step 7

interface type slot/port

Example:

switch(config)# interface ethernet 1/2

switch(config-if)#

Enters interface configuration mode.

Step 8

ip ospf hello-interval seconds

Example:

switch(config-if)# ip ospf hello-interval 30

Sets the hello interval for this interface. The range is from 1 to 65535. The default is 10.

Step 9

ip ospf dead-interval seconds

Example:

switch(config-if)# ip ospf dead-interval 30

Sets the dead interval for this interface. The range is from 1 to 65535.

Step 10

ip ospf retransmit-interval seconds

Example:

switch(config-if)# ip ospf retransmit-interval 30

Sets the estimated time in seconds between LSAs transmitted from this interface. The range is from 1 to 65535. The default is 5.

Step 11

ip ospf transmit-delay seconds

Example:

switch(config-if)# ip ospf transmit-delay 600

switch(config-if)#

Sets the estimated time in seconds to transmit an LSA to a neighbor. The range is from 1 to 450. The default is 1.

Step 12

show ip ospf

Example:

switch(config-if)# show ip ospf

(Optional) Displays information about OSPF.

Step 13

copy running-config startup-config

Example:

switch(config-if)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to control LSA flooding with the lsa-group-pacing option:

switch# configure terminal

switch(config)# router ospf 201

switch(config-router)# timers lsa-group-pacing 300

switch(config-router)# copy running-config startup-config

Configuring Graceful Restart

Graceful restart is enabled by default. You can configure the following optional parameters for graceful restart in an OSPFv2 instance:

- Grace period—Configures how long neighbors should wait after a graceful restart has started before tearing down adjacencies.

- Helper mode disabled—Disables helper mode on the local OSPFv2 instance. OSPFv2 does not participate in the graceful restart of a neighbor.

- Planned graceful restart only—Configures OSPFv2 to support graceful restart only in the event of a planned restart.

BEFORE YOU BEGIN

Ensure that you have enabled OSPF (see the “Enabling OSPFv2” section).

Ensure that all neighbors are configured for graceful restart with matching optional parameters set.

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. router ospf instance-tag

3. graceful-restart

4. (Optional) graceful-restart grace-period seconds

5. (Optional) graceful-restart helper-disable

6. (Optional) graceful-restart planned-only

7. (Optional) show ip ospf instance-tag

8. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

router ospf instance-tag

Example:

switch(config)# router ospf 201

switch(config-router)#

Creates a new OSPFv2 instance with the configured instance tag.

Step 3

graceful-restart

Example:

switch(config-router)# graceful-restart

Enables a graceful restart. A graceful restart is enabled by default.

Step 4

graceful-restart grace-period seconds

Example:

switch(config-router)# graceful-restart grace-period 120

(Optional) Sets the grace period, in seconds. The range is from 5 to 1800. The default is 60 seconds.

Step 5

graceful-restart helper-disable

Example:

switch(config-router)# graceful-restart helper-disable

(Optional) Disables helper mode. This feature is enabled by default.

Step 6

graceful-restart planned-only

Example:

switch(config-router)# graceful-restart planned-only

(Optional) Configures a graceful restart for planned restarts only.

Step 7

show ip ospf instance-tag

Example:

switch(config-if)# show ip ospf 201

(Optional) Displays OSPF information.

Step 8

copy running-config startup-config

Example:

switch(config)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to enable a graceful restart if it has been disabled and set the grace period to 120 seconds:

switch# configure terminal

switch(config)# router ospf 201

switch(config-router)# graceful-restart

switch(config-router)# graceful-restart grace-period 120

switch(config-router)# copy running-config startup-config

Restarting an OSPFv2 Instance

You can restart an OSPv2 instance. This action clears all neighbors for the instance.

To restart an OSPFv2 instance and remove all associated neighbors, use the following command:

Command

Purpose

restart ospf instance-tag

Example:

switch(config)# restart ospf 201

Restarts the OSPFv2 instance and removes all neighbors.

Configuring OSPFv2 with Virtualization

You can configure multiple OSPFv2 instances in each VDC. You can also create multiple VRFs within each VDC and use the same or multiple OSPFv2 instances in each VRF. You assign an OSPFv2 interface to a VRF.

Note Configure all other parameters for an interface after you configure the VRF for an interface. Configuring a VRF for an interface deletes all the configuration for that interface.

BEFORE YOU BEGIN

Create the VDCs.

Ensure that you have enabled OSPF (see the “Enabling OSPFv2” section).

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. vrf context vrf_name

3. router ospf instance-tag

4. vrf vrf-name

5. (Optional) maximum-paths paths

6. interface interface-type slot/port

7. vrf member vrf-name

8. ip-address ip-prefix/length

9. router ospf instance-tag area area-id

10. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

vrf context vrf-name

Example:

switch(config)# vrf context RemoteOfficeVRF

switch(config-vrf)#

Creates a new VRF and enters VRF configuration mode.

Step 3

router ospf instance-tag

Example:

switch(config-vrf)# router ospf 201

switch(config-router)#

Creates a new OSPFv2 instance with the configured instance tag.

Step 4

vrf vrf-name

Example:

switch(config-router)# vrf RemoteOfficeVRF

switch(config-router-vrf)#

Enters VRF configuration mode.

Step 5

maximum-paths paths

Example:

switch(config-router-vrf)# maximum-paths 4

(Optional) Configures the maximum number of equal OSPFv2 paths to a destination in the route table for this VRF. This feature is used for load balancing.

Step 6

interface interface-type slot/port

Example:

switch(config-router-vrf)# interface ethernet 1/2

switch(config-if)#

Enters interface configuration mode.

Step 7

vrf member vrf-name

Example:

switch(config-if)# vrf member RemoteOfficeVRF

Adds this interface to a VRF.

Step 8

ip address ip-prefix/length

Example:

switch(config-if)# ip address 192.0.2.1/16

Configures an IP address for this interface. You must do this step after you assign this interface to a VRF.

Step 9

ip router ospf instance-tag area area-id

Example:

switch(config-if)# ip router ospf 201 area 0

Assigns this interface to the OSPFv2 instance and area configured.

Step 10

copy running-config startup-config

Example:

switch(config)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to create a VRF and add an interface to the VRF:

switch# configure terminal

switch(config)# vrf context NewVRF

switch(config)# router ospf 201

switch(config)# interface ethernet 1/2

switch(config-if)# vrf member NewVRF

switch(config-if)# ip address 192.0.2.1/16

switch(config-if)# ip router ospf 201 area 0

switch(config)# copy running-config startup-config

Verifying the OSPFv2 Configuration

To display the OSPFv2 configuration, perform one of the following tasks:

Command

Purpose

show ip ospf

Displays the OSPFv2 configuration.

show ip ospf border-routers [vrf {vrf-name | all | default | management}]

Displays the OSPFv2 border router configuration.

show ip ospf database [vrf {vrf-name | all | default | management}]

Displays the OSPFv2 link-state database summary.

show ip ospf interface number [vrf {vrf-name | all | default | management}]

Displays the OSPFv2 interface configuration.

show ip ospf lsa-content-changed-list neighbor-id interface-type number [vrf {vrf-name | all | default | management}]

Displays the OSPFv2 LSAs that have changed.

show ip ospf neighbors [neighbor-id] [detail] [interface-type number] [vrf {vrf-name | all | default | management}] [summary]

Displays the list of OSPFv2 neighbors.

show ip ospf request-list neighbor-id interface-type number [vrf {vrf-name | all | default | management}]

Displays the list of OSPFv2 link-state requests.

show ip ospf retransmission-list neighbor-id interface-type number [vrf {vrf-name | all | default | management}]

Displays the list of OSPFv2 link-state retransmissions.

show ip ospf route [ospf-route] [summary] [vrf {vrf-name | all | default | management}]

Displays the internal OSPFv2 routes.

show ip ospf summary-address [vrf {vrf-name | all | default | management}]

Displays information about the OSPFv2 summary addresses.

show ip ospf virtual-links [brief] [vrf {vrf-name | all | default | management}]

Displays information about OSPFv2 virtual links.

show ip ospf vrf {vrf-name | all | default | management}

Displays information about VRF-based OSPFv2 configuration.

show running-configuration ospf

Displays the current running OSPFv2 configuration.

Monitoring OSPFv2

To display OSPFv2 statistics, use the following commands:

Command

Purpose

show ip ospf policy statistics area area-id filter-list {in | out} [vrf {vrf-name | all | default | management}]

Displays the OSPFv2 route policy statistics for an area.

show ip ospf policy statistics redistribute {bgp id | direct | eigrp id | isis id | ospf id | rip id | static} [vrf {vrf-name | all | default | management}]

Displays the OSPFv2 route policy statistics.

show ip ospf statistics [vrf {vrf-name | all | default | management}]

Displays the OSPFv2 event counters.

show ip ospf traffic [interface-type number] [vrf {vrf-name | all | default | management}]

Displays the OSPFv2 packet counters.

Configuration Examples for OSPFv2

The following example shows how to configure OSPFv2:

feature ospf

router ospf 201

router-id 290.0.2.1

interface ethernet 1/2

ip router ospf 201 area 0.0.0.10

ip ospf authentication

ip ospf authentication-key 0 mypass

OSPF RFC Compatibility Mode Example

The following example shows how to configure OSPF to be compatible with routers that comply with RFC 1583:

Note You must configure RFC 1583 compatibility on any VRF that connects to routers running only RFC1583 compatible OSPF.

switch#_configure terminal

switch(config)# feature ospf

switch(config)# router ospf Test1

switch(config-router)# rfc1583compatibility

switch(config-router)# vrf A

switch(config-router-vrf)# rfc1583compatibility

Additional References

For additional information related to implementing OSPF, see the following sections:

- Related Documents

- MIBs

Related Documents

Related Topic

Document Title

OSPFv2 CLI commands

Cisco Nexus 7000 Series NX-OS Unicast Routing Command Reference, Release 5.x

VDCs

Cisco Nexus 7000 Series NX-OS Virtual Device Context Configuration Guide, Release 5.x

OSPFv3 for IPv6 networks

Chapter 7, “Configuring OSPFv3”

Route maps

Chapter 16, “Configuring Route Policy Manager”

MIBs

MIBs

MIBs Link

- OSPF-MIB

- OSPF-TRAP-MIB

To locate and download MIBs, go to the following URL:

http://www.cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml

Feature History for OSPFv2

Table 6-3 lists the release history for this feature.

Table 6-3 Feature History for IOSPFv2

Feature Name

Releases

Feature Information

Passive interface

5.2(1)

Added support for setting the passive interface mode on all interfaces in the router or VRF.

BFD

5.0(2)

Added support for BFD. See the Cisco Nexus 7000 Series NX-OS Interfaces Configuration Guide, Release 5.x, for more information.

OSPFv2

4.0(1)

This feature was introduced.

Configuring GLBP

This chapter describes how to configure the Gateway Load Balancing Protocol (GLBP) on the Cisco NX-OS device.

This chapter includes the following sections:

- Information About GLBP

- Licensing Requirements for GLBP

- Prerequisites for GLBP

- Guidelines and Limitations for GLBP

- Default Settings

- Configuring GLBP

- Verifying the GLBP Configuration

- Configuration Examples for GLBP

- Additional References

- Feature History for GLBP

Information About GLBP

GLBP provides path redundancy for IP by sharing protocol and Media Access Control (MAC) addresses between redundant gateways. Additionally, GLBP allows a group of Layer 3 routers to share the load of the default gateway on a LAN. A GLBP router can automatically assume the forwarding function of another router in the group if the other router fails.

This section includes the following topics:

- GLBP Overview

- GLBP Active Virtual Gateway

- GLBP Virtual MAC Address Assignment

- GLBP Virtual Gateway Redundancy

- GLBP Virtual Forwarder Redundancy

- GLBP Authentication

- GLBP Load Balancing and Tracking

- High Availability and Extended Nonstop Forwarding

- Virtualization Support

GLBP Overview

GLBP provides automatic gateway backup for IP hosts configured with a single default gateway on an IEEE 802.3 LAN. Multiple routers on the LAN combine to offer a single virtual first-hop IP gateway while sharing the IP packet forwarding load. Other routers on the LAN might act as redundant GLBP gateways that become active if any of the existing forwarding gateways fail.

GLBP performs a similar function to the Hot Standby Redundancy Protocol (HSRP) and the Virtual Router Redundancy Protocol (VRRP). HSRP and VRRP allow multiple routers to participate in a virtual group configured with a virtual IP address. These protocols elect one member as the active router to forward packets to the virtual IP address for the group. The other routers in the group are redundant until the active router fails.

GLBP performs an additional load balancing function that the other protocols do not provide. GLBP load balances over multiple routers (gateways) using a single virtual IP address and multiple virtual MAC addresses. GLBP shares the forwarding load among all routers in a GLBP group instead of allowing a single router to handle the whole load while the other routers remain idle. You configure each host with the same virtual IP address, and all routers in the virtual group participate in forwarding packets. GLBP members communicate between each other using periodic hello messages.

GLBP Active Virtual Gateway

GLBP prioritizes gateways to elect an active virtual gateway (AVG). If multiple gateways have the same priority, the gateway with the highest real IP address becomes the AVG. The AVG assigns a virtual MAC address to each member of the GLBP group. Each member is the active virtual forwarder (AVF) for its assigned virtual MAC address, forwarding packets sent to its assigned virtual MAC address.

The AVG also answers Address Resolution Protocol (ARP) requests for the virtual IP address. Load sharing is achieved when the AVG replies to the ARP requests with different virtual MAC addresses.

Note Packets received on a routed port destined for the GLBP virtual IP address terminate on the local router, regardless of whether that router is the active GLBP router or a redundant GLBP router. This termination includes ping and Telnet traffic. Packets received on a Layer 2 (VLAN) interface destined for the GLBP virtual IP address terminate on the active router.

GLBP Virtual MAC Address Assignment

The AVG assigns the virtual MAC addresses to each member of the group. The group members request a virtual MAC address after they discover the AVG through hello messages. The AVG assigns the next MAC address based on the load-balancing algorithm selected (see the “GLBP Load Balancing and Tracking” section). A gateway that is assigned with a virtual MAC address by the AVG is the primary virtual forwarder. The other members of the GLBP group that learn the virtual MAC addresses from hello messages are secondary virtual forwarders.

GLBP Virtual Gateway Redundancy

GLBP provides virtual gateway redundancy. A member in a group can be in the active, standby, or listen state. GLBP uses a priority algorithm to elect one gateway as the AVG and elect another gateway as the standby virtual gateway. The remaining gateways go into the listen state. You can configure the GLBP priority on each gateway. If the GLBP priority is identical on multiple gateways, GLBP uses the gateway with the highest IP address as the AVG.

If an AVG fails, the standby virtual gateway assumes responsibility for the virtual IP address. GLBP elects a new standby virtual gateway from the gateways in the listen state.

GLBP Virtual Forwarder Redundancy

GLBP provides virtual forwarder redundancy. Virtual forwarder redundancy is similar to virtual gateway redundancy with an active virtual forwarder (AVF). If the AVF fails, a secondary virtual forwarder in the listen state assumes responsibility for the virtual MAC address. This secondary virtual forwarder is also a primary virtual forwarder for a different virtual MAC address. GLBP migrates hosts away from the old virtual MAC address of the failed AVF, using the following two timers:

- Redirect timer—Specifies the interval during which the AVG continues to redirect hosts to the old virtual MAC address. When the redirect time expires, the AVG stops using the old virtual MAC address in ARP replies, although the secondary virtual forwarder continues to forward packets that were sent to the old virtual MAC address.

- Secondary hold timer—Specifies the interval during which the virtual MAC address is valid. When the secondary hold time expires, GLBP removes the virtual MAC address from all gateways in the GLBP group and load balances the traffic over the remaining AVFs. The expired virtual MAC address becomes eligible for reassignment by the AVG.

GLBP uses hello messages to communicate the current state of the timers.

In Figure 18-1, router A is the AVG for a GLBP group and is responsible for the virtual IP address 192.0.2.1. Router A is also an AVF for the virtual MAC address 0007.b400.0101. Router B is a member of the same GLBP group and is designated as the AVF for the virtual MAC address 0007.b400.0102. Client 1 has a default gateway IP address of 192.0.2.1, the virtual IP address, and a gateway MAC address of 0007.b400.0101 that points to router A. Client 2 shares the same default gateway IP address but receives the gateway MAC address 0007.b400.0102 because router B is sharing the traffic load with router A.

Figure 18-1 GLBP Topology

If router A becomes unavailable, client 1 does not lose access to the WAN because router B assumes responsibility for forwarding packets sent to the virtual MAC address of router A and for responding to packets sent to its own virtual MAC address. Router B also assumes the role of the AVG for the entire GLBP group. Communication for the GLBP members continues despite the failure of a router in the GLBP group.

GLBP Authentication

GLBP has three authentication types:

- MD5 authentication

- Plain text authentication

- No authentication

MD5 authentication provides greater security than plain text authentication. MD5 authentication allows each GLBP group member to use a secret key to generate a keyed MD5 hash that is part of the outgoing packet. At the receiving end, a keyed hash of an incoming packet is generated. If the hash within the incoming packet does not match the generated hash, the packet is ignored. The key for the MD5 hash can either be given directly in the configuration using a key string or supplied indirectly through a key chain.

You can also choose to use a simple password in plain text to authenticate GLBP packets, or choose no authentication for GLBP.

GLBP rejects packets in any of the following cases:

- The authentication schemes differ on the router and in the incoming packet.

- MD5 digests differ on the router and in the incoming packet.

- Text authentication strings differ on the router and in the incoming packet.

GLBP Load Balancing and Tracking

You can configure the following load-balancing methods for GLBP:

- Round-robin—GLBP cycles through the virtual MAC addresses sent in ARP replies, load balancing the traffic across all the AVFs.

- Weighted—AVG uses the advertised weight for an AVF to decide the load directed to the AVF. A higher weight means that the AVG directs more traffic to the AVF.

- Host dependent—GLBP uses the MAC address of the host to determine which virtual MAC address to direct the host to use. This algorithm guarantees that a host gets the same virtual MAC address if the number of virtual forwarders does not change.

The default for IPv4 networks is round-robin. You can disable all load balancing for GLBP on an interface. If you do not configure load balancing, the AVG handles all traffic for the hosts while the other GLBP group members are in standby or listen mode.

You can configure GLBP to track an interface or routes and enable the secondary virtual forwarder to take over if a tracked link goes down. GLBP tracking uses weighted load-balancing to determine whether a GLBP group member acts as an AVF. You must configure the initial weighting values and optional thresholds to enable or disable this group member as an AVF. You can also configure the interface to track and the value that reduces the interface’s weighting if the interface goes down. When the GLBP group weighting drops below the lower threshold, the member is no longer an AVF and a secondary virtual forwarder takes over. When the weighting rises above the upper threshold, the member can resume its role as an AVF.

Figure 18-2 shows an example of GLBP tracking and weighting.

Figure 18-2 GLBP Object Tracking and Weighting

In Figure 18-2, the Ethernet 1/2 interface on router 1 is the gateway for host 1 (the AVF for virtual MAC address, vMAC1), while Ethernet 2/2 on router 2 acts as a secondary virtual forwarder for Host 1. Ethernet 1/2 tracks Ethernet 3/1, which is the network connection for router 1. If Ethernet 3/1 goes down, the weighting for Ethernet 1/2 drops to 90. Ethernet 2/2 on router 2 preempts Ethernet 1/2 and takes over as AVF because it has the default weighting of 100 and is configured to preempt the AVF.

See the “Configuring GLBP Weighting and Tracking” section for details about configuring weighting and tracking.

High Availability and Extended Nonstop Forwarding

GLBP supports high availability through stateful restarts and stateful switchovers. A stateful restart occurs when the GLBP process fails and is restarted. A stateful switchover occurs when the active supervisor switches to the standby supervisor. Cisco NX-OS applies the run-time configuration after the switchover.

If GLBP hold timers are configured for short time periods, these timers might expire during a controlled switchover or in-service software upgrade (ISSU). GLBP supports extended non-stop forwarding (NSF) to temporarily extend these GLBP hold timers during a controlled switchover or ISSU.

With extended NSF configured, GLBP sends hello messages with the extended timers. GLBP peers update their hold timers with these new values. The extended timers prevent unnecessary GLBP state changes during the switchover or ISSU. After the switchover or ISSU event, GLBP restores the hold timers to their original configured values. If the switchover fails, GLBP restores the hold timers after the extended hold timer values expire.

See the “Configuring Extended Hold Timers for GLBP” section for more information.

Virtualization Support

GLBP supports virtual routing and forwarding (VRF) instances. VRFs exist within virtual device contexts (VDCs). By default, Cisco NX-OS places you in the default VDC and default VRF unless you specifically configure another VDC and VRF.

If you change the VRF membership of an interface, Cisco NX-OS removes all Layer 3 configuration, including GLBP.

For more information, see the Cisco Nexus 7000 Series NX-OS Virtual Device Context Configuration Guide, Release 5.x, and see Chapter14, “Configuring Layer 3 Virtualization”

Licensing Requirements for GLBP

The following table shows the licensing requirements for this feature:

Product

License Requirement

Cisco NX-OS

GLBP requires no license. Any feature not included in a license package is bundled with the Cisco NX-OS system images and is provided at no extra charge to you. For a complete explanation of the Cisco NX-OS licensing scheme, see the Cisco NX-OS Licensing Guide.

Prerequisites for GLBP

GLBP has the following prerequisites:

- Globally enable the GLBP feature (see the “Enabling GLBP” section).

- You can only configure GLBP on Layer 3 interfaces (see the Cisco Nexus 7000 Series NX-OS Interfaces Configuration Guide, Release 5.x, and the Cisco DCNM Interfaces Configuration Guide, Release 5.x ).

- If you configure VDCs, install the Advanced Services license and enter the desired VDC (see the Cisco Nexus 7000 Series NX-OS Virtual Device Context Configuration Guide, Release 5.x).

Guidelines and Limitations for GLBP

GLBP has the following configuration guidelines and limitations:

- You should configure all customization options for GLBP on all GLBP member gateways before enabling a GLBP group by configuring a virtual IP address.

- You must configure an IP address for the interface that you configure GLBP on and enable that interface before GLBP becomes active.

- The GLBP virtual IP address must be in the same subnet as the interface IP address.

- We recommend that you do not configure more than one first-hop redundancy protocol on the same interface.

- Cisco NX-OS removes all Layer 3 configuration on an interface when you change the VDC, interface VRF membership, port channel membership, or when you change the port mode to Layer 2.

- Cisco NX-OS does not support GLBP group configuration on interface secondary subnets.

- Cisco NX-OS does not support GLBP for IPv6.

Default Settings

Table 18-1 lists the default settings for GLBP parameters.

Table 18-1 Default GLBP Parameters

Parameters

Default

Authentication

No authentication

Extended hold timer

10 seconds

Forwarder preemption delay

30 seconds

Forwarder timeout

14400 seconds

Hello timer

3 seconds

Hold timer

10 seconds

GLBP feature

Disabled

Load balancing

Round robin

Preemption

Disabled

Priority

100

Redirect timer

600 seconds

Weighting

100

Configuring GLBP

This section includes the following topics:

- Enabling GLBP

- Configuring GLBP Authentication

- Configuring GLBP Load Balancing

- Configuring GLBP Weighting and Tracking

- Customizing GLBP

- Configuring Extended Hold Timers for GLBP

- Enabling a GLBP Group

Note If you are familiar with the Cisco IOS CLI, be aware that the Cisco NX-OS commands for this feature might differ from the Cisco IOS commands that you would use.

Enabling GLBP

You must enable GLBP before you can configure and enable any GLBP groups.

BEFORE YOU BEGIN

Ensure that you are in the correct VDC (or use the switchto vdc command).

DETAILED STEPS

To enable GLBP, use the following command in global configuration mode:

Command

Purpose

feature glbp

Example:

switch(config)# feature glbp

Enables GLBP.

To disable GLBP in a VDC and remove all associated configuration, use the following command in global configuration mode:

Command

Purpose

no feature glbp

Example:

switch(config)# no feature glbp

Disables GLBP in a VDC.

Configuring GLBP Authentication

You can configure GLBP to authenticate the protocol using cleartext or an MD5 digest. MD5 authentication uses a key chain (see the Cisco Nexus 7000 Series NX-OS Security Configuration Guide, Release 5.x).

BEFORE YOU BEGIN

Ensure that you are in the correct VDC (or use the switchto vdc command).

Enable GLBP (see the “Enabling GLBP” section).

Note You must configure the same authentication and keys on all members of the GLBP group.

SUMMARY STEPS

1. configure terminal

2. interface interface-type slot/port

3. ip ip-address/length

4. glbp group-number

5. authentication text string

or

authentication md5 {key-chain key-chain | key-string {text | encrypted text}

6. ip [ip-address [secondary]]

7. (Optional) show glbp [group group-number]

8. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

interface interface-type slot/port

Example:

switch(config)# interface ethernet 1/2

switch(config-if)#

Enters interface configuration mode.

Step 3

ip ip-address/length

Example:

switch(config-if)# ip 192.0.2.1/8

Configures the IPv4 address for the interface.

Step 4

glbp group-number

Example:

switch(config-if)# glbp 1

switch(config-if-glbp)#

Creates a GLBP group and enters GLBP configuration mode. The range is from 0 to 1024.

Step 5

authentication text string

Example:

switch(config-if-glbp)# authentication text mypassword

Configures cleartext authentication for GLBP on this interface.

authentication md5 {key-chain key-chain | key-string {text | encrypted text}

Example:

switch(config-if-glbp)# authentication md5 key-chain glbp-keys

Configures MD5 authentication for GLBP on this interface.

Step 6

ip [ip-address [secondary]]

Example:

switch(config-if-glbp)# ip 192.0.2.10

Enables GLBP on an interface and identifies the primary IP address of the virtual gateway.

After you identify a primary IP address, you can use the glbp group ip command again with the secondary keyword to indicate additional IP addresses supported by this group. If you only use the ip keyword, GLBP learns the virtual IP address from the neighbors.

Step 7

show glbp [group group-number]

Example:

switch(config-if-glbp)# show glbp 1

(Optional) Displays GLBP information.

Step 8

copy running-config startup-config

Example:

switch(config-if-glbp)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to configure MD5 authentication for GLBP on Ethernet 1/2 after creating the key chain:

switch# configure terminal

switch(config)# key chain glbp-keys

switch(config-keychain)# key 0

switch(config-keychain-key)# key-string 7 zqdest

switch(config-keychain-key) accept-lifetime 00:00:00 Jun 01 2008 23:59:59 Sep 12 2008

switch(config-keychain-key) send-lifetime 00:00:00 Jun 01 2008 23:59:59 Aug 12 2008

switch(config-keychain-key) key 1

switch(config-keychain-key) key-string 7 uaeqdyito

switch(config-keychain-key) accept-lifetime 00:00:00 Aug 12 2008 23:59:59 Dec 12 2008

switch(config-keychain-key) send-lifetime 00:00:00 Sep 12 2008 23:59:59 Nov 12 2008

switch(config)# interface ethernet 1/2

switch(config-if)# glbp 1

switch(config-if-glbp)# authenticate md5 key-chain glbp-keys

switch(config-if-glbp)# copy running-config startup-config

Configuring GLBP Load Balancing

You can configure GLBP to use load balancing based on round-robin, weighted, or host-dependent methods (see the “GLBP Load Balancing and Tracking” section).

To configure GLBP load balancing, use the following command in GLBP configuration mode:

Command

Purpose

load-balancing [host-dependent | round-robin | weighted]

Example:

switch(config-if-glbp)# load-balancing weighted

Sets the GLBP load-balancing method. The default is round-robin.

Configuring GLBP Weighting and Tracking

You can configure GLBP weighting values and object tracking to work with the GLBP weighted load-balancing method.

You can optionally configure the interface to preempt an AVF if the interface was originally assigned with the virtual MAC address or if this interface has a higher weight than the AVF.

BEFORE YOU BEGIN

Ensure that you are in the correct VDC (or use the switchto vdc command).

Enable GLBP (see the “Enabling GLBP” section).

SUMMARY STEPS

1. configure terminal

2. track object-id interface interface-type number {ip routing | line-protocol}

track object-id ip route ip-prefix/length reachability

3. interface interface-type slot/port

4. ip ip-address/length

5. glbp group-number

6. weighting maximum [lower lower] [upper upper]

7. weighting track object-number [decrement value]

8. (Optional) forwarder preempt [delay minimum seconds]

9. ip [ip-address [secondary]]

10. (Optional) show glbp interface-type number

11. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

track object-id interface interface-type number {ip routing | line-protocol}

Example:

switch(config)# track 1 interface ethernet 2/2 line-protocol

switch(config-track#

Configures the interface that this GLBP interface tracks. Changes in the state of the interface affect the priority of this GLBP interface as follows:

- You configure the interface and corresponding object number that you use with the track command in GLBP configuration mode.

- The line-protocol keyword tracks whether the interface is up. The ip keyword also checks that IP routing is enabled on the interface and an IP address is configured.

track object-id ip route ip-prefix/length reachability

Example:

switch(config)# track 2 ip route 192.0.2.0/8 reachability

switch(config-track#

Creates a tracked object for a route and enters tracking configuration mode. The object-id range is from 1 to 500.

Step 3

interface interface-type slot/port

Example:

switch(config)# interface ethernet 1/2

switch(config-if)#

Enters interface configuration mode.

Step 4

ip ip-address/length

Example:

switch(config-if)# ip 192.0.2.1/8

Configures the IPv4 address for the interface.

Step 5

glbp group-number

Example:

switch(config-if)# glbp 1

switch(config-if-glbp)#

Creates a GLBP group and enters GLBP configuration mode.

Step 6

weighting maximum [lower lower] [upper upper]

Example:

switch(config-if-glbp)# weighting 110 lower 95 upper 105

Specifies the initial weighting value and the upper and lower thresholds for a GLBP gateway. The maximum range is from 1 to 254. The default weighting value is 100. The lower range is from 1 to 253. The upper range is from 1 to 254.

Step 7

weighting track object-number [decrement value]

Example:

switch(config-if-glbp)# weighting track 2 decrement 20

Specifies an object to be tracked that affects the weighting of a GLBP gateway. The value argument specifies a reduction in the weighting of a GLBP gateway when a tracked object fails. The range is from 1 to 255.

Step 8

forwarder preempt [delay minimum seconds]

Example:

switch(config-if-glbp)# forwarder preempt delay minimum 60

(Optional) Configures the router to take over as AVF for a GLBP group if the current AVF for a GLBP group falls below its low weighting threshold. The range is from 0 to 3600 seconds.

This command is enabled by default with a delay of 30 seconds.

Step 9

ip [ip-address [secondary]]

Example:

switch(config-if-glbp)# ip 192.0.2.10

Enables GLBP on an interface and identifies the primary IP address of the virtual gateway.

After you identify a primary IP address, you can use the glbp group ip command again with the secondary keyword to indicate additional IP addresses supported by this group. If you only use the ip keyword, GLBP learns the virtual IP address from the neighbors.

Step 10

show glbp interface-type number

Example:

switch(config-if-glbp)# show glbp ethernet 1/2

(Optional) Displays GLBP information for an interface.

Step 11

copy running-config startup-config

Example:

switch(config-if-glbp)# copy running-config startup-config

(Optional) Saves this configuration change.

The following example shows how to configure GLBP weighting and tracking on Ethernet 1/2:

switch# configure terminal

switch(config)# track 2 interface ethernet 2/2 ip routing

switch(config)# interface ethernet 1/2

switch(config-if)# glbp 1

switch(config-if-glbp)# weighting 110 lower 95 upper 105

switch(config-if-glbp)# weighting track 2 decrement 20

switch(config-if-glbp)# copy running-config startup-config

Customizing GLBP

Customizing the behavior of GLBP is optional. Be aware that as soon as you enable a GLBP group by configuring a virtual IP address, that group is operational. If you enable a GLBP group before you customize GLBP, the router could take over control of the group and become the AVG before you finish customizing the feature. If you plan to customize GLBP, you should do so before enabling GLBP.

To customize GLBP, use the following commands in GLBP configuration mode:

Command

Purpose

timers [msec] hellotime [msec] holdtime

Example:

switch(config-if-glbp)# timers 5 18

Configures the following hello and hold times for this GLBP member:

- hellotime —The interval between successive hello packets sent by the AVG in a GLBP group. The range is from 1 to 60 seconds or from 250 to 60000 milliseconds. The default value is 3 seconds.

- holdtime —The interval before the virtual gateway and virtual forwarder information in the hello packet is considered invalid. The range is from 2 to 180 seconds or from 1020 to 180000 milliseconds. The default is 10 seconds.

The optional msec keyword specifies that the argument is expressed in milliseconds, instead of the default seconds.

timers redirect redirect timeout

Example:

switch(config-if-glbp)# timers redirect 600 7200

Configures the following timers:

- redirect —The time interval in seconds during which the AVG continues to redirect clients to an AVF. The range is from 0 to 3600 seconds. The default is 600 seconds.

- timeout— The interval in seconds before a secondary virtual forwarder becomes invalid. The range is from 610 to 64800 seconds. The default is 14,440 seconds.

priority level

Example:

switch(config-if-glbp)# priority 254

Sets the priority level used to select the AVG in a GLBP group. The range is from 1 to 255. The default is 100.

preempt [delay minimum seconds]

Example:

switch(config-if-glbp)# preempt delay minimum 60

Configures the router to take over as AVG for a GLBP group if it has a higher priority than the current AVG. This command is disabled by default.

Use the optional delay minimum keywords and the seconds argument to specify a minimum delay interval in seconds before preemption of the AVG takes place.

The seconds range is from 0 to 3600 seconds. The minimum delay default is 3600 seconds.

Configuring Extended Hold Timers for GLBP

You can configure GLBP to use extended hold timers to support extended NSF during a controlled (graceful) switchover or ISSU, including software upgrades and supervisor switchovers. You should configure extended hold timers on all GLBP gateways (see the “High Availability and Extended Nonstop Forwarding” section).

Note You must configure extended hold timers on all GLBP gateways if you configure non-default extended hold timers. You can configure different extended hold timer values on each GLBP gateway, based on the expected system switchover delays.

To configure GLBP extended hold timers, use the following command in global configuration mode:

Command

Purpose

glbp timers extended-hold [timer]

Example:

switch(config)# glbp timers extended-hold 30

Sets the GLBP extended hold timer, in seconds. The timer range is from 10 to 255. The default is 10.

Use the show glbp command command to display the extended hold time.

Enabling a GLBP Group

You can configure the virtual IP address on an interface to enable the GLBP group. You must configure each gateway in the GLBP group with the same group number. The GLBP member can learn all other required parameters from another GLBP member.

BEFORE YOU BEGIN

Ensure that you are in the correct VDC (or use the switchto vdc command).

Enable GLBP (see the “Enabling GLBP” section).

SUMMARY STEPS

1. configure terminal

2. interface interface-type slot/port

3. ip ip-address/length

4. glbp group-number

5. ip [ip-address [secondary]]

6. (Optional) show glbp [group group-number] [brief]

7. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

interface interface-type slot/port

Example:

switch(config)# interface ethernet 1/2

switch(config-if)#

Enters interface configuration mode.

Step 3

ip ip-address/length

Example:

switch(config-if)# ip 192.0.2.1/8

Configures the IPv4 address for the interface.

Step 4

glbp group-number

Example:

switch(config-if)# glbp 1

switch(config-if-glbp)#

Creates a GLBP group and enters GLBP configuration mode.

Step 5

ip [ip-address [secondary]]

Example:

switch(config-if-glbp)# ip 192.0.2.10

Enables GLBP on an interface and identifies the virtual IP address. The virtual IP should be in the same subnet as the interface IP address.

After you identify a virtual IP address, you can use the glbp group ip command again with the secondary keyword to indicate additional IP addresses supported by this group. If you only use the ip keyword, GLBP learns the virtual IP address from the neighbors.

Step 6

show glbp [group group-number] [brief]

Example:

switch(config-if-glbp)# show glbp brief

(Optional) Displays a brief summary of GLBP information.

Step 7

copy running-config startup-config

Example:

switch(config-if-glbp)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to enable GLBP on Ethernet 1/2:

switch# configure terminal

switch(config)# interface ethernet 1/2

switch(config-if)# glbp 1

switch(config-if-glbp)# ip 192.0.2.10

Verifying the GLBP Configuration

To display GLBP configuration information, perform one of the following tasks:

Command

Purpose

show glbp [group group-number]

Displays the GLBP status for all or one group.

show glbp capability

Displays the GLBP capability for all or one group.

show glbp interface interface-type slot/port

Displays the GLBP status for an interface.

show glbp interface interface-type slot/port [active] [disabled] [init] [listen] [standby]

Displays the GLBP status for a group or interface for virtual forwarders in the selected state.

show glbp interface interface-type slot/port [active] [disabled] [init] [listen] [standby] brief

Displays a brief summary of the GLBP status for a group or interface for virtual forwarders in the selected state.

Configuration Examples for GLBP

The following example shows how to enable GLBP on an interface, with MD5 authentication, interface tracking, and weighted load balancing:

key chain glbp-keys

key 0

key-string 7 zqdest

accept-lifetime 00:00:00 Jun 01 2008 23:59:59 Sep 12 2008

send-lifetime 00:00:00 Jun 01 2008 23:59:59 Aug 12 2008

key 1

key-string 7 uaeqdyito

accept-lifetime 00:00:00 Aug 12 2008 23:59:59 Dec 12 2008

send-lifetime 00:00:00 Sep 12 2008 23:59:59 Nov 12 2008

feature glbp

track 2 interface ethernet 2/2 ip

interface ethernet 1/2

ip address 192.0.2.2/8

glbp 1

authentication md5 key-chain glbp-keys

weighting 110 lower 95 upper 105

weighting track 2 decrement 20

ip 192.0.2.10

no shutdown

Additional References

For additional information related to implementing GLBP, see the following sections:

- Related Documents

- Standards

Related Documents

Related Topic

Document Title

Configuring the Hot Standby Redundancy protocol

Chapter 19, “Configuring HSRP”

Configuring the Virtual Router Redundancy protocol

Chapter 20, “Configuring VRRP”

GLBP CLI commands

Cisco Nexus 7000 Series NX-OS Unicast Routing Command Reference, Release 5.x

Configuring high availability

Cisco Nexus 7000 Series NX-OS High Availability and Redundancy Guide, Release 5.x

Standards

Standards

Title

No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.

—

Feature History for GLBP

Table 18-2 lists the release history for this feature.

Table 18-2 Feature History for GLBP

Feature Name

Releases

Feature Information

GLBP

4.0(1)

This feature was introduced.

IETF RFCs supported by Cisco NX-OS Unicast Features, Release 5.x

This appendix lists the IETF RFCs supported in Cisco NX-OS Release 5.x.

BGP RFCs

RFCs

Title

RFC 1997

BGP Communities Attribute

RFC 2385

Protection of BGP Sessions via the TCP MD5 Signature Option

RFC 2439

BGP Route Flap Damping

RFC 2519

A Framework for Inter-Domain Route Aggregation

RFC 2545

Use of BGP-4 Multiprotocol Extensions for IPv6 Inter-Domain Routing

RFC 2858

Multiprotocol Extensions for BGP-4

RFC 3065

Autonomous System Confederations for BGP

RFC 3392

Capabilities Advertisement with BGP-4

RFC 4271

A Border Gateway Protocol 4 (BGP-4)

RFC 4273

Definitions of Managed Objects for BGP-4

RFC 4456

BGP Route Reflection: An Alternative to Full Mesh Internal BGP (IBGP)

RFC 4486

Subcodes for BGP Cease Notification Message

RFC 4724

Graceful Restart Mechanism for BGP

RFC 4893

BGP Support for Four-octet AS Number Space

RFC 5004

Avoid BGP Best Path Transitions from One External to Another

RFC 53961

Textual Representation of Autonomous System (AS) Numbers

RFC 5668

4-Octet AS Specific BGP Extended Community

draft-ietf-idr-bgp4-mib-15.txt

BGP4-MIB

draft-kato-bgp-ipv6-link-local-00.txt

BGP4+ Peering Using IPv6 Link-local Address

1.RFC 5396 is partially supported. The asplain and asdot notations are supported, but the asdot+ notation is not.

First-Hop Redundancy Protocols RFCs

RFCs

Title

RFC 2281

Hot Standby Redundancy Protocol

RFC 3768

Virtual Router Redundancy Protocol

IP Services RFCs

RFCs

Title

RFC 768

UDP

RFC 791

IP

RFC 792

ICMP

RFC 793

TCP

RFC 826

ARP

RFC 1027

Proxy ARP

RFC 1591

DNS Client

RFC 1812

IPv4 routers

RFC 4022

TCP-MIB

RFC 4292

IP-FORWARDING-TABLE-MIB

RFC 4293

IP-MIB

IPv6 RFCs

RFCs

Title

RFC 1981

Path MTU Discovery for IP version 6

RFC 2373

IP Version 6 Addressing Architecture

RFC 2374

An Aggregatable Global Unicast Address Format

RFC 2460

Internet Protocol, Version 6 (IPv6) Specification

RFC 2461

Neighbor Discovery for IP Version 6 (IPv6)

RFC 2462

IPv6 Stateless Address Autoconfiguration

RFC 2463

Internet Control Message Protocol (ICMPv6) for the Internet Protocol Version 6 (IPv6) Specification

RFC 2464

Transmission of IPv6 Packets over Ethernet Networks

RFC 3152

Delegation of IP6.ARPA

RFC 3162

RADIUS and IPv6

RFC 3513

Internet Protocol Version 6 (IPv6) Addressing Architecture

RFC 3596

DNS Extensions to Support IP version 6

RFC 4193

Unique Local IPv6 Unicast Addresses

IS-IS RFCs

RFCs

Title

RFC 1142

OSI 10589 Intermediate system to intermediate system intra-domain routing exchange protocol

RFC 1195

Use of OSI IS-IS for routing in TCP/IP and dual environment

RFC 2763, RFC 5301

Dynamic Hostname Exchange Mechanism for IS-IS

RFC 2966, RFC 5302

Domain-wide Prefix Distribution with Two-Level IS-IS

RFC 2972

IS-IS Mesh Groups

RFC 3277

IS-IS Transient Blackhole Avoidance

RFC 3373, RFC 5303

Three-Way Handshake for IS-IS Point-to-Point Adjacencies

RFC 3567, RFC 5304

IS-IS Cryptographic Authentication

RFC 3784, RFC 5305

IS-IS Extensions for Traffic Engineering

RFC 3847, RFC 5306

Restart Signaling for IS-IS

RFC 4205, RFC 5307

IS-IS Extensions in Support of Generalized Multi-Protocol Label Switching

draft-ietf-isis-igp-p2p-over-lan-06.txt

Internet Draft Point-to-point operation over LAN in link-state routing protocols

OSPF RFCs

RFCs

Title

RFC 2328

OSPF Version 2

RFC 2740

OSPF for IPv6

RFC 3623

Graceful OSPF Restart

RFC 3101

The OSPF Not-So-Stubby Area (NSSA) Option

RFC 2370

The OSPF Opaque LSA Option

RFC 3137

OSPF Stub Router Advertisement

draft-ietf-ospf-ospfv3-graceful-restart-04.txt

OSPFv3 Graceful Restart

RIP RFCs

RFCs

Title

RFC 2453

RIP Version 2

RFC 2082

RIP-2 MD5 Authentication

Configuration Limits for Cisco NX-OS Layer 3 Unicast Features

The configuration limits are documented in the Cisco Nexus 7000 Series NX-OS Verified Scalability Guide.

Glossary

A

ABR

See area border router.

address family

A specific type of network addressing supported by a routing protocol. Examples include IPv4 unicast and IPv4 multicast.

adjacency

Two OSPF routers that have compatible configurations and have synchronized their link-state databases.

administrative distance

A rating of the trustworthiness of a routing information source. In general, the higher the value, the lower the trust rating.

area

A logical division of routers and links within an OSPF domain that creates separate subdomains. LSA flooding is contained within an area.

area border router

A router that connects one OSPF area to another OSPF area.

ARP

Address resolution protocol. ARP discovers the MAC address for a known IPv4 address.

AS

See autonomous system.

ASBR

See autonomous system border router .

attributes

Properties of a route that are sent in BGP UPDATE messages. These attributes include the path to the advertised destination as well as configurable options that modify the best path selection process.

autonomous system

A network controlled by a single technical administration entity.

autonomous system border router

A router that connect a an OSPF autonomous system to an external autonomous system.

AVF

Active virtual forwarder. A gateway within a GLBP group elected to forward traffic for a specified virtual MAC address.

AVG

Active virtual gateway. One virtual gateway within a GLBP group is elected as the active virtual gateway and is responsible for the operation of the protocol.

B

backup designated router

See BDR.

bandwidth

The available traffic capacity of a link.

BDR

Backup designated router. An elected router in a multi-access OSPF network that acts as the backup if the designated router fails. All neighbors form adjacencies with the backup designated router (BDR) as well as the designated router.

BGP

Border Gateway Protocol. BGP is an interdomain or exterior gateway protocol.

BGP peer

A remote BGP speaker that is an established neighbor of the local BGP speaker.

BGP speaker

BGP-enabled router.

C

communication cost

Measure of the operating cost to route over a link.

converged

The point at which all routers in a network have identical routing information.

convergence

See converged.

D

dead interval

The time within which an OSPF router must receive a Hello packet from an OSPF neighbor. The dead interval is usually a multiple of the hello interval. If no Hello packet is received, the neighbor adjacency is removed.

default gateway

A router to which all unroutable packets are sent. Also called the router of last resort.

delay

The length of time required to move a packet from the source to the destination through the internetwork.

designated router

See DR.

DHCP

Dynamic Host Control Protocol.

Diffusing Update Algorithm

See DUAL.

distance vector

Defines routes by distance (for example, the number of hops to the destination) and direction (for example, the next-hop router) and then broadcasts to the directly connected neighbor routers.

DNS client

Domain Name System client. Communicates with DNS server to translate a hostname to an IP address.

DR

Designated router. An elected router in a multi-access OSPF network that sends LSAs on behalf of all its adjacent neighbors. All neighbors establish adjacency with only the designated router and the backup designated router.

DUAL

Diffusing Update Algorithm. EIGRP algorithm used to select optimal routes to a destination.

E

eBGP

External Border Gateway Protocol (BGP). Operates between external systems.

EIGRP

Enhanced Interior Gateway Protocol. A Cisco routing protocol that uses the Diffusing Update Algorithm to provide fast convergence and minimized bandwidth usage.

F

feasible distance

The lowest calculated distance to a network destination in EIGRP. The feasibility distance is the sum of the advertised distance from a neighbor plus the cost of the link to that neighbor.

feasible successor

Neighbors in EIGRP that advertise a shorter distance to the destination than the current feasibility distance.

FIB

Fowarding Information Base. The forwarding table on each module that is used to make the Layer 3 forwarding decisions per packet.

G

gateway

A switch or router that forwards Layer 3 traffic from a LAN to the rest of the network.

GLBP

Gateway Load Balancing Protocol. A Cisco proprietary protocol that provides high availability features to end hosts.

graceful restart

A feature that allows a router to remain in the data forwarding path while a routing protocol reboots.

H

hello interval

The configurable time between each Hello packet sent by an OSPF or EIGRP router.

hello packet

A special message used by OSPF or IS-IS to discover neighbors. Also acts as a keepalive messages between established neighbors.

high availability

The ability of a system or component to limit or avoid network disruption when a component fails.

hold time

In BGP, the maximum time limit allowed in BGP between update or keepalive messages. If this time is exceeded, the TCP connection between the BGP peers is closed.

In EIGRP, the maximum time allowed between EIGRP Hello messages. If this time is exceeded, the neighbor is declared unreachable.

hop count

The number of routers that can be traversed in a route. Used by RIP.

HSRP

Hot Standby Router Protocol.

I

iBGP

Internal Border Gateway Protocol (BGP). Operates within an autonomous system.

ICMP

Internet Control Message Protocol (ICMP)

IETF RFCs

Internet Engineering Task Force Request for Comments.

IGP

Interior Gateway Protocol. Used between routers within the same autonomous system.

instance

An independent, configurable entity, typically a protocol.

IP tunnels

A method of encapsulating packets within various Internet Protocols (IP) to interconnect communications between different networks.

IPv4

Internet Protocol version 4.

IPv6

Internet Protocol version 6.

IS-IS

Intermediate System to Intermediate System. An ISO interior gateway protocol.

K

keepalive

A special message sent between routing peers to verify and maintain communications between the pair.

key-chain management

A method of controlling authentication keys. See the Cisco Nexus 7000 Series NX-OS Security Configuration Guide .

L

link cost

An arbitrary number configured on an OSPF interface which is in shortest path first calculations.

link-state

Shares information about a link and link cost to neighboring routers.

link-state advertisement

See LSA.

LSA

Link-state advertisement. An OSPF message to share information on the operational state of a link, link cost, and other OSPF neighbor information.

link-state database

OSPF database of all LSAs received. OSPF uses this database to calculate the best path to each destination in the network.

link-state refresh

The time that OSPF floods the network with LSAs to ensure all OSPF routers have the same information.

load

The degree to which a network resource, such as a router, is busy.

load balancing

The distribution of network traffic across multiple paths to a given destination.

M

message digest

A one-way hash applied to a message using a shared password and appended to the message to authenticate the message and ensure the message has not been altered in transit.

metric

A standard of measurement, such as the path bandwidth, that is used by routing algorithms to determine the optimal path to a destination.

MD5 authentication digest

A cryptographic construction that is calculated based on an authentication key and the original message and sent along with the message to the destination. Allows the destination to determine the authenticity of the sender and guarantees that the message has not been tampered with during transmission.

MTU

Maximum transmission unit. The largest packet size that a network link transmits without fragmentation.

N

NDP

Neighbor Discovery Protocol. The protocol used by IPv6 to find the MAC address associated with an IPv6 address.

network layer reachability information

BGP network layer reachability information (NRLI). Contains the a list of network IP addresses and network masks for networks that are reachable from the advertising BGP peer.

next hop

The next router that a packet is sent to on its way to the destination address.

NSSA

Not-So-Stubby-Area. Limits AS external LSAs in an OSPF area.

O

OSPF

Open Shortest Path First. An IETF link-state protocol. OSPFv2 supports IPv4 and OSPFv3 supports IPv6.

P

path length

Sum of all link costs or the hop count that a packet experiences when routed from the source to the destination.

policy-based routing

The method of using route maps to alter the route selected for a packet.

R

redistribution

One routing protocol accepts route information from another routing protocol and advertises it in the local autonomous system.

Reliable Transport Protocol

Responsible for guaranteed, ordered delivery of EIGRP packets to all neighbors.

reliability

The dependability (usually described in terms of the bit-error rate) of each network link.

RIB

Routing Information Base. Maintains the routing table with directly connected routes, static routes, and routes learned from dynamic unicast routing protocols.

Route Policy Manager

The process that controls route maps and policy-based routing.

Routing Information Base

See RIB.

route map

A construct used to map a route or packet based on match criteria and optionally alter the route or packet based on set criteria. Used in route redistribution and policy-based routing.

route summarization

A process that replaces a series of related, specific routes in a route table with a more generic route.

router ID

A unique identifier used by routing protocols. If not manually configured, the routing protocol selects the highest IP address configured on the system.

S

SPF algorithm

Shortest Path First algorithm. Dijkstra’s algorithm used by OSPF to determine the shortest route through a network to a particular destination.

split horizon

Routes learned from an interface are not advertised back along the interface they were learned on, preventing the router from seeing its own route updates.

split horizon with poison reverse

Routes learned from an interface are set as unreachable and advertised back along the interface they were learned on, preventing the router from seeing its own route updates.

static route

A manually configured route.

stub area

An OSPF area that does not allow AS External (type 5) LSAs.

stub router

A router that has no direct connection to the main network and which routes to that network using a known remote router.

SVI

switched virtual interface.

U

U6FIB

Unicast IPv6 Forwarding Information Base.

UFIB

Unicast Forwarding Information Base for IPv4.

U6RIB

Unicast IPv6 Routing Information Base. The unicast routing table that gathers information from all routing protocols and updates the forwarding information base for each module.

URIB

Unicast Routing Information Base for IPv4. The unicast routing table that gathers information from all routing protocols and updates the forwarding information base for each module.

V

VDC

virtual device context. Used to split a physical system into secure, independent, logical systems.

virtualization

A method of making a physical entity act as multiple, independent logical entities.

VRF

virtual routing and forwarding. A method used to create separate, independent Layer 3 entities within a system.

VRRP

Virtual Router Redundancy Protocol.

Cisco Nexus 7000 Series NX-OS System Management Configuration Guide, Release 5.x

December 2011

TTHE SPECIFICATIONS AND INFORMATION REGARDING THE PRODUCTS IN THIS MANUAL ARE SUBJECT TO CHANGE WITHOUT NOTICE. ALL STATEMENTS, INFORMATION, AND RECOMMENDATIONS IN THIS MANUAL ARE BELIEVED TO BE ACCURATE BUT ARE PRESENTED WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED. USERS MUST TAKE FULL RESPONSIBILITY FOR THEIR APPLICATION OF ANY PRODUCTS.

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IN NO EVENT SHALL CISCO OR ITS SUPPLIERS BE LIABLE FOR ANY INDIRECT, SPECIAL, CONSEQUENTIAL, OR INCIDENTAL DAMAGES, INCLUDING, WITHOUT LIMITATION, LOST PROFITS OR LOSS OR DAMAGE TO DATA ARISING OUT OF THE USE OR INABILITY TO USE THIS MANUAL, EVEN IF CISCO OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.

Cisco and the Cisco Logo are trademarks of Cisco Systems, Inc. and/or its affiliates in the U.S. and other countries. A listing of Cisco's trademarks can be found at www.cisco.com/go/trademarks . Third party trademarks mentioned are the property of their respective owners. The use of the word partner does not imply a partnership relationship between Cisco and any other company. (1005R)

Any Internet Protocol (IP) addresses used in this document are not intended to be actual addresses. Any examples, command display output, and figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses in illustrative content is unintentional and coincidental.

Cisco Nexus 7000 Series NX-OS System Management Configuration Guide, Release 5.x

©2008–2011 Cisco Systems, Inc. All rights reserved.

Configuring Advanced BGP

This chapter describes how to configure advanced features of the Border Gateway Protocol (BGP) on the Cisco NX-OS device.

This chapter includes the following sections:

- Information About Advanced BGP

- Licensing Requirements for Advanced BGP

- Prerequisites for Advanced BGP

- Guidelines and Limitations for Advanced BGP

- Default Settings

- Configuring Advanced BGP

- Verifying the Advanced BGP Configuration

- Related Topics

- Additional References

- Feature History for BGP

Information About Advanced BGP

BGP is an interdomain routing protocol that provides loop-free routing between organizations or autonomous systems. Cisco NX-OS supports BGP version 4. BGP version 4 includes multiprotocol extensions that allow BGP to carry routing information for IP multicast routes and multiple Layer 3 protocol address families. BGP uses TCP as a reliable transport protocol to create TCP sessions with other BGP-enabled devices called BGP peers. When connecting to an external organization, the router creates external BGP (eBGP) peering sessions. BGP peers within the same organization exchange routing information through internal BGP (iBGP) peering sessions.

This section includes the following topics:

- Peer Templates

- Authentication

- Route Policies and Resetting BGP Sessions

- eBGP

- iBGP

- Capabilities Negotiation

- Route Dampening

- Load Sharing and Multipath

- Route Aggregation

- BGP Conditional Advertisement

- BGP Next-Hop Address Tracking

- Route Redistribution

- BFD

- Tuning BGP

- Multiprotocol BGP

- Graceful Restart and High Availability

- ISSU

- Virtualization Support

Peer Templates

BGP peer templates allow you to create blocks of common configuration that you can reuse across similar BGP peers. Each block allows you to define a set of attributes that a peer then inherits. You can choose to override some of the inherited attributes as well, making it a very flexible scheme for simplifying the repetitive nature of BGP configurations.

Cisco NX-OS implements three types of peer templates:

- The peer-session template defines BGP peer session attributes, such as the transport details, remote autonomous system number of the peer, and session timers. A peer-session template can also inherit attributes from another peer-session template (with locally defined attributes that override the attributes from an inherited peer-session).

- A peer-policy template defines the address-family dependent policy aspects for a peer including the inbound and outbound policy, filter-lists, and prefix-lists. A peer-policy template can inherit from a set of peer-policy templates. Cisco NX-OS evaluates these peer-policy templates in the order specified by the preference value in the inherit configuration. The lowest number is preferred over higher numbers.

- The peer template can inherit the peer-session and peer-policy templates to allow for simplified peer definitions. It is not mandatory to use a peer template but it can simplify the BGP configuration by providing reusable blocks of configuration.

Authentication

You can configure authentication for a BGP neighbor session. This authentication method adds an MD5 authentication digest to each TCP segment sent to the neighbor to protect BGP against unauthorized messages and TCP security attacks.

Note The MD5 password must be identical between BGP peers.

Route Policies and Resetting BGP Sessions

You can associate a route policy to a BGP peer. Route policies use route maps to control or modify the routes that BGP recognizes. You can configure a route policy for inbound or outbound route updates. The route policies can match on different criteria, such as a prefix or AS_path attribute, and selectively accept or deny the routes. Route policies can also modify the path attributes. See Chapter 17, “Configuring Policy-Based Routing” for more information on route polices.

When you change a route policy applied to a BGP peer, you must reset the BGP sessions for that peer. Cisco NX-OS supports the following three mechanisms to reset BGP peering sessions:

- Hard reset—A hard reset tears down the specified peering sessions, including the TCP connection, and deletes routes coming from the specified peer. This option interrupts packet flow through the BGP network. Hard reset is disabled by default.

- Soft reconfiguration inbound—A soft reconfiguration inbound triggers routing updates for the specified peer without resetting the session. You can use this option if you change an inbound route policy. Soft reconfiguration inbound saves a copy of all routes received from the peer before processing the routes through the inbound route policy. If you change the inbound route policy, Cisco NX-OS passes these stored routes through the modified inbound route policy to update the route table without tearing down existing peering sessions. Soft reconfiguration inbound can use significant memory resources to store the unfiltered BGP routes. Soft reconfiguration inbound is disabled by default.

- Route Refresh—A route refresh updates the inbound routing tables dynamically by sending route refresh requests to supporting peers when you change an inbound route policy. The remote BGP peer responds with a new copy of its routes that the local BGP speaker processes with the modified route policy. Cisco NX-OS automatically sends an outbound route refresh of prefixes to the peer.

- BGP peers advertise the route refresh capability as part of the BGP capability negotiation when establishing the BGP peer session. Route refresh is the preferred option and enabled by default.

Note BGP also uses route maps for route redistribution, route aggregation, route dampening, and other features. See “Configuring Route Policy Manager,” for more information on route maps.

eBGP

External BGP (eBGP) allows you to connect BGP peers from different autonomous systems to exchange routing updates. Connecting to external networks enables traffic from your network to be forwarded to other networks and across the Internet.

You should use loopback interfaces for establishing eBGP peering sessions because loopback interfaces are less susceptible to interface flapping. An interface flap occurs when the interface is administratively brought up or down because of a failure or maintenance issue. See the “Configuring eBGP” section for information on multihop, fast external failovers, and limiting the size of the AS-path attribute.

iBGP

Internal BGP (iBGP) allows you to connect BGP peers within the same autonomous system. You can use iBGP for multihomed BGP networks (networks that have more than one connection to the same external autonomous system).

Figure 11-1 shows an iBGP network within a larger BGP network.

Figure 11-1 iBGP Network

iBGP networks are fully meshed. Each iBGP peer has a direct connection to all other iBGP peers to prevent network loops.

For single-hop iBGP peers with update-source configured under neighbor configuration mode, the peer supports fast external fall-over.

Note You should configure a separate interior gateway protocol in the iBGP network.

This section includes the following topics:

- AS Confederations

- Route Reflector

AS Confederations

A fully meshed iBGP network becomes complex as the number of iBGP peers grows. You can reduce the iBGP mesh by dividing the autonomous system into multiple subautonomous systems and grouping them into a single confederation. A confederation is a group of iBGP peers that use the same autonomous system number to communicate to external networks. Each subautonomous system is fully meshed within itself and has a few connections to other subautonomous systems in the same confederation.

Figure 11-2 shows the BGP network from Figure 11-1, split into two subautonomous systems and one confederation.

Figure 11-2 AS Confederation

In this example, AS10 is split into two subautonomous systems, AS1 and AS2. Each subautonomous system is fully meshed, but there is only one link between the subautonomous systems. By using AS confederations, you can reduce the number of links compared to the fully meshed autonomous system in Figure 11-1.

Route Reflector

You can alternately reduce the iBGP mesh by using a route reflector configuration where route reflectors pass learned routes to neighbors so that all iBGP peers do not need to be fully meshed.

Figure 11-1 shows a simple iBGP configuration with four meshed iBGP speakers (routers A, B, C, and D). Without route reflectors, when router A receives a route from an external neighbor, it advertises the route to all three iBGP neighbors.

When you configure an iBGP peer to be a route reflector, it becomes responsible for passing iBGP learned routes to a set of iBGP neighbors.

In Figure 11-3, router B is the route reflector. When the route reflector receives routes advertised from router A, it advertises (reflects) the routes to routers C and D. Router A no longer has to advertise to both routers C and D.

Figure 11-3 Route Reflector

The route reflector and its client peers form a cluster. You do not have to configure all iBGP peers to act as client peers of the route reflector. You must configure any nonclient peer as fully meshed to guarantee that complete BGP updates reach all peers.

Capabilities Negotiation

A BGP speaker can learn about BGP extensions that are supported by a peer by using the capabilities negotiation feature. Capabilities negotiation allows BGP to use only the set of features supported by both BGP peers on a link.

If a BGP peer does not support capabilities negotiation, Cisco NX-OS attempts a new session to the peer without capabilities negotiation if you have configured the address family as IPv4. Any other multiprotocol configuration (such as IPv6) requires capabilities negotiation.

Route Dampening

Route dampening is a BGP feature that minimizes the propagation of flapping routes across an internetwork. A route flaps when it alternates between the available and unavailable states in rapid succession.

For example, consider a network with three BGP autonomous systems: AS1, AS2, and AS3. Suppose that a route in AS1 flaps (it becomes unavailable). Without route dampening, AS1 sends a withdraw message to AS2. AS2 propagates the withdrawal message to AS3. When the flapping route reappears, AS1 sends an advertisement message to AS2, which sends the advertisement to AS3. If the route repeatedly becomes unavailable, and then available, AS1 sends many withdrawal and advertisement messages that propagate through the other autonomous systems.

Route dampening can minimize flapping. Suppose that the route flaps. AS2 (in which route dampening is enabled) assigns the route a penalty of 1000. AS2 continues to advertise the status of the route to neighbors. Each time that the route flaps, AS2 adds to the penalty value. When the route flaps so often that the penalty exceeds a configurable suppression limit, AS2 stops advertising the route, regardless of how many times that it flaps. The route is now dampened.

The penalty placed on the route decays until the reuse limit is reached. At that time, AS2 advertises the route again. When the reuse limit is at 50 percent, AS2 removes the dampening information for the route.

Note The router does not apply a penalty to a resetting BGP peer when route dampening is enabled, even though the peer reset withdraws the route.

Load Sharing and Multipath

BGP can install multiple equal-cost eBGP or iBGP paths into the routing table to reach the same destination prefix. Traffic to the destination prefix is then shared across all the installed paths.

The BGP best-path algorithm considers the paths as equal-cost paths if the following attributes are identical:

- Weight

- Local preference

- AS_path

- Origin code

- Multi-exit discriminator (MED)

- IGP cost to the BGP next hop

BGP selects only one of these multiple paths as the best path and advertises the path to the BGP peers.

Note Paths that are received from different AS confederations are considered as equal-cost paths if the external AS_path values and the other attributes are identical.

Note When you configure a route reflector for iBGP multipath, and the route reflector advertises the selected best path to its peers, the next hop for the path is not modified.

Route Aggregation

You can configure aggregate addresses. Route aggregation simplifies route tables by replacing a number of more specific addresses with an address that represents all the specific addresses. For example, you can replace these three more specific addresses, 10.1.1.0/24, 10.1.2.0/24, and 10.1.3.0/24 with one aggregate address, 10.1.0.0/16.

Aggregate prefixes are present in the BGP route table so that fewer routes are advertised.

Note Cisco NX-OS does not support automatic route aggregation.

Route aggregation can lead to forwarding loops. To avoid this problem, when BGP generates an advertisement for an aggregate address, it automatically installs a summary discard route for that aggregate address in the local routing table. BGP sets the administrative distance of the summary discard to 220 and sets the route type to discard. BGP does not use discard routes for next-hop resolution.

BGP Conditional Advertisement

BGP conditional advertisement allows you to configure BGP to advertise or withdraw a route based on whether or not a prefix exists in the BGP table. This feature is useful, for example, in multihomed networks, in which you want BGP to advertise some prefixes to one of the providers only if information from the other provider is not present.

Consider an example network with three BGP autonomous systems: AS1, AS2, and AS3, where AS1 and AS3 connect to the Internet and to AS2. Without conditional advertisement, AS2 propagates all routes to both AS1 and AS3. With conditional advertisement, you can configure AS2 to advertise certain routes to AS3 only if routes from AS1 do not exist (if for example, the link to AS1 fails).

BGP conditional advertisement adds an exist or not-exist test to each route that matches the configured route map. See the “Configuring BGP Conditional Advertisement” section for more information.

BGP Next-Hop Address Tracking

BGP monitors the next-hop address of installed routes to verify next-hop reachability and to select, install, and validate the BGP best path. BGP next-hop address tracking speeds up this next-hop reachability test by triggering the verification process when routes change in the Routing Information Base (RIB) that may affect BGP next-hop reachability.

BGP receives notifications from the RIB when the next-hop information changes (event-driven notifications). BGP is notified when any of the following events occurs:

- The next hop becomes unreachable.

- The next hop becomes reachable.

- The fully recursed Interior Gateway Protocol (IGP) metric to the next hop changes.

- The first hop IP address or first hop interface changes.

- The next hop becomes connected.

- The next hop becomes unconnected.

- The next hop becomes a local address.

- The next hop becomes a nonlocal address.

Note Reachability and recursed metric events trigger a best-path recalculation.

Event notifications from the RIB are classified as critical and noncritical. Notifications for critical and noncritical events are sent in separate batches. However, a noncritical event is sent with the critical events if the noncritical event is pending and there is a request to read the critical events.

- Critical events are related to next-hop reachability, such as the loss of next hops resulting in a switchover to a different path. A change in the IGP metric for a next hop resulting in a switchover to a different path can also be considered a critical event.

- Non-critical events are related to next hops being added without affecting the best path or changing the IGP metric to a single next hop.

See the “Configuring BGP Next-Hop Address Tracking” section for more information.

Note Critical and non-critical events can be configured individually on a per address family basis. For more information on address families, see the “Configuring MPLS Layer 3 VPNs” chapter in the Cisco Nexus 7000 Series NX-OS MPLS Configuration Guide.

Route Redistribution

You can configure BGP to redistribute static routes or routes from other protocols. You must configure a route map with the redistribution to control which routes are passed into BGP. A route map allows you to filter routes based on attributes such as the destination, origination protocol, route type, route tag, and so on. See “Configuring Route Policy Manager,” for more information.

Prior to Cisco NX-OS Release 5.2(1), when you redistribute BGP to IGP, iBGP is redistributed as well. To override this behavior, you must insert an additional deny statement into the route map. Beginning with Cisco NX-OS Release 5.2(1), redistribution varies as follows:

- In a non-MPLS VPN scenario, iBGP is not redistributed to IGP by default.

- In an MPLS VPN scenario (route distinguisher configured under a VRF), iBGP is redistributed to IGP by default.

You can use route maps to override the default behavior in both scenarios, but be careful when doing so as incorrect use of route maps can result in network loops. The following examples show how to use route maps to change the default behavior.

You can chnage the default behavior for scenario 1 by modifying the route map as follows:

route-map foo permit 10

match route-type internal

router ospf 1

redistribute bgp 100 route-map foo

Similarly, you can change the default behavior for scenario 2 by modifying the route map as follows:

route-map foo deny 10

match route-type internal

router ospf 1

vrf bar

redistribute bgp 100 route-map foo

BFD

This feature supports bidirectional forwarding detection (BFD) for IPv4 only. BFD is a detection protocol designed to provide fast forwarding-path failure detection times. BFD provides subsecond failure detection between two adjacent devices and can be less CPU-intensive than protocol hello messages because some of the BFD load can be distributed onto the data plane on supported modules.

BFD for BGP is supported on eBGP peers and iBGP single-hop peers. Configure the update-source option in neighbor configuration mode for iBGP single-hop peers using BFD.

Note BFD is not supported on other iBGP peers or for multihop eBGP peers.

See the Cisco Nexus 7000 Series NX-OS Interfaces Configuration Guide, Release 5.x, for more information.

Tuning BGP

You can modify the default behavior of BGP through BGP timers and by adjusting the best-path algorithm.

This section includes the following topics:

- BGP Timers

- Tuning the Best-Path Algorithm

BGP Timers

BGP uses different types of timers for neighbor session and global protocol events. Each established session has a minimum of two timers for sending periodic keepalive messages and for timing out sessions when peer keepalives do not arrive within the expected time. In addition, there are other timers for handling specific features. Typically, you configure these timers in seconds. The timers include a random adjustment so that the same timers on different BGP peers trigger at different times.

Tuning the Best-Path Algorithm

You can modify the default behavior of the best-path algorithm through optional configuration parameters, including changing how the algorithm handles the multi-exit discriminator (MED) attribute and the router ID.

Multiprotocol BGP

BGP on Cisco NX-OS supports multiple address families. Multiprotocol BGP (MP-BGP) carries different sets of routes depending on the address family. For example, BGP can carry one set of routes for IPv4 unicast routing, one set of routes for IPv4 multicast routing, and one set of routes for IPv6 multicast routing. You can use MP-BGP for reverse-path forwarding (RPF) checks in IP multicast networks.

Note Because Multicast BGP does not propagate multicast state information, you need a multicast protocol, such as Protocol Independent Multicast (PIM).

Use the router address-family and neighbor address-family configuration modes to support multiprotocol BGP configurations. MP-BGP maintains separate RIBs for each configured address family, such as a unicast RIB and a multicast RIB for BGP.

A multiprotocol BGP network is backward compatible but BGP peers that do not support multiprotocol extensions cannot forward routing information, such as address family identifier information, that the multiprotocol extensions carry.

Graceful Restart and High Availability

Cisco NX-OS supports nonstop forwarding and graceful restart for BGP.

You can use nonstop forwarding (NSF) for BGP to forward data packets along known routes in the Forward Information Base (FIB) while the BGP routing protocol information is being restored following a failover. With NSF, BGP peers do not experience routing flaps. During a failover, the data traffic is forwarded through intelligent modules while the standby supervisor becomes active.

If a Cisco NX-OS router experiences a cold reboot, the network does not forward traffic to the router and removes the router from the network topology. In this scenario, BGP experiences a nongraceful restart and removes all routes. When Cisco NX-OS applies the startup configuration, BGP reestablishes peering sessions and relearns the routes.

A Cisco NX-OS router that has dual supervisors can experience a stateful supervisor switchover. During the switchover, BGP uses nonstop forwarding to forward traffic based on the information in the FIB, and the system is not removed from the network topology. A router whose neighbor is restarting is referred to as a “helper.” After the switchover, a graceful restart operation begins. When it is in progress, both routers reestablish their neighbor relationship and exchange their BGP routes. The helper continues to forward prefixes pointing to the restarting peer, and the restarting router continues to forward traffic to peers even though those neighbor relationships are restarting. When the restarting router has all route updates from all BGP peers that are graceful restart capable, the graceful restart is complete, and BGP informs the neighbors that it is operational again.

For single-hop iBGP peers with update-source configured under neighbor configuration mode, the peer supports fast external fall-over.

Low Memory Handling

BGP reacts to low memory for the following conditions:

- Minor alert—BGP does not establish any new eBGP peers. BGP continues to establish new iBGP peers and confederate peers. Established peers remain, but reset peers are not re-established.

- Severe alert—BGP shuts down select established eBGP peers every two minutes until the memory alert becomes minor. For each eBGP peer, BGP calculates the ratio of total number of paths received to the number of paths selected as best paths. The peers with the highest ratio are selected to be shut down to reduce memory usage. You must clear a shutdown eBGP peer before you can bring the eBGP peer back up to avoid oscillation.

Note You can exempt important eBGP peers from this selection process.

- Critical alert—BGP gracefully shuts down all the established peers. You must clear a shutdown BGP peer before you can bring the BGP peer back up.

See the “Tuning BGP” section for more information on how to exempt a BGP peer from a shutdown due to a low memory condition.

ISSU

Cisco NX-OS supports in-service software upgrades (ISSU). ISSU allows you to upgrade software without impacting forwarding.

The following conditions are required to support ISSU:

- Graceful restart must be enabled (default)

- Keepalive and hold timers must not be smaller than their default values

If either of these requirements is not met, Cisco NX-OS issues a warning. You can proceed with the upgrade or downgrade, but service might be disrupted.

Note Cisco NX-OS cannot guarantee ISSU for non-default timer values if the negotiated hold time between BGP peers is less than the system switchover time.

Virtualization Support

Cisco NX-OS supports multiple instances of BGP that run on the same system. BGP supports virtual routing and forwarding (VRF) instances that exist within virtual device contexts (VDCs). You can configure one BGP instance in a VDC, but you can have multiple VDCs on the system.

By default, Cisco NX-OS places you in the default VDC and default VRF unless you specifically configure another VDC and VRF. See the Cisco NX-OS Virtual Device Context Configuration Guide and Chapter14, “Configuring Layer 3 Virtualization”

Licensing Requirements for Advanced BGP

Product

License Requirement

Cisco NX-OS

BGP requires an Enterprise Services license. For a complete explanation of the Cisco NX-OS licensing scheme and how to obtain and apply licenses, see the Cisco NX-OS Licensing Guide.

Prerequisites for Advanced BGP

Advanced BGP has the following prerequisites:

- You must enable BGP (see the “Enabling BGP” section).

- You should have a valid router ID configured on the system.

- You must have an AS number, either assigned by a Regional Internet Registry (RIR) or locally administered.

- You must have reachability (such as an interior gateway protocol [IGP], a static route, or a direct connection) to the peer that you are trying to make a neighbor relationship with.

- You must explicitly configure an address family under a neighbor for the BGP session establishment.

Guidelines and Limitations for Advanced BGP

Advanced BGP has the following configuration guidelines and limitations:

- The dynamic AS number prefix peer configuration overrides the individual AS number configuration inherited from a BGP template.

- If you configure a dynamic AS number for prefix peers in an AS confederation, BGP establishes sessions with only the AS numbers in the local confederation.

- BGP sessions created through a dynamic AS number prefix peer ignore any configured eBGP multihop time-to-live (TTL) value or a disabled check for directly connected peers.

- Configure a router ID for BGP to avoid automatic router ID changes and session flaps.

- Use the maximum-prefix configuration option per peer to restrict the number of routes received and system resources used.

- Configure the update source to establish a session with eBGP multihop sessions.

- Specify a BGP route map if you configure a redistribution.

- Configure the BGP router ID within a VRF.

- If you decrease the keepalive and hold timer values, the network might experience session flaps.

- If you configure VDCs, install the Advanced Services license and enter the desired VDC (see the Cisco Nexus 7000 Series NX-OS Virtual Device Context Configuration Guide, Release 5.x ).

- When you redistribute BGP to IGP, iBGP is redistributed as well. To override this behavior, you must insert an additional deny statement into the route map.

- Cisco NX-OS does not support multi-hop BFD. BFD for BGP has the following limitations:

– BFD is supported only for BGP IPv4.

– BFD is supported only for eBGP peers and iBGP single-hop peers.

– To enable BFD for iBGP single-hop peers, you must configure the update-source option on the physical interface.

– BFD is not supported for multi-hop iBGP peers and multi-hop eBGP peers.

- For single-hop iBGP peers with update-source configured under neighbor configuration mode, the peer supports fast external fall-over.

- The following guidelines and limitations apply to the remove-private-as command:

– It applies only to eBGP peers.

– It can be configured only in neighbor configuration mode and not in neighbor-address-family mode.

– If the AS-path includes both private and public AS numbers, the private AS numbers are not removed.

– If the AS-path contains the AS number of the eBGP neighbor, the private AS numbers are not removed.

– Private AS numbers are removed only if all AS numbers in that AS-path belong to a private AS number range. Private AS numbers are not removed if a peer’s AS number or a non-private AS number is found in the AS-path segment.

Default Settings

Table 11-1 Default BGP Parameters

Parameters

Default

BGP feature

Disabled

Keep alive interval

60 seconds

Hold timer

180 seconds

Dynamic capability

Enabled

Configuring Advanced BGP

This section includes the following topics:

- Configuring BGP Session Templates

- Configuring BGP Peer-Policy Templates

- Configuring BGP Peer Templates

- Configuring Prefix Peering

- Configuring BGP Authentication

- Resetting a BGP Session

- Modifying the Next-Hop Address

- Configuring BGP Next-Hop Address Tracking

- Configuring Next-Hop Filtering

- Disabling Capabilities Negotiation

- Configuring eBGP

- Configuring AS Confederations

- Configuring Route Reflector

- Configuring Route Dampening

- Configuring Load Sharing and ECMP

- Configuring Maximum Prefixes

- Configuring Dynamic Capability

- Configuring Aggregate Addresses

- Configuring BGP Conditional Advertisement

- Configuring Route Redistribution

- Configuring Multiprotocol BGP

- Tuning BGP

- Configuring a Graceful Restart

- Configuring Virtualization

Note If you are familiar with the Cisco IOS CLI, be aware that the Cisco NX-OS commands for this feature might differ from the Cisco IOS commands that you would use.

Configuring BGP Session Templates

You can use BGP session templates to simplify the BGP configuration for multiple BGP peers with similar configuration needs. BGP templates allow you to reuse common configuration blocks. You configure BGP templates first and then apply these templates to BGP peers.

With BGP session templates, you can configure session attributes such as inheritance, passwords, timers, and security.

A peer-session template can inherit from one other peer-session template. You can configure the second template to inherit from a third template. The first template also inherits this third template. This indirect inheritance can continue for up to seven peer-session templates.

Any attributes configured for the neighbor take priority over any attributes inherited by that neighbor from a BGP template.

BEFORE YOU BEGIN

You must enable BGP (see the “Enabling BGP” section).

Ensure that you are in the correct VDC (or use the switchto vdc command).

Note When editing a template, you can use the no form of a command at either the peer or template level to explicitly override a setting in a template. You must use the default form of the command to reset that attribute to the default state.

SUMMARY STEPS

1. configure terminal

2. router bgp autonomous-system-number

3. template peer-session template-name

4. (Optional) password number password

5. (Optional) timers keepalive hold

6. exit

7. neighbor ip-address remote-as as-number

8. inherit peer-session template-name

9. (Optional) description text

10. (Optional) show bgp peer-session template-name

11. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

router bgp autonomous-system-number

Example:

switch(config)# router bgp 65536

switch(config-router)#

Step 3

template peer-session template-name

Example:

switch(config-router)# template peer-session BaseSession

switch(config-router-stmp)#

Step 4

password number password

Example:

switch(config-router-stmp)# password 0 test

(Optional) Adds the clear text password test to the neighbor. The password is stored and displayed in type 3 encrypted form (3DES).

Step 5

timers keepalive hold

Example:

switch(config-router-stmp)# timers 30 90

(Optional) Adds the BGP keepalive and holdtimer values to the peer-session template.

The default keepalive interval is 60. The default hold time is 180.

Step 6

exit

Example:

switch(config-router-stmp)# exit

switch(config-router)#

Exits peer-session template configuration mode.

Step 7

neighbor ip-address remote-as as-number

Example:

switch(config-router)# neighbor 192.168.1.2 remote-as 65536

switch(config-router-neighbor)#

Places the router in the neighbor configuration mode for BGP routing and configures the neighbor IP address.

Step 8

inherit peer-session template-name

Example:

switch(config-router-neighbor)# inherit peer-session BaseSession

switch(config-router-neighbor)

Applies a peer-session template to the peer.

Step 9

description text

Example:

switch(config-router-neighbor)# description Peer Router A

switch(config-router-neighbor)

(Optional) Adds a description for the neighbor.

Step 10

show bgp peer-session template-name

Example:

switch(config-router-neighbor)# show bgp peer-session BaseSession

(Optional) Displays the peer-policy template.

Step 11

copy running-config startup-config

Example:

switch(config-router-neighbor)# copy running-config startup-config

(Optional) Saves this configuration change.

Use the show bgp neighbor command to see the template applied. See the Cisco Nexus 7000 Series NX-OS Unicast Routing Command Reference, Release 5.x, for details on all commands available in the template.

This example shows how to configure a BGP peer-session template and apply it to a BGP peer:

switch# configure terminal

switch(config)# router bgp 65536

switch(config-router)# template peer-session BaseSession

switch(config-router-stmp)# timers 30 90

switch(config-router-stmp)# exit

switch(config-router)# neighbor 192.168.1.2 remote-as 65536

switch(config-router-neighbor)# inherit peer-session BaseSession

switch(config-router-neighbor)# description Peer Router A

switch(config-router-neighbor)# address-family ipv4 unicast

switch(config-router-neighbor)# copy running-config startup-config

Configuring BGP Peer-Policy Templates

You can configure a peer-policy template to define attributes for a particular address family. You assign a preference to each peer-policy template and these templates are inherited in the order specified, for up to five peer-policy templates in a neighbor address family.

Cisco NX-OS evaluates multiple peer policies for an address family using the preference value. The lowest preference value is evaluated first. Any attributes configured for the neighbor take priority over any attributes inherited by that neighbor from a BGP template.

Peer-policy templates can configure address family-specific attributes such as AS-path filter lists, prefix lists, route reflection, and soft reconfiguration.

BEFORE YOU BEGIN

You must enable BGP (see the “Enabling BGP” section).

Ensure that you are in the correct VDC (or use the switchto vdc command).

Note When editing a template, you can use the no form of a command at either the peer or template level to explicitly override a setting in a template. You must use the default form of the command to reset that attribute to the default state.

SUMMARY STEPS

1. configure terminal

2. router bgp autonomous-system-number

3. template peer-policy template-name

4. (Optional) advertise-active-only

5. (Optional) maximum-prefix number

6. exit

7. neighbor ip-address remote-as as-number

8. address-family {ipv4 | ipv6 | vpnv4 | vpnv6} {multicast | unicast}

9. inherit peer-policy template-name preference

10. (Optional) show bgp peer-policy template-name

11. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

router bgp autonomous-system-number

Example:

switch(config)# router bgp 65536

switch(config-router)#

Step 3

template peer-policy template-name

Example:

switch(config-router)# template peer-policy BasePolicy

switch(config-router-ptmp)#

Creates a peer-policy template.

Step 4

advertise-active-only

Example:

switch(config-router-ptmp)# advertise-active-only

(Optional) Advertises only active routes to the peer.

Step 5

maximum-prefix number

Example:

switch(config-router-ptmp)# maximum-prefix 20

(Optional) Sets the maximum number of prefixes allowed from this peer.

Step 6

exit

Example:

switch(config-router-ptmp)# exit

switch(config-router)#

Exits peer-policy template configuration mode.

Step 7

neighbor ip-address remote-as as-number

Example:

switch(config-router)# neighbor 192.168.1.2 remote-as 65536

switch(config-router-neighbor)#

Step 8

address-family {ipv4 | ipv6 | vpnv4 | vpnv6}{multicast | unicast}

Example:

switch(config-router-neighbor)# address-family ipv4 unicast

switch(config-router-neighbor-af)#

Enters global address family configuration mode for the IPv4 address family.

Step 9

inherit peer-policy template-name preference

Example:

switch(config-router-neighbor-af)# inherit peer-policy BasePolicy 1

Applies a peer-policy template to the peer address family configuration and assigns the preference value for this peer policy.

Step 10

show bgp peer-policy template-name

Example:

switch(config-router-neighbor-af)# show bgp peer-policy BasePolicy

(Optional) Displays the peer-policy template.

Step 11

copy running-config startup-config

Example:

switch(config-router-neighbor-af)# copy running-config startup-config

(Optional) Saves this configuration change.

Use the show bgp neighbor command to see the template applied. See the Cisco Nexus 7000 Series NX-OS Unicast Routing Command Reference, Release 5.x, for details on all commands available in the template.

This example shows how to configure a BGP peer-session template and apply it to a BGP peer:

This example shows how to configure a BGP peer-policy template and apply it to a BGP peer:

switch# configure terminal

switch(config)# router bgp 65536

switch(config-router)# template peer-session BasePolicy

switch(config-router-ptmp)# maximum-prefix 20

switch(config-router-ptmp)# exit

switch(config-router)# neighbor 192.168.1.1 remote-as 65536

switch(config-router-neighbor)# address-family ipv4 unicast

switch(config-router-neighbor-af)# inherit peer-policy BasePolicy

switch(config-router-neighbor-af)# copy running-config startup-config

Configuring BGP Peer Templates

You can configure BGP peer templates to combine session and policy attributes in one reusable configuration block. Peer templates can also inherit peer-session or peer-policy templates. Any attributes configured for the neighbor take priority over any attributes inherited by that neighbor from a BGP template. You configure only one peer template for a neighbor, but that peer template can inherit peer-session and peer-policy templates.

Peer templates support session and address family attributes, such as eBGP multihop time-to-live, maximum prefix, next-hop self, and timers.

BEFORE YOU BEGIN

You must enable BGP (see the “Enabling BGP” section).

Ensure that you are in the correct VDC (or use the switchto vdc command).

Note When editing a template, you can use the no form of a command at either the peer or template level to explicitly override a setting in a template. You must use the default form of the command to reset that attribute to the default state.

SUMMARY STEPS

1. configure terminal

2. router bgp autonomous-system-number

3. template peer template-name

4. inherit peer-session template-name

5. address-family {ipv4 | ipv6 | vpnv4 | vpnv6}{multicast | unicast}

6. inherit peer template-name

7. exit

8. timers keepalive hold

9. exit

10. neighbor ip-address remote-as as-number

11. inherit peer template-name

12. timers keepalive hold

13. (Optional) show bgp peer-template template-name

14. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

router bgp autonomous-system-number

Example:

switch(config)# router bgp 65536

Enters BGP mode and assigns the autonomous system number to the local BGP speaker.

Step 3

template peer template-name

Example:

switch(config-router)# template peer BasePeer

switch(config-router-neighbor)#

Step 4

inherit peer-session template-name

Example:

switch(config-router-neighbor)# inherit peer-session BaseSession

(Optional) Inherits a peer-session template in the peer template.

Step 5

address-family {ipv4 | ipv6 | vpnv4 | vpnv6}{multicast | unicast}

Example:

switch(config-router-neighbor)# address-family ipv4 unicast

switch(config-router-neighbor-af)#

(Optional) Configures the global address family configuration mode for the IPv4 address family.

Step 6

inherit peer template-name

Example:

switch(config-router-neighbor-af)# inherit peer BasePolicy

(Optional) Applies a peer template to the neighbor address family configuration.

Step 7

exit

Example:

switch(config-router-neighbor-af)# exit

switch(config-router-neighbor)#

Exits BGP neighbor address family configuration mode.

Step 8

timers keepalive hold

Example:

switch(config-router-neighbor)# timers 45 100

(Optional) Adds the BGP timer values to the peer.

These values override the timer values in the peer-session template, BaseSession.

Step 9

exit

Example:

switch(config-router-neighbor)# exit

switch(config-router)#

Exits BGP peer template configuration mode.

Step 10

neighbor ip-address remote-as as-number

Example:

switch(config-router)# neighbor 192.168.1.2 remote-as 65536

switch(config-router-neighbor)#

Step 11

inherit peer template-name

Example:

switch(config-router-neighbor)# inherit peer BasePeer

Inherits the peer template.

Step 12

timers keepalive hold

Example:

switch(config-router-neighbor)# timers 60 120

(Optional) Adds the BGP timer values to this neighbor.

These values override the timer values in the peer template and the peer-session template.

Step 13

show bgp peer-template template-name

Example:

switch(config-router-neighbor-af)# show bgp peer-template BasePeer

(Optional) Displays the peer template.

Step 14

copy running-config startup-config

Example:

switch(config-router-neighbor-af)# copy running-config startup-config

(Optional) Saves this configuration change.

Use the show bgp neighbor command to see the template applied. See the Cisco Nexus 7000 Series NX-OS Unicast Routing Command Reference, Release 5.x, for details on all commands available in the template.

This example shows how to configure a BGP peer template and apply it to a BGP peer:

switch# configure terminal

switch(config)# router bgp 65536

switch(config-router)# template peer BasePeer

switch(config-router-neighbor)# inherit peer-session BaseSession

switch(config-router-neighbor)# address-family ipv4 unicast

switch(config-router-neighbor-af)# inherit peer-policy BasePolicy 1

switch(config-router-neighbor-af)# exit

switch(config-router-neighbor)# exit

switch(config-router)# neighbor 192.168.1.2 remote-as 65536

switch(config-router-neighbor)# inherit peer BasePeer

switch(config-router-neighbor)# copy running-config startup-config

Configuring Prefix Peering

BGP supports the definition of a set of peers using a prefix for both IPv4 and IPv6. This feature allows you to not have to add each neighbor to the configuration.

When defining a prefix peering, you must specify the remote AS number with the prefix. BGP accepts any peer that connects from that prefix and autonomous system if the prefix peering does not exceed the configured maximum peers allowed.

When a BGP peer that is part of a prefix peering disconnects, Cisco NX-OS holds its peer structures for a defined prefix peer timeout value. An established peer can reset and reconnect without danger of being blocked because other peers have consumed all slots for that prefix peering.

To configure the BGP prefix peering timeout value, use the following command in router configuration mode:

Command

Purpose

timers prefix-peer-timeout value

Example:

switch(config-router-neighbor)# timers prefix-peer-timeout 120

Configures the timeout value for prefix peering. The range is from 0 to 1200 seconds. The default value is 30.

To configure the maximum number of peers, use the following command in neighbor configuration mode:

Command

Purpose

maximum-peers value

Example:

switch(config-router-neighbor)# maximum-peers 120

Configures the maximum number of peers for this prefix peering. The range is from 1 to 1000.

This example shows how to configure a prefix peering that accepts up to 10 peers:

switch(config)# router bgp 65536

switch(config-router)# timers prefix-peer-timeout 120

switch(config-router)# neighbor 10.100.200.0/24 remote-as 65536

switch(config-router-neighbor)# maximum-peers 10

switch(config-router-neighbor)# address-family ipv4 unicast

switch(config-router-neighbor-af)#

Use the show ip bgp neighbor command to show the details of the configuration for that prefix peering with a list of the currently accepted instances and the counts of active, maximum concurrent, and total accepted peers.

Configuring BGP Authentication

You can configure BGP to authenticate route updates from peers using MD5 digests.

To configure BGP to use MD5 authentication, use the following command in neighbor configuration mode:

Command

Purpose

password [0 | 3 | 7] string

Example:

switch(config-router-neighbor)# password BGPpassword

Configures an MD5 password for BGP neighbor sessions.

Resetting a BGP Session

If you modify a route policy for BGP, you must reset the associated BGP peer sessions. If the BGP peers do not support route refresh, you can configure a soft reconfiguration for inbound policy changes. Cisco NX-OS automatically attempts a soft reset for the session.

Command

Purpose

soft-reconfiguration inbound

Example:

switch(config-router-neighbor-af)# soft-reconfiguration inbound

Enables soft reconfiguration to store the inbound BGP route updates. This command triggers an automatic soft clear or refresh of BGP neighbor sessions.

To reset a BGP neighbor session, use the following command in any mode:

Command

Purpose

clear bgp {ipv4 | ipv6 | vpnv4 | vpnv6} {unicast | multicast} ip-address soft {in | out}

Example:

switch# clear bgp ip unicast 192.0.2.1 soft in

Resets the BGP session without tearing down the TCP session.

Modifying the Next-Hop Address

You can modify the next-hop address used in a route advertisement in the following ways:

- Disable next-hop calculation and use the local BGP speaker address as the next-hop address.

- Set the next-hop address as a third-party address. Use this feature in situations where the original next-hop address is on the same subnet as the peer that the route is being sent to. Using this feature saves an extra hop during forwarding.

Command

Purpose

next-hop-self

Example:

switch(config-router-neighbor-af)# next-hop-self

Uses the local BGP speaker address as the next-hop address in route updates. This command triggers an automatic soft clear or refresh of BGP neighbor sessions.

next-hop-third-party

Example:

switch(config-router-neighbor-af)# next-hop-third-party

Sets the next-hop address as a third-party address. Use this command for single-hop EBGP peers that do not have next-hop-self configured

Configuring BGP Next-Hop Address Tracking

BGP next-hop address tracking is enabled by default and cannot be disabled.

You can modify the delay interval between RIB checks to increase the performance of BGP next-hop tracking.

To modify the BGP next-hop address tracking, use the following commands in address-family configuration mode:

Command

Purpose

nexthop trigger-delay {critical | non-critical} milliseconds

Example:

switch(config-router-af)# nexthop trigger-delay critical 5000

Specifies the next-hop address tracking delay timer for critical next-hop reachability routes and for noncritical routes. The range is from 1 to 4294967295 milliseconds. The critical timer default is 3000. The noncritical timer default is 10000.

Configuring Next-Hop Filtering

BGP next-hop filtering allows you to specify that when a next-hop address is checked with the RIB, the underlying route for that next-hop address is passed through the route map. If the route map rejects the route, the next-hop address is treated as unreachable.

BGP marks all next hops that are rejected by the route policy as invalid and does not calculate the best path for the routes that use the invalid next-hop address.

To configure BGP next-hop filtering, use the following command in address-family configuration mode:

Command

Purpose

nexthop route-map name

Example:

switch(config-router-af)# nexthop route-map nextHopLimits

Specifies a route map to match the BGP next-hop route to. The name can be any case-sensitive, alphanumeric string up to 63 characters.

Disabling Capabilities Negotiation

You can disable capabilities negotiations to interoperate with older BGP peers that do not support capabilities negotiation.

Command

Purpose

dont-capability-negotiate

Example:

switch(config-router-neighbor)# dont-capability-negotiate

Disables capabilities negotiation. You must manually reset the BGP sessions after configuring this command.

Configuring eBGP

This section includes the following topics:

- Disabling eBGP Single-Hop Checking

- Configuring eBGP Multihop

- Disabling a Fast External Fallover

- Limiting the AS-path Attribute

- Configuring Local AS Support

Disabling eBGP Single-Hop Checking

You can configure eBGP to disable checking whether a single-hop eBGP peer is directly connected to the local router. Use this option for configuring a single-hop loopback eBGP session between directly connected switches.

To disable checking whether or not a single-hop eBGP peer is directly connected, use the following command in neighbor configuration mode:

Command

Purpose

disable-connected-check

Example:

switch(config-router-neighbor)# disable-connected-check

Disables checking whether or not a single-hop eBGP peer is directly connected. You must manually reset the BGP sessions after using this command.

Configuring eBGP Multihop

You can configure the eBGP time-to-live (TTL) value to support eBGP multihop. In some situations, an eBGP peer is not directly connected to another eBGP peer and requires multiple hops to reach the remote eBGP peer. You can configure the eBGP TTL value for a neighbor session to allow these multihop sessions.

Command

Purpose

ebgp-multihop ttl-value

Example:

switch(config-router-neighbor)# ebgp-multihop 5

Configures the eBGP TTL value for eBGP multihop. The range is from 2 to 255. You must manually reset the BGP sessions after using this command.

Disabling a Fast External Fallover

By default, the Cisco Nexus 7000 Series device supports fast external fallover for neighbors in all VRFs and address-families (IPv4 or IPv6). Typically, when a BGP router loses connectivity to a directly connected eBGP peer, BGP triggers a fast external fallover by resetting the eBGP session to the peer. You can disable this fast external fallover to limit the instability caused by link flaps.

Command

Purpose

no fast-external-fallover

Example:

switch(config-router)# no fast-external-fallover

Disables a fast external fallover for eBGP peers. This command is enabled by default.

Limiting the AS-path Attribute

You can configure eBGP to discard routes that have excessive AS numbers in the AS-path attribute.

Command

Purpose

maxas-limit number

Example:

switch(config-router)# maxas-limit 50

Discards eBGP routes that have a number of AS-path segments that exceed the specified limit. The range is from 1 to 2000.

Configuring Local AS Support

The local-AS feature allows a router to appear to be a member of a second autonomous system (AS), in addition to its real AS. Local AS allows two ISPs to merge without modifying peering arrangements. Routers in the merged ISP become members of the new autonomous system but continue to use their old AS numbers for their customers.

This feature can only be used for true eBGP peers. You cannot use this feature for two peers that are members of different confederation sub-autonomous systems.

To configure eBGP local AS support, use the following command in neighbor configuration mode:

Command

Purpose

local-as number [no-prepend [replace-as [dual-as]]]

Example:

switch(config-router-neighbor)# local-as 1.1

Configures eBGP to prepend the local AS number to the AS_PATH attribute.The AS number can be a 16-bit integer or a 32-bit integer in the form of a higher 16-bit decimal number and a lower 16-bit decimal number in xx.xx format.

This example shows how to configure local AS support on a VRF:

switch(config)# router bgp 1

switch(config-router)# vrf test

switch(config-router-vrf)# local-as 1

switch(config-router-vrf)# show running-config bgp

Configuring AS Confederations

To configure an AS confederation, you must specify a confederation identifier. To the outside world, the group of autonomous systems within the AS confederation look like a single autonomous system with the confederation identifier as the autonomous system number.

To configure a BGP confederation identifier, use the following command in router configuration mode:

Command

Purpose

confederation identifier as-number

Example:

switch(config-router)# confederation identifier 4000

Configures a confederation identifier for an AS confederation. This command triggers an automatic notification and session reset for the BGP neighbor sessions.

To configure the autonomous systems that belong to the AS confederation, use the following command in router configuration mode:

Command

Purpose

bgp confederation peers as-number [as-number2...]

Example:

switch(config-router)# bgp confederation peers 5 33 44

Specifies a list of autonomous systems that belong to the confederation. This command triggers an automatic notification and session reset for the BGP neighbor sessions.

Configuring Route Reflector

You can configure iBGP peers as route reflector clients to the local BGP speaker, which acts as the route reflector. Together, a route reflector and its clients form a cluster. A cluster of clients usually has a single route reflector. In such instances, the cluster is identified by the router ID of the route reflector. To increase redundancy and avoid a single point of failure in the network, you can configure a cluster with more than one route reflector. You must configure all route reflectors in the cluster with the same 4-byte cluster ID so that a route reflector can recognize updates from route reflectors in the same cluster.

BEFORE YOU BEGIN

You must enable BGP (see the “Enabling BGP” section).

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. router bgp as-number

3. cluster-id cluster-id

4. address-family {ipv4 | ipv6 | vpnv4 | vpnv6} {unicast | multicast}

5. (Optional) client-to-client reflection

6. exit

7. neighbor ip-address remote-as as-number

8. address-family {ipv4 | ipv6 | vpnv4 | vpnv6} {unicast | multicast}

9. route-reflector-client

10. (Optional) show bgp {ipv4 | ipv6 | vpnv4 | vpnv6} {unicast | multicast} neighbors

11. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

router bgp as-number

Example:

switch(config)# router bgp 65536

switch(config-router)#

Enters BGP mode and assigns the autonomous system number to the local BGP speaker.

Step 3

cluster-id cluster-id

Example:

switch(config-router)# cluster-id 192.0.2.1

Configures the local router as one of the route reflectors that serve the cluster. You specify a cluster ID to identify the cluster. This command triggers an automatic soft clear or refresh of BGP neighbor sessions.

Step 4

address-family {ipv4 | ipv6 | vpnv4 | vpnv6} {unicast | multicast}

Example:

switch(config-router)# address-family ipv4 unicast

switch(config-router-af)#

Enters router address family configuration mode for the specified address family.

Step 5

client-to-client reflection

Example:

switch(config-router-af)# client-to-client reflection

(Optional) Configures client-to-client route reflection. This feature is enabled by default. This command triggers an automatic soft clear or refresh of BGP neighbor sessions.

Step 6

exit

Example:

switch(config-router-neighbor)# exit

switch(config-router)#

Exits router address configuration mode.

Step 7

neighbor ip-address remote-as as-number

Example:

switch(config-router)# neighbor 192.0.2.10 remote-as 65536

switch(config-router-neighbor)#

Configures the IP address and AS number for a remote BGP peer.

Step 8

address-family {ipv4 | ipv6 | vpnv4 | vpnv6}{unicast | multicast}

Example:

switch(config-router-neighbor)# address-family ipv4 unicast

switch(config-router-neighbor-af)#

Enters neighbor address family configuration mode for the unicast IPv4 address family.

Step 9

route-reflector-client

Example:

switch(config-router-neighbor-af)# route-reflector-client

Configures the device as a BGP route reflector and configures the neighbor as its client. This command triggers an automatic notification and session reset for the BGP neighbor sessions.

Step 10

show bgp {ipv4 | ipv6 | vpnv4 | vpnv6} {unicast | multicast} neighbors

Example:

switch(config-router-neighbor-af)# show bgp ip unicast neighbors

(Optional) Displays the BGP peers.

Step 11

copy running-config startup-config

Example:

switch(config-router-neighbor-af)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to configure the router as a route reflector and add one neighbor as a client:

switch(config)# router bgp 65536

switch(config-router)# neighbor 192.0.2.10 remote-as 65536

switch(config-router-neighbor)# address-family ip unicast

switch(config-router-neighbor-af)# route-reflector-client

switch(config-router-neighbor-af)# copy running-config startup-config

Configuring Route Dampening

You can configure route dampening to minimize route flaps propagating through your iBGP network.

To configure route dampening, use the following command in address-family or VRF address family configuration mode:

Command

Purpose

dampening [{half-life reuse-limit suppress-limit max-suppress-time | route-map map-name}]

Example:

switch(config-router-af)# dampening route-map bgpDamp

Disables capabilities negotiation. The parameter values are as follows:

- half-life—The range is from 1 to 45.

- reuse-limit—The range is from 1 to 20000.

- suppress-limit—The range is from 1 to 20000.

- max-suppress-time—The range is from 1 to 255.

Configuring Load Sharing and ECMP

You can configure the maximum number of paths that BGP adds to the route table for equal-cost multipath load balancing.

Command

Purpose

maximum-paths [ibgp] maxpaths

Configures the maximum number of equal-cost paths for load sharing. The range is from 1 to 16. The default is 1.

Configuring Maximum Prefixes

You can configure the maximum number of prefixes that BGP can receive from a BGP peer. If the number of prefixes exceeds this value, you can optionally configure BGP to generate a warning message or tear down the BGP session to the peer.

Command

Purpose

maximum-prefix maximum [threshold] [restart time | warning-only]

Example:

switch(config-router-neighbor-af)# maximum-prefix 12

Configures the maximum number of prefixes from a peer. The parameter ranges are as follows:

- maximum —The range is from 1 to 300000.

- Threshold —The range is from 1 to 100 percent. The default is 75 percent.

- time —The range is from 1 to 65535 minutes.

This command triggers an automatic notification and session reset for the BGP neighbor sessions if the prefix limit is exceeded.

Configuring Dynamic Capability

You can configure dynamic capability for a BGP peer.

To configure dynamic capability, use the following command in neighbor configuration mode:

Command

Purpose

dynamic-capability

Example:

switch(config-router-neighbor)# dynamic-capability

Enables dynamic capability. This command triggers an automatic notification and session reset for the BGP neighbor sessions.

Configuring Aggregate Addresses

You can configure aggregate address entries in the BGP route table.

To configure an aggregate address, use the following command in router address-family configuration mode:

Command

Purpose

aggregate-address ip-prefix/length [as-set] [summary-only] [advertise-map map-name] [attribute-map map-name] [suppress-map map-name]

Example:

switch(config-router-af)# aggregate-address 192.0.2.0/8 as-set

Creates an aggregate address. The path advertised for this route is an autonomous system set that consists of all elements contained in all paths that are being summarized:

- The as-set keyword generates autonomous system set path information and community information from contributing paths.

- The summary-only keyword filters all more specific routes from updates.

- The advertise-map keyword and argument specify the route map used to select attribute information from selected routes.

- The attribute-map keyword and argument specify the route map used to select attribute information from the aggregate.

- The suppress-map keyword and argument conditionally filter more specific routes.

Configuring BGP Conditional Advertisement

You can configure BGP conditional advertisement to limit the routes that BGP propagates. You define the following two route maps:

- Advertise map—Specifies the conditions that the route must match before BGP considers the conditional advertisement. This route map can contain any appropriate match statements.

- Exist map or nonexist map—Defines the prefix that must exist in the BGP table before BGP propagates a route that matches the advertise map. The nonexist map defines the prefix that must not exist in the BGP table before BGP propagates a route that matches the advertise map. BGP processes only the permit statements in the prefix list match statements in these route maps.

If the route does not pass the condition, BGP withdraws the route if it exists in the BGP table.

BEFORE YOU BEGIN

You must enable BGP (see the “Enabling BGP” section).

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. router bgp as-number

3. neighbor ipaddress remote-as as-number

4. address-family {ipv4 | ipv6 | vpnv4 | vpnv6} {unicast | multicast}

5. advertise-map adv-map {exist-map exist-rmap | non-exist-map nonexist-rmap}

6. (Optional) show ip bgp neighbor

7. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

router bgp as-number

Example:

switch(config)# router bgp 65536

switch(config-router)#

Enters BGP mode and assigns the autonomous system number to the local BGP speaker.

Step 3

neighbor ip-address remote-as as-number

Example:

switch(config-router)# neighbor 192.168.1.2 remote-as 65537

switch(config-router-neighbor)#

Places the router in neighbor configuration mode for BGP routing and configures the neighbor IP address.

Step 4

address-family {ipv4 | ipv6 | vpnv4 | vpnv6} {unicast | multicast}

Example:

switch(config-router-neighbor)# address-family ipv4 multicast

switch(config-router-neighbor-af)#

Enters address family configuration mode.

Step 5

advertise-map adv-map {exist-map exist-rmap | non-exist-map nonexist-rmap}

Example:

switch(config-router-neighbor-af)# advertise-map advertise exist-map exist

Configures BGP to conditionally advertise routes based on the two configured route maps:

- adv-map—Specifies a route map with match statements that the route must pass before BGP passes the route to the next route map. The adv-map is a case-sensitive, alphanumeric string up to 63 characters.

- exist-rmap—Specifies a route map with match statements for a prefix list. A prefix in the BGP table must match a prefix in the prefix list before BGP advertises the route. The exist-rmap is a case-sensitive, alphanumeric string up to 63 characters.

- nonexist-rmap—Specifies a route map with match statements for a prefix list. A prefix in the BGP table must not match a prefix in the prefix list before BGP advertises the route. The nonexist-rmap is a case-sensitive, alphanumeric string up to 63 characters.

Step 6

show ip bgp neighbor

Example:

switch(config-router-neighbor-af)# show ip bgp neighbor

(Optional) Displays information about BGP and the configured conditional advertisement route maps.

Step 7

copy running-config startup-config

Example:

switch(config-router-neighbor-af)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to configure BGP conditional advertisement:

switch# configure terminal

switch(config)# router bgp 65536

switch(config-router)# neighbor 192.0.2.2 remote-as 65537

switch(config-router-neighbor)# address-family ipv4 unicast

switch(config-router-neighbor-af)# advertise-map advertise exist-map exist

switch(config-router-neighbor-af)# exit

switch(config-router-neighbor)# exit

switch(config-router)# exit

switch(config)# route-map advertise

switch(config-route-map)# match as-path pathList

switch(config-route-map)# exit

switch(config)# route-map exit

switch(config-route-map)# match ip address prefix-list plist

switch(config-route-map)# exit

switch(config)# ip prefix-list plist permit 209.165.201.0/27

Configuring Route Redistribution

You can configure BGP to accept routing information from another routing protocol and redistribute that information through the BGP network. Optionally, you can assign a default metric for redistributed routes.

BEFORE YOU BEGIN

You must enable BGP (see the “Enabling BGP” section).

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. router bgp as-number

3. address-family {ipv4 | ipv6 | vpnv4 | vpnv6} {unicast | multicast}

4. redistribute {direct | {eigrp | isis | ospf | ospfv3 | rip} instance-tag | static} route-map map-name

5. (Optional) default-metric value

6. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

router bgp as-number

Example:

switch(config)# router bgp 65536

switch(config-router)#

Enters BGP mode and assigns the autonomous system number to the local BGP speaker.

Step 3

address-family {ipv4 | ipv6 | vpnv4 | vpnv6} {unicast | multicast}

Example:

switch(config-router)# address-family ipv4 unicast

switch(config-router-af)#

Enters address family configuration mode.

Step 4

redistribute {direct | {eigrp | isis | ospf | ospfv3 | rip} instance-tag | static} route-map map-name

Example:

switch(config-router-af)# redistribute eigrp 201 route-map Eigrpmap

Redistributes routes from other protocols into BGP. See the “Configuring Route Maps” section for more information about route maps.

Step 5

default-metric value

Example:

switch(config-router-af)# default-metric 33

(Optional) Generates a default metric into BGP.

Step 6

copy running-config startup-config

Example:

switch(config-router-af)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to redistribute EIGRP into BGP:

switch# configure terminal

switch(config)# router bgp 65536

switch(config-router)# address-family ipv4 unicast

switch(config-router-af)# redistribute eigrp 201 route-map Eigrpmap

switch(config-router-af)# copy running-config startup-config

Configuring Multiprotocol BGP

You can configure MP-BGP to support multiple address families, including IPv4 and IPv6 unicast and multicast routes.

BEFORE YOU BEGIN

You must enable BGP (see the “Enabling BGP” section).

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. router bgp as-number

3. neighbor ip-address remote-as as-number

4. address-family {ipv4 | ipv6 | vpnv4 | vpnv6} {unicast | multicast}

5. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

router bgp as-number

Example:

switch(config)# router bgp 65536

switch(config-router)#

Enters BGP mode and assigns the autonomous system number to the local BGP speaker.

Step 3

neighbor ip-address remote-as as-number

Example:

switch(config-router)# neighbor 192.168.1.2 remote-as 65537

switch(config-router-neighbor)#

Places the router in neighbor configuration mode for BGP routing and configures the neighbor IP address.

Step 4

address-family {ipv4 | ipv6 | vpnv4 | vpnv6} {unicast | multicast}

Example:

switch(config-router-neighbor)# address-family ipv4 multicast

switch(config-router-neighbor-af)#

Enters address family configuration mode.

Step 5

copy running-config startup-config

Example:

switch(config-router-neighbor-af)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to enable advertising and receiving IPv4 and IPv6 routes for multicast RPF for a neighbor:

switch# configure terminal

switch(config)# interface ethernet 2/1

switch(config-if)# ipv6 address 2001:0DB8::1

switch(config-if)# router bgp 65536

switch(config-router)# neighbor 192.168.1.2 remote-as 35537

switch(config-router-neighbor)# address-family ipv4 multicast

switch(config-router-neighbor-af)# exit

switch(config-router-neighbor)# address-family ipv6 multicast

switch(config-router-neighbor-af)# copy running-config startup-config

Tuning BGP

You can tune BGP characteristics through a series of optional parameters.

To tune BGB, use the following optional commands in router configuration mode:

Command

Purpose

bestpath [always-compare-med | compare-routerid | med {missing-as-worst | non-deterministic}]

Example:

switch(config-router)# bestpath always-compare-med

Modifies the best-path algorithm. The optional parameters are as follows:

- always-compare-med —Compares MED on paths from different autonomous systems.

- compare-routerid —Compares the router IDs for identical eBGP paths.

- med missing-as-worst —Treats a missing MED as the highest MED.

- med non-deterministic —Does not always pick the best MED path from among the paths from the same autonomous system.

enforce-first-as

Example:

switch(config-router)# enforce-first-as

Enforces the neighbor autonomous system to be the first AS number listed in the AS_path attribute for eBGP.

log-neighbor-changes

Example:

switch(config-router)# log-neighbor-changes

Generates a system message when a neighbor changes state.

router-id id

Example:

switch(config-router)# router-id 209.165.20.1

Manually configures the router ID for this BGP speaker.

timers [bestpath-delay delay | bgp keepalive holdtime | prefix-peer-timeout timeout]

Example:

switch(config-router)# timers bgp 90 270

Sets the BGP timer values. The optional parameters are as follows:

- delay —Initial best-path timeout value after a restart. The range is from 0 to 3600 seconds. The default value is 300.

- keepalive—BGP session keepalive time. The range is from 0 to 3600 seconds. The default value is 60.

- holdtime—BGP session hold time.The range is from 0 to 3600 seconds. The default value is 180.

- timeout—Prefix peer timeout value. The range is from 0 to 1200 seconds. The default value is 30.

You must manually reset the BGP sessions after configuring this command.

Command

Purpose

distance ebgp-distance ibgp-distance local-distance

Example:

switch(config-router-af)# distance 20 100 200

Sets the administrative distance for BGP. The range is from 1 to 255. The defaults are as follows:

- ebgp-distance—20.

- ibgp-distance—200.

- local-distance—220. Local-distance is the administrative distance used for aggregate discard routes when they are installed in the RIB.

To tune BGP, use the following optional commands in neighbor configuration mode:

Command

Purpose

description string

Example:

switch(config-router-neighbor)# description main site

Sets a descriptive string for this BGP peer. The string can be up to 80 alphanumeric characters.

low-memory exempt

Example:

switch(config-router-neighbor)# low-memory exempt

Exempts this BGP neighbor from a possible shutdown due to a low memory condition.

transport connection-mode passive

Example:

switch(config-router-neighbor)# transport connection-mode passive

Allows a passive connection setup only. This BGP speaker does not initiate a TCP connection to a BGP peer. You must manually reset the BGP sessions after configuring this command.

remove-private-as

Example:

switch(config-router-neighbor)# remove-private-as

Removes private AS numbers from outbound route updates to an eBGP peer. This command triggers an automatic soft clear or refresh of BGP neighbor sessions.

Note See the “Guidelines and Limitations for Advanced BGP” section for more information on this command.

update-source interface-type number

Example:

switch(config-router-neighbor)# update-source ethernet 2/1

Configures the BGP speaker to use the source IP address of the configured interface for BGP sessions to the peer. This command triggers an automatic notification and session reset for the BGP neighbor sessions. Single-hop iBGP peers support fast external failover when update-source is configured.

To tune BGP, use the following optional commands in neighbor address-family configuration mode:

Command

Purpose

suppress-inactive

Example:

switch(config-router-neighbor-af)# suppress-inactive

Advertises the best (active) routes only to the BGP peer. This command triggers an automatic soft clear or refresh of BGP neighbor sessions.

default-originate [route-map map-name]

Example:

switch(config-router-neighbor-af)# default-originate

Generates a default route to the BGP peer.

filter-list list-name {in | out}

Example:

switch(config-router-neighbor-af)# filter-list BGPFilter in

Applies an AS_path filter list to this BGP peer for inbound or outbound route updates. This command triggers an automatic soft clear or refresh of BGP neighbor sessions.

prefix-list list-name {in | out}

Example:

switch(config-router-neighbor-af)# prefix-list PrefixFilter in

Applies a prefix list to this BGP peer for inbound or outbound route updates. This command triggers an automatic soft clear or refresh of BGP neighbor sessions.

send-community

Example:

switch(config-router-neighbor-af)# send-community

Sends the community attribute to this BGP peer. This command triggers an automatic soft clear or refresh of BGP neighbor sessions.

send-community extended

Example:

switch(config-router-neighbor-af)# send-community extended

Sends the extended community attribute to this BGP peer. This command triggers an automatic soft clear or refresh of BGP neighbor sessions.

Configuring a Graceful Restart

You can configure a graceful restart and enable the graceful restart helper feature for BGP.

BEFORE YOU BEGIN

You must enable BGP (see the “Enabling BGP” section).

Create the VDCs and VRFs.

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. router bgp as-number

3. graceful-restart

4. graceful-restart [restart-time time | stalepath-time time]

5. graceful-restart-helper

6. (Optional) show running-config bgp

7. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

router bgp as-number

Example:

switch(config)# router bgp 65536

switch(config-router)#

Creates a new BGP process with the configured autonomous system number.

Step 3

graceful-restart

Example:

switch(config-router)# graceful-restart

Enables a graceful restart and the graceful restart helper functionality. This command is enabled by default.

This command triggers an automatic notification and session reset for the BGP neighbor sessions.

Step 4

graceful-restart [restart-time time | stalepath-time time]

Example:

switch(config-router)# graceful-restart restart-time 300

Configures the graceful restart timers.

The optional parameters are as follows:

- restart-time—Maximum time for a restart sent to the BGP peer. The range is from 1 to 3600 seconds. The default is 120.

- stalepath-time—Maximum time that BGP keeps the stale routes from the restarting BGP peer. The range is from 1 to 3600 seconds. The default is 300.

This command triggers an automatic notification and session reset for the BGP neighbor sessions.

Step 5

graceful-restart-helper

Example:

switch(config-router)# graceful-restart-helper

Enables the graceful restart helper functionality. Use this command if you have disabled graceful restart but you still want to enable graceful restart helper functionality. This command triggers an automatic notification and session reset for the BGP neighbor sessions.

Step 6

show running-config bgp

Example:

switch(config-router)# show running-config bgp

(Optional) Displays the BGP configuration.

Step 7

copy running-config startup-config

Example:

switch(config-router)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to enable a graceful restart:

switch# configure terminal

switch(config)# router bgp 65536

switch(config-router)# graceful-restart

switch(config-router)# copy running-config startup-config

Configuring Virtualization

You can configure one BGP process in each VDC. You can create multiple VRFs within each VDC and use the same BGP process in each VRF.

BEFORE YOU BEGIN

You must enable BGP (see the “Enabling BGP” section).

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. vrf context vrf-name

3. exit

4. router bgp as-number

5. vrf vrf-name

6. neighbor ip-address remote-as as-number

7. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

vrf context vrf-name

Example:

switch(config)# vrf context RemoteOfficeVRF

switch(config-vrf)#

Creates a new VRF and enters VRF configuration mode.

Step 3

exit

Example:

switch(config-vrf)# exit

switch(config)#

Exits VRF configuration mode.

Step 4

router bgp as-number

Example:

switch(config)# router bgp 65536

switch(config-router)#

Creates a new BGP process with the configured autonomous system number.

Step 5

vrf vrf-name

Example:

switch(config-router)# vrf RemoteOfficeVRF

switch(config-router-vrf)#

Enters the router VRF configuration mode and associates this BGP instance with a VRF.

Step 6

neighbor ip-address remote-as as-number

Example:

switch(config-router-vrf)# neighbor 209.165.201.1 remote-as 65536

switch(config-router--vrf-neighbor)#

Configures the IP address and AS number for a remote BGP peer.

Step 7

copy running-config startup-config

Example:

switch(config-router-vrf-neighbor)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to create a VRF and configure the router ID in the VRF:

switch# configure terminal

switch(config)# vrf context NewVRF

switch(config-vrf)# exit

switch(config)# router bgp 65536

switch(config-router)# vrf NewVRF

switch(config-router-vrf)# neighbor 209.165.201.1 remote-as 65536

switch(config-router-vrf-neighbor)# copy running-config startup-config

Verifying the Advanced BGP Configuration

Command

Purpose

show bgp all [summary] [vrf vrf-name]

Displays the BGP information for all address families.

show bgp convergence [vrf vrf-name]

Displays the BGP information for all address families.

show bgp {ipv4 | ipv6 | vpnv4 | vpnv6} {unicast | multicast} [ip-address | ipv6-prefix] community {regexp expression | [community] [no-advertise] [no-export] [no-export-subconfed]} [vrf vrf-name]

Displays the BGP routes that match a BGP community.

show bgp [vrf vrf-name] {ipv4 | ipv6 | vpnv4 | vpnv6} {unicast | multicast} [ip-address | ipv6-prefix] community-list list-name [vrf vrf-name]

Displays the BGP routes that match a BGP community list.

show bgp {ipv4 | ipv6 | vpnv4 | vpnv6} {unicast | multicast} [ip-address | ipv6-prefix] extcommunity {regexp expression | generic [non-transitive | transitive] aa4:nn [exact-match]} [vrf vrf-name]

Displays the BGP routes that match a BGP extended community.

show bgp {ipv4 | ipv6 | vpnv4 | vpnv6} {unicast | multicast} [ip-address | ipv6-prefix] extcommunity-list list-name [exact-match]} [vrf vrf-name]

Displays the BGP routes that match a BGP extended community list.

show bgp {ipv4 | ipv6 | vpnv4 | vpnv6} {unicast | multicast} [ip-address | ipv6-prefix] {dampening dampened-paths [regexp expression]} [vrf vrf-name]

Displays the information for BGP route dampening. Use the clear bgp dampening command to clear the route flap dampening information.

show bgp {ipv4 | ipv6 | vpnv4 | vpnv6} {unicast | multicast} [ip-address | ipv6-prefix] history-paths [regexp expression] [vrf vrf-name]

Displays the BGP route history paths.

show bgp {ipv4 | ipv6 | vpnv4 | vpnv6} {unicast | multicast} [ip-address | ipv6-prefix] filter-list list-name [vrf vrf-name]

Displays the information for the BGP filter list.

show bgp {ipv4 | ipv6 | vpnv4 | vpnv6} {unicast | multicast} [ip-address | ipv6-prefix] neighbors [ip-address | ipv6-prefix] [vrf vrf-name]

Displays the information for BGP peers. Use the clear bgp neighbors command to clear these neighbors.

Displays the information for the BGP route next hop.

show bgp paths

Displays the BGP path information.

show bgp {ipv4 | ipv6 | vpnv4 | vpnv6} {unicast | multicast} [ip-address | ipv6-prefix] policy name [vrf vrf-name]

Displays the BGP policy information. Use the clear bgp policy command to clear the policy information.

show bgp {ipv4 | ipv6 | vpnv4 | vpnv6} {unicast | multicast} [ip-address | ipv6-prefix] prefix-list list-name [vrf vrf-name]

Displays the BGP routes that match the prefix list.

show bgp {ipv4 | ipv6 | vpnv4 | vpnv6} {unicast | multicast} [ip-address | ipv6-prefix] received-paths [vrf vrf-name]

Displays the BGP paths stored for soft reconfiguration.

show bgp {ipv4 | ipv6 | vpnv4 | vpnv6} {unicast | multicast} [ip-address | ipv6-prefix] regexp expression [vrf vrf-name]

Displays the BGP routes that match the AS_path regular expression.

show bgp {ipv4 | ipv6 | vpnv4 | vpnv6} {unicast | multicast} [ip-address | ipv6-prefix] route-map map-name [vrf vrf-name]

Displays the BGP routes that match the route map.

show bgp peer-policy name [vrf vrf-name]

Displays the information about BGP peer policies.

show bgp peer-session name [vrf vrf-name]

Displays the information about BGP peer sessions.

show bgp peer-template name [vrf vrf-name]

Displays the information about BGP peer templates. Use the clear bgp peer-template command to clear all neighbors in a peer template.

show bgp process

Displays the BGP process information.

show {ipv4 | ipv6 | vpnv4 | vpnv6} bgp options

Displays the BGP status and configuration information. This command has multiple options. See the Cisco Nexus 7000 Series NX-OS Unicast Routing Command Reference, Release 5.x, for more information.

show {ipv4 | ipv6 | vpnv4 | vpnv6} mbgp options

Displays the BGP status and configuration information. This command has multiple options. See the Cisco Nexus 7000 Series NX-OS Unicast Routing Command Reference, Release 5.x, for more information.

show running-configuration bgp

Displays the current running BGP configuration.

Monitoring BGP Statistics

To display BGP statistics, use the following commands:

Command

Purpose

show bgp {ipv4 | ipv6 | vpnv4 | vpnv6} {unicast | multicast} [ip-address | ipv6-prefix] flap-statistics [vrf vrf-name]

Displays the BGP route flap statistics. Use the clear bgp flap-statistics command to clear these statistics.

show bgp sessions [vrf vrf-name]

Displays the BGP sessions for all peers. Use the clear bgp sessions command to clear these statistics.

show bgp sessions [vrf vrf-name]

Displays the BGP sessions for all peers. Use the clear bgp sessions command to clear these statistics.

show bgp statistics

Displays the BGP statistics.

Related Topics

The following topics can give more information on BGP:

- Chapter 10, “Configuring Basic BGP”

- Chapter 16, “Configuring Route Policy Manager”

Additional References

For additional information related to implementing BGP, see the following sections:

- Related Documents

- RFCs

- MIBs

Related Documents

Related Topic

Document Title

BGP CLI commands

Cisco Nexus 7000 Series NX-OS Unicast Routing Command Reference, Release 5.x

VDCs and VRFs

Cisco Nexus 7000 Series NX-OS Virtual Device Context Configuration Guide, Release 5.x

RFCs

RFC

Title

RFC 2918

Route Refresh Capability for BGP-4

MIBs

MIBs

MIBs Link

BGP4-MIB

CISCO-BGP4-MIB

To locate and download MIBs, go to the following URL:

http://www.cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml

Feature History for BGP

Table 11-2 Feature History for BGP

Feature Name

Releases

Feature Information

VPN address families

5.2(1)

Added support for VPN address families.

BFD

5.0(2)

Added support for BFD. See the Cisco Nexus 7000 Series NX-OS Interfaces Configuration Guide, Release 5.x, for more information.

ISSU

4.2(3)

Lowered the BGP minimum hold-time check to eight seconds.

Next-hop addressing

4.2(1)

Added support for the BGP next-hop address tracking and filtering.

4-Byte AS numbers

4.2(1)

Added support for 4-byte AS numbers in plaintext notation.

Conditional advertisement

4.2(1)

Added support for conditionally advertising BGP routes based on the existence of other routes in the BGP table.

Dynamic AS number for prefix peers

4.1(2)

Added support for a range of AS numbers for the BGP prefix peer configuration.

BGP

4.0(1)

Configuring Basic BGP

This chapter describes how to configure Border Gateway Protocol (BGP) on the Cisco NX-OS device.

This chapter includes the following sections:

- Information About Basic BGP

- Licensing Requirements for Basic BGP

- Prerequisites for BGP

- Guidelines and Limitations for BGP

- Default Settings

- CLI Configuration Modes

- Configuring Basic BGP

- Verifying the Basic BGP Configuration

- Monitoring BGP Statistics

- Configuration Examples for Basic BGP

- Related Topics

- Where to Go Next

- Additional References

- Feature History for BGP

Information About Basic BGP

Cisco NX-OS supports BGP version 4, which includes multiprotocol extensions that allow BGP to carry routing information for IP multicast routes and multiple Layer 3 protocol address families. BGP uses TCP as a reliable transport protocol to create TCP sessions with other BGP-enabled devices.

BGP uses a path-vector routing algorithm to exchange routing information between BGP-enabled networking devices or BGP speakers. Based on this information, each BGP speaker determines a path to reach a particular destination while detecting and avoiding paths with routing loops. The routing information includes the actual route prefix for a destination, the path of autonomous systems to the destination, and additional path attributes.

BGP selects a single path, by default, as the best path to a destination host or network. Each path carries well-known mandatory, well-known discretionary, and optional transitive attributes that are used in BGP best-path analysis. You can influence BGP path selection by altering some of these attributes by configuring BGP policies. See the “Route Policies and Resetting BGP Sessions” section for more information.

BGP also supports load balancing or equal-cost multipath (ECMP). See the “Load Sharing and Multipath” section for more information.

For information on configuring BGP in an MPLS network, see the Cisco Nexus 7000 Series NX-OS MPLS Configuration Guide.

This section includes the following topics:

- BGP Autonomous Systems

- Administrative Distance

- BGP Peers

- BGP Router Identifier

- BGP Path Selection

- BGP and the Unicast RIB

- BGP Prefix Independent Convergence Core

- BGP Virtualization

BGP Autonomous Systems

An autonomous system (AS) is a network controlled by a single administration entity. An autonomous system forms a routing domain with one or more interior gateway protocols (IGPs) and a consistent set of routing policies. BGP supports 16-bit and 32-bit autonomous system numbers. For more information, see the “Autonomous Systems” section.

Separate BGP autonomous systems dynamically exchange routing information through external BGP (eBGP) peering sessions. BGP speakers within the same autonomous system can exchange routing information through internal BGP (iBGP) peering sessions.

4-Byte AS Number Support

BGP supports 2-byte or 4-byte AS numbers. Cisco NX-OS displays 4-byte AS numbers in plain-text notation (that is, as 32-bit integers). You can configure 4-byte AS numbers as either plain-text notation (for example, 1 to 4294967295) or AS.dot notation (for example, 1.0). For more information, see the “Autonomous Systems” section.

Administrative Distance

An administrative distance is a rating of the trustworthiness of a routing information source. By default, BGP uses the administrative distances shown in Table 10-1.

Table 10-1 BGP Default Administrative Distances

Distance

Default Value

Function

External

20

Applied to routes learned from eBGP.

Internal

200

Applied to routes learned from iBGP.

Local

200

Applied to routes originated by the router.

Note The administrative distance does not influence the BGP path selection algorithm, but it does influence whether BGP-learned routes are installed in the IP routing table.

For more information, see the “Administrative Distance” section.

BGP Peers

A BGP speaker does not discover another BGP speaker automatically. You must configure the relationships between BGP speakers. A BGP peer is a BGP speaker that has an active TCP connection to another BGP speaker.

BGP Sessions

BGP uses TCP port 179 to create a TCP session with a peer. When a TCP connection is established between peers, each BGP peer initially exchanges all of its routes—the complete BGP routing table—with the other peer. After this initial exchange, the BGP peers send only incremental updates when a topology change occurs in the network or when a routing policy change occurs. In the periods of inactivity between these updates, peers exchange special messages called keepalives. The hold time is the maximum time limit that can elapse between receiving consecutive BGP update or keepalive messages.

Cisco NX-OS supports the following peer configuration options:

- Individual IPv4 or IPv4 address—BGP establishes a session with the BGP speaker that matches the remote address and AS number.

- IPv4 or IPv6 prefix peers for a single AS number—BGP establishes sessions with BGP speakers that match the prefix and the AS number.

- Dynamic AS number prefix peers—BGP establishes sessions with BGP speakers that match the prefix and an AS number from a list of configured AS numbers.

Dynamic AS Numbers for Prefix Peers

Cisco NX-OS accepts a range or list of AS numbers to establish BGP sessions. For example, if you configure BGP to use IPv4 prefix 192.0.2.0/8 and AS numbers 33, 66, and 99, BGP establishes a session with 192.0.2.1 with AS number 66 but rejects a session from 192.0.2.2 with AS number 50.

Cisco NX-OS does not associate prefix peers with dynamic AS numbers as either interior BGP (iBGP) or external BGP (eBGP) sessions until after the session is established. See Chapter 11, “Configuring Advanced BGP” for more information on iBGP and eBGP.

Note The dynamic AS number prefix peer configuration overrides the individual AS number configuration that is inherited from a BGP template. For more information, see Chapter 11, “Configuring Advanced BGP”.

BGP Router Identifier

To establish BGP sessions between peers, BGP must have a router ID, which is sent to BGP peers in the OPEN message when a BGP session is established. The BGP router ID is a 32-bit value that is often represented by an IPv4 address. You can configure the router ID. By default, Cisco NX-OS sets the router ID to the IPv4 address of a loopback interface on the router. If no loopback interface is configured on the router, the software chooses the highest IPv4 address configured to a physical interface on the router to represent the BGP router ID. The BGP router ID must be unique to the BGP peers in a network.

If BGP does not have a router ID, it cannot establish any peering sessions with BGP peers.

BGP Path Selection

Although BGP might receive advertisements for the same route from multiple sources, BGP selects only one path as the best path. BGP puts the selected path in the IP routing table and propagates the path to its peers.

The best-path algorithm runs each time that a path is added or withdrawn for a given network. The best-path algorithm also runs if you change the BGP configuration. BGP selects the best path from the set of valid paths available for a given network.

Cisco NX-OS implements the BGP best-path algorithm in the following steps:

Step 1 Compares two paths to determine which is better (see the “Step 1—Comparing Pairs of Paths” section).

Step 2 Explores all paths and determines in which order to compare the paths to select the overall best path (see the “Step 2—Determining the Order of Comparisons” section).

Step 3 Determines whether the old and new best paths differ enough so that the new best path should be used (see the “Step 3—Determining the Best-Path Change Suppression” section).

Note The order of comparison determined in Part 2 is important. Consider the case where you have three paths, A, B, and C. When Cisco NX-OS compares A and B, it chooses A. When Cisco NX-OS compares B and C, it chooses B. But when Cisco NX-OS compares A and C, it might not choose A because some BGP metrics apply only among paths from the same neighboring autonomous system and not among all paths.

The path selection uses the the BGP AS-path attribute. The AS-path attribute includes the list of autonomous system numbers (AS numbers) traversed in the advertised path. If you subdivide your BGP autonomous system into a collection or confederation of autonomous systems, the AS-path contains confederation segments that list these locally defined autonomous systems.

Step 1—Comparing Pairs of Paths

This first step in the BGP best-path algorithm compares two paths to determine which path is better. The following sequence describes the basic steps that Cisco NX-OS uses to compare two paths to determine the better path:

1. Cisco NX-OS chooses a valid path for comparison. (For example, a path that has an unreachable next hop is not valid.)

2. Cisco NX-OS chooses the path with the highest weight.

3. Cisco NX-OS chooses the path with the highest local preference.

4. If one of the paths is locally originated, Cisco NX-OS chooses that path.

5. Cisco NX-OS chooses the path with the shorter AS-path.

Note When calculating the length of the AS-path, Cisco NX-OS ignores confederation segments and counts AS sets as 1. See the “AS Confederations” section for more information.

6. Cisco NX-OS chooses the path with the lower origin. Interior Gateway Protocol (IGP) is considered lower than EGP.

7. Cisco NX-OS chooses the path with the lower multiexit discriminator (MED).

You can configure a number of options that affect whether or not this step is performed. In general, Cisco NX-OS compares the MED of both paths if the paths were received from peers in the same autonomous system; otherwise, Cisco NX-OS skips the MED comparison.

You can configure Cisco NX-OS to always perform the best-path algorithm MED comparison, regardless of the peer autonomous system in the paths. See the “Tuning the Best-Path Algorithm” section for more information. Otherwise, Cisco NX-OS performs a MED comparison that depends on the AS-path attributes of the two paths being compared:

a. If a path has no AS-path or the AS-path starts with an AS_SET, the path is internal and Cisco NX-OS compares the MED to other internal paths.

b. If the AS-path starts with an AS_SEQUENCE, the peer autonomous system is the first AS number in the sequence and Cisco NX-OS compares the MED to other paths that have the same peer autonomous system.

c. If the AS-path contains only confederation segments or starts with confederation segments followed by an AS_SET, the path is internal and Cisco NX-OS compares the MED to other internal paths.

d. If the AS-path starts with confederation segments that are followed by an AS_SEQUENCE, the peer autonomous system is the first AS number in the AS_SEQUENCE and Cisco NX-OS compares the MED to other paths that have the same peer autonomous system.

Note If Cisco NX-OS receives no MED attribute with the path, Cisco NX-OS considers the MED to be 0 unless you configure the best-path algorithm to set a missing MED to the highest possible value. See the “Tuning the Best-Path Algorithm” section for more information.

e. If the nondeterministic MED comparison feature is enabled, the best-path algorithm uses the Cisco IOS style of MED comparison. See the “Tuning the Best-Path Algorithm” section for more information.

8. If one path is from an internal peer and the other path is from an external peer, Cisco NX-OS chooses the path from the external peer.

9. If the paths have different IGP metrics to their next-hop addresses, Cisco NX-OS chooses the path with the lower IGP metric.

10. Cisco NX-OS uses the path that was selected by the best-path algorithm the last time that it was run.

If all path parameters in Step 1 through Step 9 are the same, you can configure the best-path algorithm to compare the router IDs. See the “Tuning the Best-Path Algorithm” section for more information. If the path includes an originator attribute, Cisco NX-OS uses that attribute as the router ID to compare to; otherwise, Cisco NX-OS uses the router ID of the peer that sent the path. If the paths have different router IDs, Cisco NX-OS chooses the path with the lower router ID.

Note When using the attribute originator as the router ID, it is possible that two paths have the same router ID. It is also possible to have two BGP sessions with the same peer router, so you could receive two paths with the same router ID.

11. Cisco NX-OS selects the path with the shorter cluster length. If a path was not received with a cluster list attribute, the cluster length is 0.

12. Cisco NX-OS chooses the path received from the peer with the lower IP address. Locally generated paths (for example, redistributed paths) have a peer IP address of 0.

Note Paths that are equal after Step 9 can be used for multipath if you configure multipath. See the “Load Sharing and Multipath” section for more information.

Step 2—Determining the Order of Comparisons

The second step of the BGP best-path algorithm implementation is to determine the order in which Cisco NX-OS compares the paths:

1. Cisco NX-OS partitions the paths into groups. Within each group, Cisco NX-OS compares the MED among all paths. Cisco NX-OS uses the same rules as in the “Step 1—Comparing Pairs of Paths” section to determine whether MED can be compared between any two paths. Typically, this comparison results in one group being chosen for each neighbor autonomous system. If you configure the bgp bestpath med always command, Cisco NX-OS chooses just one group that contains all the paths.

2. Cisco NX-OS determines the best path in each group by iterating through all paths in the group and keeping track of the best one so far. Cisco NX-OS compares each path with the temporary best path found so far and if the new path is better, it becomes the new temporary best path and Cisco NX-OS compares it with the next path in the group.

3. Cisco NX-OS forms a set of paths that contain the best path selected from each group in Step 2. Cisco NX-OS selects the overall best path from this set of paths by going through them as in Step 2.

Step 3—Determining the Best-Path Change Suppression

The next part of the implementation is to determine whether Cisco NX-OS uses the new best path or suppresses the new best path. The router can continue to use the existing best path if the new one is identical to the old path (if the router ID is the same). Cisco NX-OS continues to use the existing best path to avoid route changes in the network.

You can turn off the suppression feature by configuring the best-path algorithm to compare the router IDs. See the “Tuning the Best-Path Algorithm” section for more information. If you configure this feature, the new best path is always preferred to the existing one.

You cannot suppress the best-path change if any of the following conditions occur:

- The existing best path is no longer valid.

- Either the existing or new best paths were received from internal (or confederation) peers or were locally generated (for example, by redistribution).

- The paths were received from the same peer (the paths have the same router ID).

- The paths have different weights, local preferences, origins, or IGP metrics to their next-hop addresses.

- The paths have different MEDs.

BGP and the Unicast RIB

BGP communicates with the unicast routing information base (unicast RIB) to store IPv4 routes in the unicast routing table. After selecting the best path, if BGP determines that the best path change needs to be reflected in the routing table, it sends a route update to the unicast RIB.

BGP receives route notifications regarding changes to its routes in the unicast RIB. It also receives route notifications about other protocol routes to support redistribution.

BGP also receives notifications from the unicast RIB regarding next-hop changes. BGP uses these notifications to keep track of the reachability and IGP metric to the next-hop addresses.

Whenever the next-hop reachability or IGP metrics in the unicast RIB change, BGP triggers a best-path recalculation for affected routes.

BGP communicates with the IPv6 unicast RIB to perform these operations for IPv6 routes.

BGP Prefix Independent Convergence Core

Cisco NX-OS Release 5.2 introduces the BGP prefix independent convergence (PIC) core feature, which allows for faster convergence for traffic destined to BGP prefixes that share the same remote next hop in case of a failure in the core of the network. Both MPLS and pure IP traffic can benefit from this feature. It is enabled by default and cannot be disabled. For additional considerations when using BGP PIC core in MPLS networks, see the Cisco Nexus 7000 Series NX-OS MPLS Configuration Guide.

BGP Virtualization

BGP supports virtual routing and forwarding (VRF) instances. VRFs exist within virtual device contexts (VDCs). By default, Cisco NX-OS places you in the default VDC and default VRF unless you specifically configure another VDC and VRF. For more information, see the Cisco Nexus 7000 Series NX-OS Virtual Device Context Configuration Guide, Release 5.x, and Chapter14, “Configuring Layer 3 Virtualization”

Licensing Requirements for Basic BGP

The following table shows the licensing requirements for this feature:

Product

License Requirement

Cisco NX-OS

BGP requires an Enterprise Services license. For a complete explanation of the Cisco NX-OS licensing scheme and how to obtain and apply licenses, see the Cisco NX-OS Licensing Guide.

Prerequisites for BGP

BGP has the following prerequisites:

- You must enable BGP (see the “Enabling BGP” section).

- You should have a valid router ID configured on the system.

- You must have an AS number, either assigned by a Regional Internet Registry (RIR) or locally administered.

- You must configure at least one IGP that is capable of recursive next-hop resolution.

- You must configure an address family under a neighbor for the BGP session establishment.

Guidelines and Limitations for BGP

BGP has the following configuration guidelines and limitations:

- The dynamic AS number prefix peer configuration overrides the individual AS number configuration inherited from a BGP template.

- If you configure a dynamic AS number for prefix peers in an AS confederation, BGP establishes sessions with only the AS numbers in the local confederation.

- BGP sessions created through a dynamic AS number prefix peer ignore any configured eBGP multihop time-to-live (TTL) value or a disabled check for directly connected peers.

- Configure a router ID for BGP to avoid automatic router ID changes and session flaps.

- Use the maximum-prefix configuration option per peer to restrict the number of routes received and system resources used.

- Configure the update source to establish a session with BGP/eBGP multihop sessions.

- Specify a BGP policy if you configure redistribution.

- Define the BGP router ID within a VRF.

- If you decrease the keepalive and hold timer values, you might experience BGP session flaps.

- The BGP minimum route advertisement interval (MRAI) value for all iBGP and eBGP sessions is zero and is not configurable.

- If you configure VDCs, install the Advanced Services license and enter the desired VDC (see the Cisco NX-OS Virtual Device Context Configuration Guide).

- If you configure VRFs, install the Advanced Services license and enter the desired VRF (see Chapter 14, “Configuring Layer 3 Virtualization”).

Default Settings

Table 10-2 lists the default settings for BGP parameters.

Table 10-2 Default BGP Parameters

Parameters

Default

BGP feature

Disabled

Keep alive interval

60 seconds

Hold timer

180 seconds

BGP PIC core

Enabled

Auto-summary

Always disabled

Synchronization

Always disabled

CLI Configuration Modes

The following sections describe how to enter each of the CLI configuration modes for BGP. From a mode, you can enter the ? command to display the commands available in that mode.

Global Configuration Mode

Use global configuration mode to create a BGP process and configure advanced features such as AS confederation and route dampening. For more information, see Chapter11, “Configuring Advanced BGP”

The following example shows how to enter router configuration mode:

switch# configuration

switch(config)# router bgp 64496

switch(config-router)#

BGP supports VRF. You can configure BGP within the appropriate VRF if you are using VRFs in your network. See the “Configuring Virtualization” section for more information.

The following example shows how to enter VRF configuration mode:

switch(config)# router bgp 64497

switch(config-router)# vrf vrf_A

switch(config-router-vrf)#

Address Family Configuration Mode

You can optionally configure the address families that BGP supports. Use the address-family command in router configuration mode to configure features for an address family. Use the address-family command in neighbor configuration mode to configure the specific address family for the neighbor.

You must configure the address families if you are using route redistribution, address aggregation, load balancing, and other advanced features.

The following example shows how to enter address family configuration mode from the router configuration mode:

switch(config)# router bgp 64496

switch(config-router)# address-family ipv6 unicast

switch(config-router-af)#

The following example shows how to enter VRF address family configuration mode if you are using VRFs:

switch(config)# router bgp 64497

switch(config-router)# vrf vrf_A

switch(config-router-vrf)# address-family ipv6 unicast

switch(config-router-vrf-af)#

Neighbor Configuration Mode

Cisco NX-OS provides the neighbor configuration mode to configure BGP peers. You can use neighbor configuration mode to configure all parameters for a peer.

The following example shows how to enter neighbor configuration mode:

switch(config)# router bgp 64496

switch(config-router)# neighbor 192.0.2.1

switch(config-router-neighbor)#

The following example shows how to enter VRF neighbor configuration mode:

switch(config)# router bgp 64497

switch(config-router)# vrf vrf_A

switch(config-router-vrf)# neighbor 192.0.2.1

switch(config-router-vrf-neighbor)#

Neighbor Address Family Configuration Mode

An address family configuration submode inside the neighbor configuration submode is available for entering address family-specific neighbor configuration and enabling the address family for the neighbor. Use this mode for advanced features such as limiting the number of prefixes allowed for this neighbor and removing private AS numbers for eBGP.

The following example shows how to enter neighbor address family configuration mode:

switch(config)# router bgp 64496

switch(config-router# neighbor 192.0.2.1

switch(config-router-neighbor)# address-family ipv4 unicast

switch(config-router-neighbor-af)#

The following example shows how to enter VRF neighbor address family configuration mode:

switch(config)# router bgp 64497

switch(config-router)# vrf vrf_A

switch(config-router-vrf)# neighbor 209.165.201.1

switch(config-router-vrf-neighbor)# address-family ipv4 unicast

switch(config-router-vrf-neighbor-af)#

Configuring Basic BGP

To configure a basic BGP, you must enable BGP and configure a BGP peer. Configuring a basic BGP network consists of a few required tasks and many optional tasks. You must configure a BGP routing process and BGP peers.

This section includes the following topics:

- Enabling BGP

- Creating a BGP Instance

- Restarting a BGP Instance

- Shutting Down BGP

- Configuring BGP Peers

- Configuring Dynamic AS Numbers for Prefix Peers

- Clearing BGP Information

Note If you are familiar with the Cisco IOS CLI, be aware that the Cisco NX-OS commands for this feature might differ from the Cisco IOS commands that you would use.

Enabling BGP

You must enable BGP before you can configure BGP.

BEFORE YOU BEGIN

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. feature bgp

3. (Optional) show feature

4. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

feature bgp

Example:

switch(config)# feature bgp

Enables BGP.

Step 3

show feature

Example:

switch(config)# show feature

(Optional) Displays enabled and disabled features.

Step 4

copy running-config startup-config

Example:

switch(config)# copy running-config startup-config

(Optional) Saves this configuration change.

Use the no feature bgp command to disable BGP and remove all associated configuration.

Command

Purpose

no feature bgp

Example:

switch(config)# no feature bgp

Disables BGP and removes all associated configuration.

Creating a BGP Instance

You can create a BGP instance and assign a router ID to the BGP instance. For more information, see the “BGP Router Identifier” section. Cisco NX-OS supports 2-byte or 4-byte autonomous system (AS) numbers in plain-text notation or as.dot notation. See the “4-Byte AS Number Support” section for more information.

BEFORE YOU BEGIN

You must enable BGP (see the “Enabling BGP” section).

BGP must be able to obtain a router ID (for example, a configured loopback address).

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. router bgp autonomous-system-number

3. (Optional) router-id ip-address

4. (Optional) address-family {ipv4 | ipv6 | vpnv4 | vpnv6} {unicast | multicast}

5. (Optional) network ip-prefix [route-map map-name]

6. (Optional) show bgp all

7. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

router bgp autonomous-system-number

Example:

switch(config)# router bgp 64496

switch(config-router)#

Enables BGP and assigns the AS number to the local BGP speaker. The AS number can be a 16-bit integer or a 32-bit integer in the form of a higher 16-bit decimal number and a lower 16-bit decimal number in xx.xx format.

Step 3

router-id ip-address

Example:

switch(config-router)# router-id 192.0.2.255

(Optional) Configures the BGP router ID. This IP address identifies this BGP speaker.

Step 4

address-family {ipv4 | ipv6 | vpnv4 | vpnv6}{unicast | multicast}

Example:

switch(config-router)# address-family ipv4 unicast

switch(config-router-af)#

(Optional) Enters global address family configuration mode for the IP or VPN address family.

Step 5

network ip-prefix [route-map map-name]

Example:

switch(config-router-af)# network 192.0.2.0

(Optional) Specifies a network as local to this autonomous system and adds it to the BGP routing table.

For exterior protocols, the network command controls which networks are advertised. Interior protocols use the network command to determine where to send updates.

Step 6

show bgp all

Example:

switch(config-router-af)# show bgp all

(Optional) Displays information about all BGP address families.

Step 7

copy running-config startup-config

Example:

switch(config-router-af)# copy running-config startup-config

(Optional) Saves this configuration change.

Use the no router bgp command to remove the BGP process and the associated configuration.

Command

Purpose

no router bgp autonomous-system-number

Example:

switch(config)# no router bgp 201

Deletes the BGP process and the associated configuration.

This example shows how to enable BGP with the IPv4 unicast address family and manually add one network to advertise:

switch# configure terminal

switch(config)# router bgp 64496

switch(config-router)# address-family ipv4 unicast

switch(config-router-af)# network 192.0.2.0

switch(config-router-af)# copy running-config startup-config

Restarting a BGP Instance

You can restart a BGP instance and clear all peer sessions for the instance.

To restart a BGP instance and remove all associated peers, use the following command:

Command

Purpose

restart bgp instance-tag

Example:

switch(config)# restart bgp 201

Restarts the BGP instance and resets or reestablishes all peering sessions.

Shutting Down BGP

You can shut down the BGP and gracefully disable BGP while retaining the configuration.

To shut down BGP, use the following command in router configuration mode:

Command

Purpose

shutdown

Example:

switch(config-router)# shutdown

Gracefully shuts down BGP.

Configuring BGP Peers

You can configure a BGP peer within a BGP process. Each BGP peer has an associated keepalive timer and hold timers. You can set these timers either globally or for each BGP peer. A peer configuration overrides a global configuration.

Note You must configure the address family under neighbor configuration mode for each peer.

BEFORE YOU BEGIN

You must enable BGP (see the “Enabling BGP” section).

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. router bgp autonomous-system-number

3. neighbor {ip-address | ipv6-address} remote-as as-number

4. (Optional) description text

5. (Optional) timers keepalive-time hold-time

6. (Optional) shutdown

7. address-family {ipv4 | ipv6 | vpnv4 | vpnv6}{unicast | multicast}

8. (Optional) show bgp {ipv4 | ipv6 | vpnv4 | vpnv6} {unicast | multicast} neighbors

9. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

router bgp autonomous-system-number

Example:

switch(config)# router bgp 64496

switch(config-router)#

Enables BGP and assigns the AS number to the local BGP speaker. The AS number can be a 16-bit integer or a 32-bit integer in the form of a higher 16-bit decimal number and a lower 16-bit decimal number in xx.xx format.

Step 3

neighbor {ip-address | ipv6-address} remote-as as-number

Example:

switch(config-router)# neighbor 209.165.201.1 remote-as 64497

switch(config-router-neighbor)#

Configures the IPv4 or IPv6 address and AS number for a remote BGP peer. The ip-address format is x.x.x.x. The ipv6-address format is A:B::C:D.

Step 4

description text

Example:

switch(config-router-neighbor)# description Peer Router B

switch(config-router-neighbor)#

(Optional) Adds a description for the neighbor. The description is an alphanumeric string up to 80 characters.

Step 5

timers keepalive-time hold-time

Example:

switch(config-router-neighbor)# timers 30 90

(Optional) Adds the keepalive and hold time BGP timer values for the neighbor. The range is from 0 to 3600 seconds. The default is 60 seconds for the keepalive time and 180 seconds for the hold time.

Step 6

shutdown

Example:

switch(config-router-neighbor)# shutdown

(Optional). Administratively shuts down this BGP neighbor. This command triggers an automatic notification and session reset for the BGP neighbor sessions.

Step 7

address-family {ipv4 | ipv6 | vpnv4 | vpnv6}{unicast | multicast}

Example:

switch(config-router-neighbor)# address-family ipv4 unicast

switch(config-router-neighbor-af)#

Enters neighbor address family configuration mode for the unicast IPv4 address family.

Step 8

show bgp {ipv4 | ipv6 | vpnv4 | vpnv6}{unicast | multicast} neighbors

Example:

switch(config-router-neighbor-af)# show bgp ipv4 unicast neighbors

(Optional) Displays information about BGP peers.

Step 9

copy running-config startup-config

Example:

switch(config-router-neighbor-af) copy running-config startup-config

(Optional) Saves this configuration change.

The following example shows how to configure a BGP peer:

switch# configure terminal

switch(config)# router bgp 64496

switch(config-router)# neighbor 192.0.2.1 remote-as 64497

switch(config-router-neighbor)# description Peer Router B

switch(config-router-neighbor)# address-family ipv4 unicast

switch(config-router-neighbor-af)# copy running-config startup-config

Configuring Dynamic AS Numbers for Prefix Peers

You can configure multiple BGP peers within a BGP process. You can limit BGP session establishment to a single AS number or multiple AS numbers in a route map.

BGP sessions configured through dynamic AS numbers for prefix peers ignore the ebgp-multihop command and the disable-connected-check command.

You can change the list of AS numbers in the route map, but you must use the no neighbor command to change the route-map name. Changes to the AS numbers in the configured route map affect only new sessions.

BEFORE YOU BEGIN

You must enable BGP (see the “Enabling BGP” section).

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. router bgp autonomous-system-number

3. neighbor prefix remote-as route-map map-name

4. (Optional) show bgp {ipv4 | ipv6 | vpnv4 | vpnv6} {unicast | multicast} neighbors

5. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

router bgp autonomous-system-number

Example:

switch(config)# router bgp 64496

switch(config-router)#

Enables BGP and assigns the AS number to the local BGP speaker. The AS number can be a 16-bit integer or a 32-bit integer in the form of a higher 16-bit decimal number and a lower 16-bit decimal number in xx.xx format.

Step 3

neighbor prefix remote-as route-map map-name

Example:

switch(config-router)# neighbor 192.0.2.0/8 remote-as routemap BGPPeers

switch(config-router-neighbor)#

Configures the IPv4 or IPv6 prefix and a route map for the list of accepted AS numbers for the remote BGP peers. The prefix format for IPv4 is x.x.x.x/length. The length range is from 1 to 32. The prefix format for IPv6 is A:B::C:D/length. The length range is from 1 to 128.

The map-name can be any case-sensitive, alphanumeric string up to 63 characters.

Step 4

show bgp {ipv4 | ipv6 | vpnv4 | vpnv6}{unicast | multicast} neighbors

Example:

switch(config-router-neighbor-af)# show bgp ipv4 unicast neighbors

(Optional) Displays information about BGP peers.

Step 5

copy running-config startup-config

Example:

switch(config-router-neighbor-af)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to configure dynamic AS numbers for a prefix peer:

switch# configure terminal

switch(config)# route-map BGPPeers

switch(config-route-map)# match as-number 64496, 64501-64510

switch(config-route-map)# match as-number as-path-list List1, List2

switch(config-route-map)# exit

switch(config)# router bgp 64496

switch(config-router)# neighbor 192.0.2.0/8 remote-as route-map BGPPeers

switch(config-router-neighbor)# description Peer Router B

switch(config-router-neighbor)# address-family ipv4 unicast

switch(config-router-neighbor-af)# copy running-config startup-config

See Chapter16, “Configuring Route Policy Manager” for information on route maps.

Clearing BGP Information

To clear BGP information, use the following commands:

Command

Purpose

clear bgp all {neighbor | * | as-number | peer-template name | prefix} [vrf vrf-name]

Clears one or more neighbors from all address families. * clears all neighbors in all address families. The arguments are as follows:

- neighbor —IPv4 or IPv6 address of a neighbor.

- as-number — Autonomous system number. The AS number can be a 16-bit integer or a 32-bit integer in the form of higher 16-bit decimal number and a lower 16-bit decimal number in xx.xx format.

- name —Peer template name. The name can be any case-sensitive, alphanumeric string up to 64 characters.

- prefix —IPv4 or IPv6 prefix. All neighbors within that prefix are cleared.

- vrf-name —VRF name. All neighbors in that VRF are cleared. The name can be any case-sensitive, alphanumeric string up to 64 characters.

clear bgp all dampening [vrf vrf-name]

Clears route flap dampening networks in all address families. The vrf-name can be any case-sensitive, alphanumeric string up to 64 characters.

clear bgp all flap-statistics [vrf vrf-name]

Clears route flap statistics in all address families. The vrf-name can be any case-sensitive, alphanumeric string up to 64 characters.

clear bgp {ipv4 | ipv6 | vpnv4 | vpnv6} {unicast | multicast} dampening [vrf vrf-name]

Clears route flap dampening networks in the selected address family. The vrf-name can be any case-sensitive, alphanumeric string up to 64 characters.

clear bgp {ipv4 | ipv6 | vpnv4 | vpnv6} {unicast | multicast} flap-statistics [vrf vrf-name]

Clears route flap statistics in the selected address family. The vrf-name can be any case-sensitive, alphanumeric string up to 64 characters.

clear bgp {ipv4 | ipv6 | vpnv4 | vpnv6} {unicast | multicast} {neighbor | * | as-number | peer-template name | prefix} [vrf vrf-name]

Clears one or more neighbors from the selected address family. * clears all neighbors in the address family. The arguments are as follows:

- neighbor —IPv4 or IPv6 address of a neighbor.

- as-number — Autonomous system number. The AS number can be a 16-bit integer or a 32-bit integer in the form of higher 16-bit decimal number and a lower 16-bit decimal number in xx.xx format.

- name —Peer template name. The name can be any case-sensitive, alphanumeric string up to 64 characters.

- prefix —IPv4 or IPv6 prefix. All neighbors within that prefix are cleared.

- vrf-name —VRF name. All neighbors in that VRF are cleared. The name can be any case-sensitive, alphanumeric string up to 64 characters.

clear ip bgp {ip {unicast | multicast}} {neighbor | * | as-number | peer-template name | prefix} [vrf vrf-name]

Clears one or more neighbors. * clears all neighbors in the address family. The arguments are as follows:

- neighbor —IPv4 or IPv6 address of a neighbor.

- as-number — Autonomous system number. The AS number can be a 16-bit integer or a 32-bit integer in the form of higher 16-bit decimal number and a lower 16-bit decimal number in xx.xx format.

- name —Peer template name. The name can be any case-sensitive, alphanumeric string up to 64 characters.

- prefix —IPv4 or IPv6 prefix. All neighbors within that prefix are cleared.

- vrf-name —VRF name. All neighbors in that VRF are cleared. The name can be any case-sensitive, alphanumeric string up to 64 characters.

clear ip bgp dampening [ip-neighbor | ip-prefix] [vrf vrf-name]

Clears route flap dampening in one or more networks. The arguments are as follows:

- ip-neighbor —IPv4 address of a neighbor.

- ip-prefix —IPv4. All neighbors within that prefix are cleared.

- vrf-name —VRF name. All neighbors in that VRF are cleared. The name can be any case-sensitive, alphanumeric string up to 64 characters.

clear ip bgp flap-statistics [ip-neighbor | ip-prefix] [vrf vrf-name]

Clears route flap statistics in one or more networks. The arguments are as follows:

- ip-neighbor —IPv4 address of a neighbor.

- ip-prefix —IPv4. All neighbors within that prefix are cleared.

- vrf-name —VRF name. All neighbors in that VRF are cleared. The name can be any case-sensitive, alphanumeric string up to 64 characters.

clear ip mbgp {ip {unicast | multicast}} {neighbor | * | as-number | peer-template name | prefix} [vrf vrf-name]

Clears one or more neighbors. * clears all neighbors in the address family. The arguments are as follows:

- neighbor —IPv4 or IPv6 address of a neighbor.

- as-number — Autonomous system number. The AS number can be a 16-bit integer or a 32-bit integer in the form of higher 16-bit decimal number and a lower 16-bit decimal number in xx.xx format.

- name —Peer template name. The name can be any case-sensitive, alphanumeric string up to 64 characters.

- prefix —IPv4 or IPv6 prefix. All neighbors within that prefix are cleared.

- vrf-name —VRF name. All neighbors in that VRF are cleared. The name can be any case-sensitive, alphanumeric string up to 64 characters.

clear ip mbgp dampening [ip-neighbor | ip-prefix] [vrf vrf-name]

Clears route flap dampening in one or more networks. The arguments are as follows:

- ip-neighbor —IPv4 address of a neighbor.

- ip-prefix —IPv4. All neighbors within that prefix are cleared.

- vrf-name —VRF name. All neighbors in that VRF are cleared. The name can be any case-sensitive, alphanumeric string up to 64 characters.

clear ip mbgp flap-statistics [ip-neighbor | ip-prefix] [vrf vrf-name]

Clears route flap statistics one or more networks. The arguments are as follows:

- ip-neighbor —IPv4 address of a neighbor.

- ip-prefix —IPv4. All neighbors within that prefix are cleared.

- vrf-name —VRF name. All neighbors in that VRF are cleared. The name can be any case-sensitive, alphanumeric string up to 64 characters.

Verifying the Basic BGP Configuration

To display the BGP configuration, perform one of the following tasks:

Command

Purpose

show bgp all [summary] [vrf vrf-name]

Displays the BGP information for all address families.

show bgp convergence [vrf vrf-name]

Displays the BGP information for all address families.

show bgp {ipv4 | ipv6 | vpnv4 | vpnv6} {unicast | multicast} [ip-address | ipv6-prefix] community {regexp expression | [community] [no-advertise] [no-export] [no-export-subconfed]} [vrf vrf-name]

Displays the BGP routes that match a BGP community.

show bgp [vrf vrf-name] {ipv4 | ipv6 | vpnv4 | vpnv6} {unicast | multicast} [ip-address | ipv6-prefix] community-list list-name [vrf vrf-name]

Displays the BGP routes that match a BGP community list.

show bgp {ipv4 | ipv6 | vpnv4 | vpnv6} {unicast | multicast} [ip-address | ipv6-prefix] extcommunity {regexp expression | generic [non-transitive | transitive] aa4:nn [exact-match]} [vrf vrf-name]

Displays the BGP routes that match a BGP extended community.

show bgp {ipv4 | ipv6 | vpnv4 | vpnv6} {unicast | multicast} [ip-address | ipv6-prefix] extcommunity-list list-name [exact-match]} [vrf vrf-name]

Displays the BGP routes that match a BGP extended community list.

show bgp {ipv4 | ipv6 | vpnv4 | vpnv6} {unicast | multicast} [ip-address | ipv6-prefix] {dampening dampened-paths [regexp expression]} [vrf vrf-name]

Displays the information for BGP route dampening. Use the clear bgp dampening command to clear the route flap dampening information.

show bgp {ipv4 | ipv6 | vpnv4 | vpnv6} {unicast | multicast} [ip-address | ipv6-prefix] history-paths [regexp expression] [vrf vrf-name]

Displays the BGP route history paths.

show bgp {ipv4 | ipv6 | vpnv4 | vpnv6} {unicast | multicast} [ip-address | ipv6-prefix] filter-list list-name [vrf vrf-name]

Displays the information for the BGP filter list.

show bgp {ipv4 | ipv6 | vpnv4 | vpnv6} {unicast | multicast} [ip-address | ipv6-prefix] neighbors [ip-address | ipv6-prefix] [vrf vrf-name]

Displays the information for BGP peers. Use the clear bgp neighbors command to clear these neighbors.

show bgp {ipv4 | ipv6 | vpnv4 | vpnv6} {unicast | multicast} [ip-address | ipv6-prefix] {nexthop | nexthop-database} [vrf vrf-name]

Displays the information for the BGP route next hop.

show bgp paths

Displays the BGP path information.

show bgp {ipv4 | ipv6 | vpnv4 | vpnv6} {unicast | multicast} [ip-address | ipv6-prefix] policy name [vrf vrf-name]

Displays the BGP policy information. Use the clear bgp policy command to clear the policy information.

show bgp {ipv4 | ipv6 | vpnv4 | vpnv6} {unicast | multicast} [ip-address | ipv6-prefix] prefix-list list-name [vrf vrf-name]

Displays the BGP routes that match the prefix list.

show bgp {ipv4 | ipv6 | vpnv4 | vpnv6} {unicast | multicast} [ip-address | ipv6-prefix] received-paths [vrf vrf-name]

Displays the BGP paths stored for soft reconfiguration.

show bgp {ipv4 | ipv6 | vpnv4 | vpnv6} {unicast | multicast} [ip-address | ipv6-prefix] regexp expression [vrf vrf-name]

Displays the BGP routes that match the AS_path regular expression.

show bgp {ipv4 | ipv6 | vpnv4 | vpnv6} {unicast | multicast} [ip-address | ipv6-prefix] route-map map-name [vrf vrf-name]

Displays the BGP routes that match the route map.

show bgp peer-policy name [vrf vrf-name]

Displays the information about BGP peer policies.

show bgp peer-session name [vrf vrf-name]

Displays the information about BGP peer sessions.

show bgp peer-template name [vrf vrf-name]

Displays the information about BGP peer templates. Use the clear bgp peer-template command to clear all neighbors in a peer template.

show bgp process

Displays the BGP process information.

show {ip | ipv6} bgp options

Displays the BGP status and configuration information. This command has multiple options. See the Cisco Nexus 7000 Series NX-OS Unicast Routing Command Reference, Release 5.x, for more information.

show {ip | ipv6} mbgp options

Displays the BGP status and configuration information. This command has multiple options. See the Cisco Nexus 7000 Series NX-OS Unicast Routing Command Reference, Release 5.x, for more information.

show running-configuration bgp

Displays the current running BGP configuration.

Monitoring BGP Statistics

To display BGP statistics, use the following commands:

Command

Purpose

show bgp {ipv4 | ipv6 | vpnv4 | vpnv6} {unicast | multicast} [ip-address | ipv6-prefix] flap-statistics [vrf vrf-name]

Displays the BGP route flap statistics. Use the clear bgp flap-statistics command to clear these statistics.

show bgp sessions [vrf vrf-name]

Displays the BGP sessions for all peers. Use the clear bgp sessions command to clear these statistics.

show bgp sessions [vrf vrf-name]

Displays the BGP sessions for all peers. Use the clear bgp sessions command to clear these statistics.

show bgp statistics

Displays the BGP statistics.

Configuration Examples for Basic BGP

This example shows a basic BGP configuration:

feature bgp

router bgp 64496

neighbor 2001:ODB8:0:1::55 remote-as 64496

address-family ipv6 unicast

next-hop-self

Related Topics

The following topics relate to BGP:

- Chapter16, “Configuring Route Policy Manager”

Where to Go Next

See Chapter 11, “Configuring Advanced BGP” for details on the following features:

- Peer templates

- Route redistribution

- Route maps

Additional References

For additional information related to implementing BGP, see the following sections:

- Related Documents

- RFCs

- MIBs

Related Documents

Related Topic

Document Title

BGP CLI commands

Cisco Nexus 7000 Series NX-OS Unicast Routing Command Reference, Release 5.x

MPLS configuration

Cisco Nexus 7000 Series NX-OS MPLS Configuration Guide

VDCs and VRFs

Cisco Nexus 7000 Series NX-OS Virtual Device Context Configuration Guide, Release 5.x

RFCs

RFC

Title

RFC 2918

Route Refresh Capability for BGP-4

MIBs

MIBs

MIBs Link

BGP4-MIB

CISCO-BGP4-MIB

To locate and download MIBs, go to the following URL:

http://www.cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml

Feature History for BGP

Table 10-3 lists the release history for this feature.

Table 10-3 Feature History for BGP

Feature Name

Releases

Feature Information

BGP

5.2(1)

Added support for the BGP PIC core feature.

VPN address families

5.2(1)

Added support for VPN address families.

BFD

5.0(2)

Added support for BFD. See the Cisco Nexus 7000 Series NX-OS Interfaces Configuration Guide, Release 5.x for more information.

ISSU

4.2(3)

Lowered BGP minimum hold-time check to eight seconds.

IPv6

4.2(1)

Added support for IPv6.

4-Byte AS numbers

4.2(1)

Added support for 4-byte AS numbers in plaintext notation.

Conditional advertisement

4.2(1)

Added support for conditionally advertising BGP routes based on the existence of other routes in the BGP table.

Dynamic AS number for prefix peers

4.1(2)

Added support for a range of AS numbers for BGP prefix peer configuration.

BGP

4.0(1)

This feature was introduced.

Configuring EIGRP

This chapter describes how to configure the Enhanced Interior Gateway Routing Protocol (EIGRP) on the Cisco NX-OS device.

This chapter includes the following sections:

- Information About EIGRP

- Licensing Requirements for EIGRP

- Prerequisites for EIGRP

- Guidelines and Limitations for EIGRP

- Default Settings

- Configuring Basic EIGRP

- Configuring Advanced EIGRP

- Configuring Virtualization for EIGRP

- Verifying the EIGRP Configuration

- Monitoring EIGRP

- Configuration Examples for EIGRP

- Related Topics

- Additional References

- Feature History for EIGRP

Information About EIGRP

EIGRP combines the benefits of distance vector protocols with the features of link-state protocols. EIGRP sends out periodic Hello messages for neighbor discovery. Once EIGRP learns a new neighbor, it sends a one-time update of all the local EIGRP routes and route metrics. The receiving EIGRP router calculates the route distance based on the received metrics and the locally assigned cost of the link to that neighbor. After this initial full route table update, EIGRP sends incremental updates to only those neighbors affected by the route change. This process speeds convergence and minimizes the bandwidth used by EIGRP.

This section includes the following topics:

- EIGRP Components

- EIGRP Route Updates

- Advanced EIGRP

EIGRP Components

EIGRP has the following basic components:

- Reliable Transport Protocol

- Neighbor Discovery and Recovery

- Diffusing Update Algorithm

Reliable Transport Protocol

The Reliable Transport Protocol guarantees ordered delivery of EIGRP packets to all neighbors. (See the “Neighbor Discovery and Recovery” section.) The Reliable Transport Protocol supports an intermixed transmission of multicast and unicast packets. The reliable transport can send multicast packets quickly when unacknowledged packets are pending. This provision helps to ensure that the convergence time remains low for various speed links. See the “Configuring Advanced EIGRP” section for details about modifying the default timers that control the multicast and unicast packet transmissions.

The Reliable Transport Protocol includes the following message types:

- Hello—Used for neighbor discovery and recovery. By default, EIGRP sends a periodic multicast Hello message on the local network at the configured hello interval . By default, the hello interval is 5 seconds.

- Acknowledgement—Verify reliable reception of Updates, Queries, and Replies.

- Updates—Send to affected neighbors when routing information changes. Updates include the route destination, address mask, and route metrics such as delay and bandwidth. The update information is stored in the EIGRP topology table.

- Queries and Replies—Sent as part of the Diffusing Update Algorithm used by EIGRP.

Neighbor Discovery and Recovery

EIGRP uses the Hello messages from the Reliable Transport Protocol to discover neighboring EIGRP routers on directly attached networks. EIGRP adds neighbors to the neighbor table. The information in the neighbor table includes the neighbor address, the interface it was learned on, and the hold time, which indicates how long EIGRP should wait before declaring a neighbor unreachable. By default, the hold time is three times the hello interval or 15 seconds.

EIGRP sends a series of Update messages to new neighbors to share the local EIGRP routing information. This route information is stored in the EIGRP topology table. After this initial transmission of the full EIGRP route information, EIGRP sends Update messages only when a routing change occurs. These Update messages contain only the new or changed information and are sent only to the neighbors affected by the change. See the “EIGRP Route Updates” section.

EIGRP also uses the Hello messages as a keepalive to its neighbors. As long as Hello messages are received, Cisco NX-OS can determine that a neighbor is alive and functioning.

Diffusing Update Algorithm

The Diffusing Update Algorithm (DUAL) calculates the routing information based on the destination networks in the topology table. The topology table includes the following information:

- IPv4 or IPv6 address/mask—The network address and network mask for this destination.

- Successors—The IP address and local interface connection for all feasible successor s or neighbors that advertise a shorter distance to the destination than the current feasible distance .

- Feasibility distance (FD)—The lowest calculated distance to the destination. The feasibility distance is the sum of the advertised distance from a neighbor plus the cost of the link to that neighbor.

DUAL uses the distance metric to select efficient, loop-free paths. DUAL selects routes to insert into the unicast Routing Information Base (RIB) based on feasible successors. When a topology change occurs, DUAL looks for feasible successors in the topology table. If there are feasible successors, DUAL selects the feasible successor with the lowest feasible distance and inserts that into the unicast RIB, avoiding unnecessary recomputation.

When there are no feasible successors but there are neighbors advertising the destination, DUAL transitions from the passive state to the active state and triggers a recomputation to determine a new successor or next-hop router to the destination. The amount of time required to recompute the route affects the convergence time. EIGRP sends Query messages to all neighbors, searching for feasible successors. Neighbors that have a feasible successor send a Reply message with that information. Neighbors that do not have feasible successors trigger a DUAL recomputation.

EIGRP Route Updates

When a topology change occurs, EIGRP sends an Update message with only the changed routing information to affected neighbors. This Update message includes the distance information to the new or updated network destination.

The distance information in EIGRP is represented as a composite of available route metrics, including bandwidth, delay, load utilization, and link reliability. Each metric has an associated weight that determines if the metric is included in the distance calculation. You can configure these metric weights. You can fine-tune link characteristics to achieve optimal paths, but we recommend that you use the default settings for most configurable metrics.

This section includes the following topics:

- Internal Route Metrics

- Wide Metrics

- External Route Metrics

- EIGRP and the Unicast RIB

Internal Route Metrics

Internal routes are routes that occur between neighbors within the same EIGRP autonomous system. These routes have the following metrics:

- Next hop—The IP address of the next-hop router.

- Delay—The sum of the delays configured on the interfaces that make up the route to the destination network. The delay is configured in tens of microseconds.

- Bandwidth—The calculation from the lowest configured bandwidth on an interface that is part of the route to the destination.

Note We recommend that you use the default bandwidth value. This bandwidth parameter is also used by EIGRP.

- MTU—The smallest maximum transmission unit value along the route to the destination.

- Hop count—The number of hops or routers that the route passes through to the destination. This metric is not directly used in the DUAL computation.

- Reliability—An indication of the reliability of the links to the destination.

- Load—An indication of how much traffic is on the links to the destination.

By default, EIGRP uses the bandwidth and delay metrics to calculate the distance to the destination. You can modify the metric weights to include the other metrics in the calculation.

Wide Metrics

EIGRP supports wide (64-bit) metrics to improve route selection on higher-speed interfaces or bundled interfaces. Routers supporting wide metrics can interoperate with routers that do not support wide metrics as follows:

- A router that supports wide metrics—Adds local wide metrics values to the received values and sends the information on.

- A router that does not support wide metrics— Sends any received metrics on without changing the values.

EIGRP uses the following equation to calculate path cost with wide metrics:

metric = [k1 x bandwidth + (k2 x bandwidth)/(256 – load) + k3 x delay + k6 xextended attributes] x [k5/(reliability + k4)]

Since the unicast RIB cannot support 64-bit metric values, EIGRP wide metrics use the following equation with a RIB scaling factor to convert the 64-bit metric value to a 32-bit value:

RIB Metric = (Wide Metric / RIB scale value).

where the RIB scale value is a configurable parameter.

EIGRP wide metrics introduce the following two new metric values represented as k6 in the EIGRP metrics configuration:

- Jitter—(Measured in microseconds) accumulated across all links in the route path. Routes lower jitter values are preferred for EIGRP path selection.

- Energy—(Measured in watts per kilobit) accumulated across all links in the route path. Routes lower energy values are preferred for EIGRP path selection.

EIGRP prefers a path with no jitter or energy metric values or lower jitter or metric values over a path with higher values.

Note EIGRP wide metrics are sent with a TLV version of 2. For more information, see the “Enabling Wide Metrics” section.

External Route Metrics

External routes are routes that occur between neighbors in different EIGRP autonomous systems. These routes have the following metrics:

- Next hop—The IP address of the next-hop router.

- Router ID—The router ID of the router that redistributed this route into EIGRP.

- AS number—The autonomous system number of the destination.

- Protocol ID—A code that represents the routing protocol that learned the destination route.

- Tag—An arbitrary tag that can be used for route maps.

- Metric—The route metric for this route from the external routing protocol.

EIGRP and the Unicast RIB

EIGRP adds all learned routes to the EIGRP topology table and the unicast RIB. When a topology change occurs, EIGRP uses these routes to search for a feasible successor. EIGRP also listens for notifications from the unicast RIB for changes in any routes redistributed to EIGRP from another routing protocol.

Advanced EIGRP

You can use the advanced features of EIGRP to optimize your EIGRP configuration.

This section includes the following topics:

- Address Families

- Authentication

- Stub Routers

- Route Summarization

- Route Redistribution

- Load Balancing

- Split Horizon

- BFD

- Virtualization Support

- Graceful Restart and High Availability

Address Families

EIGRP supports both IPv4 and IPv6 address families. For backward compatibility, you can configure EIGRPv4 in route configuration mode or in IPV4 address family mode. You must configure EIGRP for IPv6 in address family mode.

Address family configuration mode includes the following EIGRP features:

- Authentication

- AS number

- Default route

- Metrics

- Distance

- Graceful restart

- Logging

- Load balancing

- Redistribution

- Router ID

- Stub router

- Timers

You cannot configure the same feature in more than one configuration mode. For example, if you configure the default metric in router configuration mode, you cannot configure the default metric in address family mode.

Authentication

You can configure authentication on EIGRP messages to prevent unauthorized or invalid routing updates in your network. EIGRP authentication supports MD5 authentication digest.

You can configure the EIGRP authentication per virtual routing and forwarding (VRF) instance or interface using key-chain management for the authentication keys. Key-chain management allows you to control changes to the authentication keys used by MD5 authentication digest. See the Cisco Nexus 7000 Series NX-OS Security Configuration Guide, Release 5.x, for more details about creating key chains.

For MD5 authentication, you configure a password that is shared at the local router and all remote EIGRP neighbors. When an EIGRP message is created, Cisco NX-OS creates an MD5 one-way message digest based on the message itself and the encrypted password and sends this digest along with the EIGRP message. The receiving EIGRP neighbor validates the digest using the same encrypted password. If the message has not changed, the calculation is identical and the EIGRP message is considered valid.

MD5 authentication also includes a sequence number with each EIGRP message that is used to ensure that no message is replayed in the network.

Stub Routers

You can use the EIGRP stub routing feature to improve network stability, reduce resource usage, and simplify stub router configuration. Stub routers connect to the EIGRP network through a remote router. See the “Stub Routing” section.

When using EIGRP stub routing, you need to configure the distribution and remote routers to use EIGRP and configure only the remote router as a stub. EIGRP stub routing does not automatically enable summarization on the distribution router. In most cases, you need to configure summarization on the distribution routers.

Without EIGRP stub routing, even after the routes that are sent from the distribution router to the remote router have been filtered or summarized, a problem might occur. For example, if a route is lost somewhere in the corporate network, EIGRP could send a query to the distribution router. The distribution router could then send a query to the remote router even if routes are summarized. If a problem communicating over the WAN link between the distribution router and the remote router occurs, EIGRP could get stuck in an active condition and cause instability elsewhere in the network. EIGRP stub routing allows you to prevent queries to the remote router.

Route Summarization

You can configure a summary aggregate address for a specified interface. Route summarization simplifies route tables by replacing a number of more-specific addresses with an address that represents all the specific addresses. For example, you can replace 10.1.1.0/24, 10.1.2.0/24, and 10.1.3.0/24 with one summary address, 10.1.0.0/16.

If more specific routes are in the routing table, EIGRP advertises the summary address from the interface with a metric equal to the minimum metric of the more specific routes.

Note EIGRP does not support automatic route summarization.

Route Redistribution

You can use EIGRP to redistribute static routes, routes learned by other EIGRP autonomous systems, or routes from other protocols. You must configure a route map with the redistribution to control which routes are passed into EIGRP. A route map allows you to filter routes based on attributes such as the destination, origination protocol, route type, route tag, and so on. See Chapter16, “Configuring Route Policy Manager”

You also configure the default metric that is used for all imported routes into EIGRP.

You use distribute lists to filter routes from routing updates. These filtered routes are applied to each interface with the ip distribute-list eigrp command.

Load Balancing

You can use load balancing to allow a router to distribute traffic over all the router network ports that are the same distance from the destination address. Load balancing increases the usage of network segments, which increases effective network bandwidth.

Cisco NX-OS supports the Equal Cost Multiple Paths (ECMP) feature with up to 16 equal-cost paths in the EIGRP route table and the unicast RIB. You can configure EIGRP to load balance traffic across some or all of those paths.

Note EIGRP in Cisco NX-OS does not support unequal cost load balancing.

Split Horizon

You can use split horizon to ensure that EIGRP never advertises a route out of the interface where it was learned.

Split horizon is a method that controls the sending of EIGRP update and query packets. When you enable split horizon on an interface, Cisco NX-OS does not send update and query packets for destinations that were learned from this interface. Controlling update and query packets in this manner reduces the possibility of routing loops.

Split horizon with poison reverse configures EIGRP to advertise a learned route as unreachable back through that the interface that EIGRP learned the route from.

EIGRP uses split horizon or split horizon with poison reverse in the following scenarios:

- Exchanging topology tables for the first time between two routers in startup mode.

- Advertising a topology table change.

- Sending a Query message.

By default, the split horizon feature is enabled on all interfaces.

BFD

This feature supports bidirectional forwarding detection (BFD). BFD is a detection protocol designed to provide fast forwarding-path failure detection times. BFD provides subsecond failure detection between two adjacent devices and can be less CPU-intensive than protocol hello messages because some of the BFD load can be distributed onto the data plane on supported modules. See the Cisco Nexus 7000 Series NX-OS Interfaces Configuration Guide, Release 5.x, for more information.

Virtualization Support

Cisco NX-OS supports multiple instances of EIGRP that runs on the same system. EIGRP supports Virtual Routing and Forwarding instances (VRFs). VRFs exist within virtual device contexts (VDCs). By default, Cisco NX-OS places you in the default VDC and default VRF unless you specifically configure another VDC and VRF. See the Cisco Nexus 7000 Series NX-OS Virtual Device Context Configuration Guide, Release 5.x, and Chapter14, “Configuring Layer 3 Virtualization”

By default, every instance uses the same system router ID. You can optionally configure a unique router ID for each instance.

Graceful Restart and High Availability

Cisco NX-OS supports nonstop forwarding and graceful restart for EIGRP.

You can use nonstop forwarding for EIGRP to forward data packets along known routes in the FIB while the EIGRP routing protocol information is being restored following a failover. With nonstop forwarding (NSF), peer networking devices do not experience routing flaps. During failover, data traffic is forwarded through intelligent modules while the standby supervisor becomes active.

If a Cisco NX-OS system experiences a cold reboot, the device does not forward traffic to the system and removes the system from the network topology. In this scenario, EIGRP experiences a stateless restart, and all neighbors are removed. Cisco NX-OS applies the startup configuration, and EIGRP rediscovers the neighbors and shares the full EIGRP routing information again.

A dual supervisor platform that runs Cisco NX-OS can experience a stateful supervisor switchover. Before the switchover occurs, EIGRP uses a graceful restart to announce that EIGRP will be unavailable for some time. During a switchover, EIGRP uses nonstop forwarding to continue forwarding traffic based on the information in the FIB, and the system is not taken out of the network topology.

The graceful restart-capable router uses Hello messages to notify its neighbors that a graceful restart operation has started. When a graceful restart-aware router receives a notification from a graceful restart-capable neighbor that a graceful restart operation is in progress, both routers immediately exchange their topology tables. The graceful restart-aware router performs the following actions to assist the restarting router as follows:

- The router expires the EIGRP Hello hold timer to reduce the time interval set for Hello messages. This process allows the graceful restart-aware router to reply to the restarting router more quickly and reduces the amount of time required for the restarting router to rediscover neighbors and rebuild the topology table.

- The router starts the route-hold timer. This timer sets the period of time that the graceful restart-aware router will hold known routes for the restarting neighbor. The default time period is 240 seconds.

- The router notes in the peer list that the neighbor is restarting, maintains adjacency, and holds known routes for the restarting neighbor until the neighbor signals that it is ready for the graceful restart-aware router to send its topology table or the route-hold timer expires. If the route-hold timer expires on the graceful restart-aware router, the graceful restart-aware router discards held routes and treats the restarting router as a new router that joins the network and reestablishes adjacency.

After the switchover, Cisco NX-OS applies the running configuration, and EIGRP informs the neighbors that it is operational again.

Note You must enable graceful restart to support in-service software upgrades (ISSU) for EIGRP. If you disable graceful restart, Cisco NX-OS issues a warning that an ISSU cannot be supported with this configuration.

Licensing Requirements for EIGRP

Product

License Requirement

Cisco NX-OS

EIGRP requires an Enterprise Services license. For a complete explanation of the Cisco NX-OS licensing scheme and how to obtain and apply licenses, see the Cisco NX-OS Licensing Guide.

Prerequisites for EIGRP

EIGRP has the following prerequisites:

- You must enable EIGRP (see the “Enabling the EIGRP Feature” section).

- If you configure VDCs, install the Advanced Services license and enter the desired VDC (see the Cisco Nexus 7000 Series NX-OS Virtual Device Context Configuration Guide, Release 5.x).

Guidelines and Limitations for EIGRP

EIGRP has the following configuration guidelines and limitations:

- A metric configuration (either through the default-metric configuration option or through a route map) is required for redistribution from any other protocol, connected routes, or static routes (see Chapter 16, “Configuring Route Policy Manager”).

- For graceful restart, an NSF-aware router must be up and completely converged with the network before it can assist an NSF-capable router in a graceful restart operation.

- For graceful restart, neighboring devices participating in the graceful restart must be NSF-aware or NSF-capable.

- Cisco NX-OS EIGRP is compatible with EIGRP in the Cisco IOS software.

- Do not change the metric weights without a good reason. If you change the metric weights, you must apply the change to all EIGRP routers in the same autonomous system.

- A mix of standard metrics and wide metrics in an EIGRP network with interface speeds of 1 Gigabit or greater may result in suboptimal routing.

- Consider using stubs for larger networks.

- Avoid redistribution between different EIGRP autonomous systems because the EIGRP vector metric will not be preserved.

- The no { ip | ipv6 } next-hop-self command does not guarantee reachability of the next hop.

- The { ip | ipv6 } passive-interface eigrp command suppresses neighbors from forming.

- Cisco NX-OS does not support IGRP or connecting IGRP and EIGRP clouds.

- Autosummarization is disabled by default and cannot be enabled.

- Cisco NX-OS supports only IP.

Note If you are familiar with the Cisco IOS CLI, be aware that the Cisco NX-OS commands for this feature might differ from the Cisco IOS commands that you would use.

Default Settings

Table 8-1 Default EIGRP Parameters

Parameters

Default

Administrative distance

- Internal routes—90

- External routes—170

Bandwidth percent

50 percent

Default metric for redistributed routes

- Bandwidth—100000 Kb/s

- Delay—100 (10 microsecond units)

- Reliability—255

- Loading—1

- MTU—1500

EIGRP feature

Disabled

Hello interval

5 seconds

Hold time

15 seconds

Equal-cost paths

8

Metric weights

1 0 1 0 0 0

Next-hop address advertised

IP address of local interface

NSF convergence time

120

NSF route-hold time

240

NSF signal time

20

Redistribution

Disabled

Split horizon

Enabled

Configuring Basic EIGRP

This section includes the following topics:

- Enabling the EIGRP Feature

- Creating an EIGRP Instance

- Restarting an EIGRP Instance

- Shutting Down an EIGRP Instance

- Shutting Down EIGRP on an Interface

Enabling the EIGRP Feature

You must enable EIGRP before you can configure EIGRP.

BEFORE YOU BEGIN

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. feature eigrp

3. (Optional) show feature

4. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

feature eigrp

Example:

switch(config)# feature eigrp

Enables the EIGRP feature.

Step 3

show feature

Example:

switch(config)# show feature

(Optional) Displays information about enabled features.

Step 4

copy running-config startup-config

Example:

switch(config)# copy running-config startup-config

(Optional) Saves this configuration change.

To disable the EIGRP feature and remove all associated configuration, use the following command in configuration mode:

Command

Purpose

no feature eigrp

Example:

switch(config)# no feature eigrp

Disables the EIGRP feature and removes all associated configuration.

Creating an EIGRP Instance

You can create an EIGRP instance and associate an interface with that instance. You assign a unique autonomous system number for this EIGRP process (see the “Autonomous Systems” section). Routes are not advertised or accepted from other autonomous systems unless you enable route redistribution.

BEFORE YOU BEGIN

You must enable EIGRP (see the “Enabling the EIGRP Feature” section).

EIGRP must be able to obtain a router ID (for example, a configured loopback address) or you must configure the router ID option.

If you configure an instance tag that does not qualify as an AS number, you must configure the AS number explicitly or this EIGRP instance remains in the shutdown state. For IPv6, this number must be configured under address family.

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. router eigrp instance-tag

3. (Optional) autonomous-system as-number

4. (Optional) log-adjacency-changes

5. (Optional) log-neighbor-warnings [seconds]

6. interface interface-type slot/port

7. {ip | ipv6} router eigrp instance-tag

8. (Optional) show {ip | ipv6} eigrp interfaces

9. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

router eigrp instance-tag

Example:

switch(config)# router eigrp Test1

switch(config-router)#

Creates a new EIGRP process with the configured instance tag. The instance tag can be any case-sensitive, alphanumeric string up to 20 characters.

If you configure an instance-tag that does not qualify as an AS number, you must use the autonomous-system command to configure the AS number explicitly or this EIGRP instance will remain in the shutdown state.

Step 3

autonomous-system as-number

Example:

switch(config-router)# autonomous-system 33

(Optional) Configures a unique AS number for this EIGRP instance. The range is from 1 to 65535.

Step 4

log-adjacency-changes

Example:

switch(config-router)# log-adjacency-changes

(Optional). Generates a system message whenever an adjacency changes state. This command is enabled by default.

Step 5

log-neighbor-warnings [seconds]

Example:

switch(config-router)# log-neighbor-warnings

(Optional) Generates a system message whenever a neighbor warning occurs. You can configure the time between warning messages, from 1 to 65535, in seconds. The default is 10 seconds. This command is enabled by default.

Step 6

interface interface-type slot/port

Example:

switch(config-router)# interface ethernet 1/2

switch(config-if)#

Enters interface configuration mode. Use ? to determine the slot and port ranges.

Step 7

{ip | ipv6} router eigrp instance-tag

Example:

switch(config-if)# ip router eigrp Test1

Associates this interface with the configured EIGRP process. The instance tag can be any case-sensitive, alphanumeric string up to 20 characters.

Step 8

show {ip | ipv6} eigrp interfaces

Example:

switch(config-if)# show ip eigrp interfaces

(Optional) Displays information about EIGRP interfaces.

Step 9

copy running-config startup-config

Example:

switch(config)# copy running-config startup-config

(Optional) Saves this configuration change.

To remove the EIGRP process and the associated configuration, use the following command in the configuration mode:

Command

Purpose

no router eigrp instance-tag

Example:

switch(config)# no router eigrp Test1

Deletes the EIGRP process and all associated configuration.

Note You should also remove any EIGRP commands configured in interface mode if you remove the EIGRP process.

This example shows how to create an EIGRP process and configure an interface for EIGRP:

switch# configure terminal

switch(config)# router eigrp Test1

switch(config)# interface ethernet 1/2

switch(config-if)# ip router eigrp Test1

switch(config-if)# no shutdown

switch(config-if)# copy running-config startup-config

For more information about other EIGRP parameters, see the “Configuring Advanced EIGRP” section.

Restarting an EIGRP Instance

You can restart an EIGRP instance. This action clears all neighbors for the instance.

To restart an EIGRP instance and remove all associated neighbors, use the following commands:

Command

Purpose

flush-routes

Example:

switch(config)# flush-routes

(Optional) Flushes all EIGRP routes in the unicast RIB when this EIGRP instance restarts.

restart eigrp instance-tag

Example:

switch(config)# restart eigrp Test1

Restarts the EIGRP instance and removes all neighbors. The instance tag can be any case-sensitive, alphanumeric string up to 20 characters.

Shutting Down an EIGRP Instance

You can gracefully shut down an EIGRP instance. This action removes all routes and adjacencies but preserves the EIGRP configuration.

Command

Purpose

switch(config-router)# shutdown

Example:

switch(config-router)# shutdown

Disables this instance of EIGRP. The EIGRP router configuration remains.

Configuring a Passive Interface for EIGRP

You can configure a passive interface for EIGRP. A passive interface does not participate in EIGRP adjacency but the network address for the interface remains in the EIGRP topology table.

Command

Purpose

{ip | ipv6} passive-interface eigrp instance-tag

Example:

switch(config-if)# ip passive-interface eigrp tag10

Suppresses EIGRP hellos, which prevents neighbors from forming and sending routing updates on an EIGRP interface. The instance tag can be any case-sensitive, alphanumeric string up to 20 characters.

Shutting Down EIGRP on an Interface

You can gracefully shut down EIGRP on an interface. This action removes all adjacencies and stops EIGRP traffic on this interface but preserves the EIGRP configuration.

Command

Purpose

switch(config-if)# {ip | ipv6} eigrp instance-tag shutdown

Example:

switch(config-router)# ip eigrp Test1 shutdown

Disables EIGRP on this interface. The EIGRP interface configuration remains. The instance tag can be any case-sensitive, alphanumeric string up to 20 characters.

Configuring Advanced EIGRP

This section includes the following topics:

- Configuring Authentication in EIGRP

- Configuring EIGRP Stub Routing

- Configuring a Summary Address for EIGRP

- Redistributing Routes into EIGRP

- Limiting the Number of Redistributed Routes

- Configuring Load Balancing in EIGRP

- Configuring Graceful Restart for EIGRP

- Adjusting the Interval Between Hello Packets and the Hold Time

- Disabling Split Horizon

- Tuning EIGRP

Configuring Authentication in EIGRP

You can configure authentication between neighbors for EIGRP. See the “Authentication” section.

You can configure EIGRP authentication for the EIGRP process or for individual interfaces. The interface EIGRP authentication configuration overrides the EIGRP process-level authentication configuration.

BEFORE YOU BEGIN

You must enable EIGRP (see the “Enabling the EIGRP Feature” section).

Ensure that all neighbors for an EIGRP process share the same authentication configuration, including the shared authentication key.

Create the key chain for this authentication configuration. For more information, see the Cisco Nexus 7000 Series NX-OS Security Configuration Guide, Release 5.x.

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. router eigrp instance-tag

3. address-family {ipv4 | ipv6} unicast

4. authentication key-chain key-chain

5. authentication mode md5

6. interface interface-type slot/port

7. {ip | ipv6} router eigrp instance-tag

8. {ip | ipv6} authentication key-chain eigrp instance-tag key-chain

9. {ip | ipv6} authentication mode eigrp instance-tag md5

10. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

router eigrp instance-tag

Example:

switch(config)# router eigrp Test1

switch(config-router)#

Creates a new EIGRP process with the configured instance tag. The instance tag can be any case-sensitive, alphanumeric string up to 20 characters.

If you configure an instance-tag that does not qualify as an AS number, you must use the autonomous-system command to configure the AS number explicitly or this EIGRP instance will remain in the shutdown state.

Step 3

address-family {ipv4 | ipv6} unicast

Example:

switch(config-router)# address-family ipv4 unicast

switch(config-router-af)#

Enters the address-family configuration mode. This command is optional for IPv4.

Step 4

authentication key-chain key-chain

Example:

switch(config-router-af)# authentication key-chain routeKeys

Associates a key chain with this EIGRP process for this VRF. The key chain can be any case-sensitive, alphanumeric string up to 20 characters.

Step 5

authentication mode md5

Example:

switch(config-router-af)# authentication mode md5

Configures MD5 message digest authentication mode for this VRF.

Step 6

interface interface-type slot/port

Example:

switch(config-router-af) interface ethernet 1/2

switch(config-if)#

Enters interface configuration mode. Use ? to find the supported interfaces.

Step 7

{ip | ipv6} router eigrp instance-tag

Example:

switch(config-if)# ip router eigrp Test1

Associates this interface with the configured EIGRP process. The instance tag can be any case-sensitive, alphanumeric string up to 20 characters.

Step 8

{ip | ipv6} authentication key-chain eigrp instance-tag key-chain

Example:

switch(config-if)# ip authentication key-chain eigrp Test1 routeKeys

Associates a key chain with this EIGRP process for this interface. This configuration overrides the authentication configuration set in the router VRF mode.

The instance tag can be any case-sensitive, alphanumeric string up to 20 characters.

Step 9

{ip | ipv6} authentication mode eigrp instance-tag md5

Example:

switch(config-if)# ip authentication mode eigrp Test1 md5

Configures the MD5 message digest authentication mode for this interface. This configuration overrides the authentication configuration set in the router VRF mode.

The instance tag can be any case-sensitive, alphanumeric string up to 20 characters.

Step 10

copy running-config startup-config

Example:

switch(config)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to configure MD5 message digest authentication for EIGRP over Ethernet interface 1/2:

switch# configure terminal

switch(config)# router eigrp Test1

switch(config-router)# exit

switch(config)# interface ethernet 1/2

switch(config-if)# ip router eigrp Test1

switch(config-if)# ip authentication key-chain eigrp Test1 routeKeys

switch(config-if)# ip authentication mode eigrp Test1 md5

switch(config-if)# copy running-config startup-config

Configuring EIGRP Stub Routing

Command

Purpose

switch(config-router-af)# stub [direct | receive-only | redistributed [direct] leak-map map-name]

Example:

switch(config-router-af)# eigrp stub redistributed

Configures a remote router as an EIGRP stub router. The map name can be any case-sensitive, alphanumeric string up to 20 characters.

This example shows how to configure a stub router to advertise directly connected and redistributed routes:

switch# configure terminal

switch(config)# router eigrp Test1

switch(config-router)# address-family ipv6 unicast

switch(config-router-af)# stub direct redistributed

switch(config-router-af)# copy running-config startup-config

Use the show ip eigrp neighbor detail command to verify that a router has been configured as a stub router. The last line of the output shows the stub status of the remote or spoke router.

To configure a summary aggregate address, use the following command in interface configuration mode:

Command

Purpose

switch(config-if)# {ip | ipv6} summary-address eigrp instance-tag ip-prefix/length [distance | leak-map map-name]

Example:

switch(config-if)# ip summary-address eigrp Test1 192.0.2.0/8

Configures a summary aggregate address as either an IP address and network mask or an IP prefix/length. The instance tag and map name can be any case-sensitive, alphanumeric string up to 20 characters.

You can optionally configure the administrative distance for this aggregate address. The default administrative distance is 5 for aggregate addresses.

BEFORE YOU BEGIN

You must enable EIGRP (see the “Enabling the EIGRP Feature” section).

You must configure the metric (either through the default-metric configuration option or through a route map) for routes redistributed from any other protocol.

You must create a route map to control the types of routes that are redistributed into EIGRP. See Chapter16, “Configuring Route Policy Manager”

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. router eigrp instance-tag

3. address-family {ipv4 | ipv6} unicast

4. redistribute {bgp as | {eigrp | isis | ospf | ospfv3 | rip} instance-tag | direct | static} route-map name

5. default-metric bandwidth delay reliability loading mtu

6. (Optional) show {ip | ipv6} eigrp route-map statistics redistribute

7. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

router eigrp instance-tag

Example:

switch(config)# router eigrp Test1

switch(config-router)#

Creates a new EIGRP process with the configured instance tag. The instance tag can be any case-sensitive, alphanumeric string up to 20 characters.

If you configure an instance-tag that does not qualify as an AS number, you must use the autonomous-system command to configure the AS number explicitly or this EIGRP instance will remain in the shutdown state.

Step 3

address-family {ipv4 | ipv6} unicast

Example:

switch(config-router)# address-family ipv4 unicast

switch(config-router-af)#

Enters the address-family configuration mode. This command is optional for IPv4.

Step 4

redistribute {bgp as| {eigrp | isis | ospf | ospfv3 | rip} instance-tag | direct | static} route-map name

Example:

switch(config-router-af)# redistribute bgp 100 route-map BGPFilter

Injects routes from one routing domain into EIGRP. The instance tag and map name can be any case-sensitive, alphanumeric string up to 20 characters.

Step 5

default-metric bandwidth delay reliability loading mtu

Example:

switch(config-router-af)# default-metric 500000 30 200 1 1500

Sets the metrics assigned to routes learned through route redistribution. The default values are as follows:

- bandwidth—100000 Kb/s

- delay—100 (10 microsecond units)

- reliability—255

- loading—1

- MTU—1492

Step 6

show {ip | ipv6} eigrp route-map statistics redistribute

Example:

switch(config-router-af)# show ip eigrp route-map statistics redistribute bgp

(Optional) Displays information about EIGRP route map statistics.

Step 7

copy running-config startup-config

Example:

switch(config)# copy running-config startup-config

(Optional) Saves this configuration change.

The following example shows how to redistribute BGP into EIGRP for IPv4:

switch# configure terminal

switch(config)# router eigrp Test1

switch(config-router)# redistribute bgp 100 route-map BGPFilter

switch(config-router)# default-metric 500000 30 200 1 1500

switch(config-router)# copy running-config startup-config

Limiting the Number of Redistributed Routes

Route redistribution can add many routes to the EIGRP route table. You can configure a maximum limit to the number of routes accepted from external protocols. EIGRP provides the following options to configure redistributed route limits:

- Fixed limit—Logs a message when EIGRP reaches the configured maximum. EIGRP does not accept any more redistributed routes. You can optionally configure a threshold percentage of the maximum where EIGRP logs a warning when that threshold is passed.

- Warning only—Logs a warning only when EIGRP reaches the maximum. EIGRP continues to accept redistributed routes.

- Withdraw—Starts the timeout period when EIGRP reaches the maximum. After the timeout period, EIGRP requests all redistributed routes if the current number of redistributed routes is less than the maximum limit. If the current number of redistributed routes is at the maximum limit, EIGRP withdraws all redistributed routes. You must clear this condition before EIGRP accepts more redistributed routes. You can optionally configure the timeout period.

BEFORE YOU BEGIN

You must enable EIGRP (see the “Enabling the EIGRP Feature” section).

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. router eigrp instance-tag

3. redistribute {bgp id | direct | eigrp id | isis id | ospf id | rip id | static} route-map map-name

4. redistribute maximum-prefix max [threshold] [warning-only | withdraw [num-retries timeout]]

5. (Optional) show running-config eigrp

6. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

router eigrp instance-tag

Example:

switch(config)# router eigrp Test1

switch(config-router)#

Creates a new EIGRP instance with the configured instance tag.

Step 3

redistribute {bgp id | direct | eigrp id | isis id | ospf id | rip id | static} route-map map-name

Example:

switch(config-router)# redistribute bgp route-map FilterExternalBGP

Redistributes the selected protocol into EIGRP through the configured route map.

Step 4

redistribute maximum-prefix max [threshold] [warning-only | withdraw [num-retries timeout]]

Example:

switch(config-router)# redistribute maximum-prefix 1000 75 warning-only

Specifies a maximum number of prefixes that EIGRP distributes. The range is from 0 to 65536. Optionally specifies the following:

- threshold —Percent of maximum prefixes that triggers a warning message.

- warning-only —Logs an warning message when the maximum number of prefixes is exceeded.

- withdraw —Withdraws all redistributed routes. Optionally tries to retrieve the redistributed routes. The num-retries range is from 1 to 12. The timeout is from 60 to 600 seconds. The default is 300 seconds. Use the clear ip eigrp redistribution command if all routes are withdrawn.

Step 5

show running-config eigrp

Example:

switch(config-router)# show running-config eigrp

(Optional) Displays the EIGRP configuration.

Step 6

copy running-config startup-config

Example:

switch(config-router)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to limit the number of redistributed routes into EIGRP:

switch# configure terminal

switch(config)# router eigrp Test1

switch(config-router)# redistribute bgp route-map FilterExternalBGP

switch(config-router)# redistribute maximum-prefix 1000 75

Configuring Load Balancing in EIGRP

You can configure load balancing in EIGRP. You can configure the number of Equal Cost Multiple Path (ECMP) routes using the maximum paths option. See the “Configuring Load Balancing in EIGRP” section.

BEFORE YOU BEGIN

You must enable EIGRP (see the “Enabling the EIGRP Feature” section).

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. router eigrp instance-tag

3. address-family {ipv4 | ipv6} unicast

4. maximum-paths num-paths

5. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

router eigrp instance-tag

Example:

switch(config)# router eigrp Test1

switch(config-router)#

Creates a new EIGRP process with the configured instance tag. The instance tag can be any case-sensitive, alphanumeric string up to 20 characters.

If you configure an instance-tag that does not qualify as an AS number, you must use the autonomous-system command to configure the AS number explicitly or this EIGRP instance remains in the shutdown state.

Step 3

address-family {ipv4 | ipv6} unicast

Example:

switch(config-router)# address-family ipv4 unicast

switch(config-router-af)#

Enters the address-family configuration mode. This command is optional for IPv4.

Step 4

maximum-paths num-paths

Example:

switch(config-router-af)# maximum-paths 5

Sets the number of equal cost paths that EIGRP accepts in the route table. The range is from 1 to 16. The default is 8.

Step 5

copy running-config startup-config

Example:

switch(config-router-af)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to configure equal cost load balancing for EIGRP over IPv4 with a maximum of six equal cost paths:

switch# configure terminal

switch(config)# router eigrp Test1

switch(config-router)# maximum-paths 6

switch(config-router)# copy running-config startup-config

Configuring Graceful Restart for EIGRP

You can configure graceful restart or nonstop forwarding for EIGRP. See the “Graceful Restart and High Availability” section.

Note Graceful restart is enabled by default.

BEFORE YOU BEGIN

You must enable EIGRP (see the “Enabling the EIGRP Feature” section).

An NSF-aware router must be up and completely converged with the network before it can assist an NSF-capable router in a graceful restart operation.

Neighboring devices participating in the graceful restart must be NSF-aware or NSF-capable.

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. router eigrp instance-tag

3. address-family {ipv4 | ipv6} unicast

4. graceful-restart

5. timers nsf converge seconds

6. timers nsf route-hold seconds

7. timers nsf signal seconds

8. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

router eigrp instance-tag

Example:

switch(config)# router eigrp Test1

switch(config-router)#

Creates a new EIGRP process with the configured instance tag. The instance tag can be any case-sensitive, alphanumeric string up to 20 characters.

If you configure an instance-tag that does not qualify as an AS number, you must use the autonomous-system command to configure the AS number explicitly or this EIGRP instance remains in the shutdown state.

Step 3

address-family {ipv4 | ipv6} unicast

Example:

switch(config-router)# address-family ipv4 unicast

switch(config-router-af)#

Enters the address-family configuration mode. This command is optional for IPv4.

Step 4

graceful-restart

Example:

switch(config-router-af)# graceful-restart

Enables graceful restart. This feature is enabled by default.

Step 5

timers nsf converge seconds

Example:

switch(config-router-af)# timers nsf converge 100

Sets the time limit for the convergence after a switchover. The range is from 60 to 180 seconds. The default is 120.

Step 6

timers nsf route-hold seconds

Example:

switch(config-router-af)# timers nsf route-hold 200

Sets the hold time for routes learned from the graceful restart-aware peer. The range is from 20 to 300 seconds. The default is 240.

Step 7

timers nsf signal seconds

Example:

switch(config-router-af)# timers nsf signal 15

Sets the time limit for signaling a graceful restart. The range is from 10 to 30 seconds. The default is 20.

Step 8

copy running-config startup-config

Example:

switch(config-router-af)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to configure graceful restart for EIGRP over IPv6 using the default timer values:

switch# configure terminal

switch(config)# router eigrp Test1

switch(config-router)# address-family ipv6 unicast

switch(config-router-af)# graceful-restart

switch(config-router-af)# copy running-config startup-config

Adjusting the Interval Between Hello Packets and the Hold Time

You can adjust the interval between Hello messages and the hold time.

By default, Hello messages are sent every 5 seconds. The hold time is advertised in Hello messages and indicates to neighbors the length of time that they should consider the sender valid. The default hold time is three times the hello interval, or 15 seconds.

Command

Purpose

switch(config-if)# {ip | ipv6} hello-interval eigrp instance-tag seconds

Example:

switch(config-if)# ip hello-interval eigrp Test1 30

Configures the hello interval for an EIGRP routing process. The instance tag can be any case-sensitive, alphanumeric string up to 20 characters. The range is from 1 to 65535 seconds. The default is 5.

On very congested and large networks, the default hold time might not be sufficient time for all routers to receive hello packets from their neighbors. In this case, you might want to increase the hold time.

Command

Purpose

switch(config-if)# {ip | ipv6} hold-time eigrp instance-tag seconds

Example:

switch(config-if)# ipv6 hold-time eigrp Test1 30

Configures the hold time for an EIGRP routing process. The instance tag can be any case-sensitive, alphanumeric string up to 20 characters. The range is from 1 to 65535.

Use the show ip eigrp interface detail command to verify the timer configuration.

Disabling Split Horizon

You can use split horizon to block route information from being advertised by a router out of any interface from which that information originated. Split horizon usually optimizes communications among multiple routing devices, particularly when links are broken.

By default, split horizon is enabled on all interfaces.

Command

Purpose

switch(config-if)# no {ip | ipv6} split-horizon eigrp instance-tag

Example:

switch(config-if)# no ip split-horizon eigrp Test1

Disables split horizon.

Enabling Wide Metrics

To enable wide metrics, use the following command in router or address family configuration mode:

Command

Purpose

switch(config-router)# metrics version 64bit

Example:

switch(config-router)# metrics version 64bit

Enables 64-bit metric values.

To optionally configure a scaling factor for the RIB, use the following commands in router or address family configuration mode:

Command

Purpose

switch(config-router)# metrics rib-scale value

Example:

switch(config-router)# metrics rib-scale 128

(Optional) Configures the scaling factor used to convert the 64-bit metric values to 32 bit in the RIB. The range is from 1 to 255. The default is 128.

Tuning EIGRP

You can configure optional parameters to tune EIGRP for your network.

Command

Purpose

default-information originate [ always | route-map map-name ]

Example:

switch(config-router-af)# default-information originate always

Originates or accepts the default route with prefix 0.0.0.0/0. When a route-map is supplied, the default route is originated only when the route map yields a true condition. The map name can be any case-sensitive, alphanumeric string up to 20 characters.

distance internal external

Example:

switch(config-router-af)# distance 25 100

switch(config-router-af)# metric max-hops 70

switch(config-router-af)# metric weights 0 1 3 2 1 0

Adjusts the EIGRP metric or K value. EIGRP uses the following formula to determine the total metric to the network:

metric = [k1 x bandwidth + (k2 x bandwidth)/(256 – load) + k3 x delay + k6 x extended attributes] * [k5/(reliability + k4)]

Default values and ranges are as follows:

- TOS—0. The range is from 0 to 8.

- k1—1. The range is from 0 to 255.

- k2—0. The range is from 0 to 255.

- k3—1. The range is from 0 to 255.

- k4—0. The range is from 0 to 255.

- k5—0. The range is from 0 to 255.

- k6—0. The range is from 0 to 255.

timers active-time {time-limit | disabled}

Example:

switch(config-router-af)# timers active-time 200

Sets the time the router waits in minutes (after sending a query) before declaring the route to be stuck in the active (SIA) state. The range is from 1 to 65535. The default is 3.

You can configure the following optional parameters in interface configuration mode:

Command

Purpose

{ip | ipv6} bandwidth eigrp instance-tag bandwidth

Example:

switch(config-if)# ip bandwidth eigrp Test1 30000

Configures the bandwidth metric for EIGRP on an interface. The instance tag can be any case-sensitive, alphanumeric string up to 20 characters. The bandwidth range is from 1 to 2,560,000,000 Kb/s.

{ip | ipv6} bandwidth-percent eigrp instance-tag percent

Example:

switch(config-if)# ip bandwidth-percent eigrp Test1 30

Configures the percentage of bandwidth that EIGRP might use on an interface. The instance tag can be any case-sensitive, alphanumeric string up to 20 characters.

The percent range is from 0 to 100. The default is 50.

no {ip | ipv6} delay eigrp instance-tag delay

Example:

switch(config-if)# ip delay eigrp Test1 100

Configures the delay metric for EIGRP on an interface. The instance tag can be any case-sensitive, alphanumeric string up to 20 characters. The delay range is from 1 to 16777215 (in tens of microseconds).

{ ip | ipv6 } distribute-list eigrp instance-tag

{prefix-list name| route-map name} {in | out}

Example:

switch(config-if)# ip distribute-list eigrp Test1 route-map EigrpTest in

Configures the route filtering policy for EIGRP on this interface. The instance tag, prefix list name, and route map name can be any case-sensitive, alphanumeric string up to 20 characters.

no {ip | ipv6} next-hop-self eigrp instance-tag

Example:

switch(config-if)# ipv6 next-hop-self eigrp Test1

Configures EIGRP to use the received next-hop address rather than the address for this interface. The default is to use the IP address of this interface for the next-hop address. The instance tag can be any case-sensitive, alphanumeric string up to 20 characters.

{ip | ipv6} offset-list eigrp instance-tag {prefix-list name| route-map name} {in | out} offset

Example:

switch(config-if)# ip offset-list eigrp Test1 prefix-list EigrpList in

Adds an offset to incoming and outgoing metrics to routes learned by EIGRP. The instance tag, prefix list name, and route map name can be any case-sensitive, alphanumeric string up to 20 characters.

{ip | ipv6} passive-interface eigrp instance-tag

Example:

switch(config-if)# ip passive-interface eigrp Test1

Suppresses EIGRP hellos, which prevents neighbors from forming and sending routing updates on an EIGRP interface. The instance tag can be any case-sensitive, alphanumeric string up to 20 characters.

Configuring Virtualization for EIGRP

You can configure multiple EIGRP processes in each VDC. You can also create multiple VRFs within each VDC and use the same or multiple EIGRP processes in each VRF. You assign an interface to a VRF.

Note Configure all other parameters for an interface after you configure the VRF for an interface. Configuring a VRF for an interface deletes all other configuration for that interface.

BEFORE YOU BEGIN

You must enable EIGRP (see the “Enabling the EIGRP Feature” section).

Create the VDCs and VRFs.

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. vrf context vrf-name

3. router eigrp instance-tag

4. interface ethernet slot/port

5. vrf member vrf-name

6. {ip | ipv6} router eigrp instance-tag

7. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

vrf context vrf-name

Example:

switch(config)# vrf context RemoteOfficeVRF

switch(config-vrf)#

Creates a new VRF and enters VRF configuration mode. The VRF name can be any case-sensitive, alphanumeric string up to 20 characters.

Step 3

router eigrp instance-tag

Example:

switch(config)# router eigrp Test1

switch(config-router)#

Creates a new EIGRP process with the configured instance tag. The instance tag can be any case-sensitive, alphanumeric string up to 20 characters.

If you configure an instance-tag that does not qualify as an AS number, you must use the autonomous-system command to configure the AS number explicitly or this EIGRP instance remains in the shutdown state.

Step 4

interface ethernet slot/port

Example:

switch(config)# interface ethernet 1/2

switch(config-if)#

Enters interface configuration mode. Use ? to find the slot and port ranges.

Step 5

vrf member vrf-name

Example:

switch(config-if)# vrf member RemoteOfficeVRF

Adds this interface to a VRF. The VRF name can be any case-sensitive, alphanumeric string up to 20 characters.

Step 6

{ip | ipv6} router eigrp instance-tag

Example:

switch(config-if)# ip router eigrp Test1

Adds this interface to the EIGRP process. The instance tag can be any case-sensitive, alphanumeric string up to 20 characters.

Step 7

copy running-config startup-config

Example:

switch(config-if)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to create a VRF and add an interface to the VRF:

switch# configure terminal

switch(config)# vrf context NewVRF

switch(config-vrf)# router eigrp Test1

switch(config-router)# interface ethernet 1/2

switch(config-if)# ip router eigrp Test1

switch(config-if)# vrf member NewVRF

switch(config-if)# copy running-config startup-config

Verifying the EIGRP Configuration

Command

Purpose

show {ip | ipv6} eigrp [instance-tag]

Displays a summary of the configured EIGRP processes.

show {ip | ipv6} eigrp [instance-tag] interfaces [type number] [brief] [detail]

Displays information about all configured EIGRP interfaces.

show {ip | ipv6} eigrp instance-tag neighbors [type number] [detail]

Displays information about all the EIGRP neighbors. Use this command to verify the EIGRP neighbor configuration.

show {ip | ipv6} eigrp [instance-tag] route [ip-prefix/length] [active] [all-links] [detail-links] [pending] [summary] [zero-successors] [vrf vrf-name]

Displays information about all the EIGRP routes.

show {ip | ipv6} eigrp [instance-tag] topology [ip-prefix/length] [active] [all-links] [detail-links] [pending] [summary] [zero-successors] [vrf vrf-name]

Displays information about the EIGRP topology table.

show running-configuration eigrp

Displays the current running EIGRP configuration.

Monitoring EIGRP

Command

Purpose

show {ip | ipv6} eigrp [instance-tag] accounting [vrf vrf-name]

Displays accounting statistics for EIGRP.

show {ip | ipv6} eigrp [instance-tag] route-map statistics redistribute

Displays redistribution statistics for EIGRP.

show {ip | ipv6} eigrp [instance-tag] traffic [vrf vrf-name]

Displays traffic statistics for EIGRP.

Configuration Examples for EIGRP

Additional References

For additional information related to implementing EIGRP, see the following sections:

- Related Documents

Related Documents

Related Topic

Document Title

EIGRP CLI commands

Cisco Nexus 7000 Series NX-OS Unicast Routing Command Reference, Release 5.x

VDCs and VRFs

Cisco Nexus 7000 Series NX-OS Virtual Device Context Configuration Guide, Release 5.x

http://www.cisco.com/warp/public/103/1.html

Introduction to EIGRP Tech Note

http://www.cisco.com/en/US/tech/tk365/technologies_q_and_a_item09186a008012dac4.shtml

EIGRP Frequently Asked Questions

MIBs

MIBs

MIBs Link

CISCO-EIGRP-MIB

To locate and download MIBs, go to the following URL:

http://www.cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml

Feature History for EIGRP

Table 8-2 Feature History for EIGRP

Feature Name

Releases

Feature Information

Wide metrics

5.2(1)

Added support for EIGRP wide metrics.

BFD

5.0(2)

Added support for BFD. See the Cisco Nexus 7000 Series NX-OS Interfaces Configuration Guide, Release 5.x, for more information.

Graceful shutdown

4.2(1)

Added support to gracefully shut down an EIGRP instance or EIGRP on an interface but preserve the EGIRP configuration.

EIGRP instance tag

4.2(1)

Changed length to 20 characters.

Limits on redistributed routes

4.2(1)

Added support for limiting the number of redistributed routes.

EIGRP IPv6 support

4.1(2)

Added support for IPv6.

Authentication

4.0(3)

Added the ability to configure authentication within a VRF for EIGRP.

EIGRP

4.0(1)

Configuring HSRP

This chapter describes how to configure the Hot Standby Router Protocol (HSRP) on the Cisco NX-OS device.

This chapter includes the following sections:

- Information About HSRP

- Licensing Requirements for HSRP

- Prerequisites for HSRP

- Guidelines and Limitations for HSRP

- Default Settings

- Configuring HSRP

- Verifying the HSRP Configuration

- Configuration Examples for HSRP

- Additional References

- Feature History for HSRP

Information About HSRP

HSRP is a first-hop redundancy protocol (FHRP) that allows a transparent failover of the first-hop IP router. HSRP provides first-hop routing redundancy for IP hosts on Ethernet networks configured with a default router IP address. You use HSRP in a group of routers for selecting an active router and a standby router. In a group of routers, the active router is the router that routes packets; the standby router is the router that takes over when the active router fails or when preset conditions are met.

Many host implementations do not support any dynamic router discovery mechanisms but can be configured with a default router. Running a dynamic router discovery mechanism on every host is not practical for many reasons, including administrative overhead, processing overhead, and security issues. HSRP provides failover services to these hosts.

This section includes the following topics:

- HSRP Overview

- HSRP for IPv4

- HSRP for IPv6

- HSRP Versions

- HSRP Authentication

- HSRP Messages

- HSRP Load Sharing

- Object Tracking and HSRP

- vPC and HSRP

- BFD

- High Availability and Extended Nonstop Forwarding

- Virtualization Support

HSRP Overview

When you use HSRP, you configure the HSRP virtual IP address as the host’s default router (instead of the IP address of the actual router). The virtual IP address is an IPv4 or IPv6 address that is shared among a group of routers that run HSRP.

When you configure HSRP on a network segment, you provide a virtual MAC address and a virtual IP address for the HSRP group. You configure the same virtual address on each HSRP-enabled interface in the group. You also configure a unique IP address and MAC address on each interface that acts as the real address. HSRP selects one of these interfaces to be the active router. The active router receives and routes packets destined for the virtual MAC address of the group.

HSRP detects when the designated active router fails. At that point, a selected standby router assumes control of the virtual MAC and IP addresses of the HSRP group. HSRP also selects a new standby router at that time.

HSRP uses a priority designator to determine which HSRP-configured interface becomes the default active router. To configure an interface as the active router, you assign it with a priority that is higher than the priority of all the other HSRP-configured interfaces in the group. The default priority is 100, so if you configure just one interface with a higher priority, that interface becomes the default active router.

Interfaces that run HSRP send and receive multicast User Datagram Protocol (UDP)-based hello messages to detect a failure and to designate active and standby routers. When the active router fails to send a hello message within a configurable period of time, the standby router with the highest priority becomes the active router. The transition of packet forwarding functions between the active and standby router is completely transparent to all hosts on the network.

You can configure multiple HSRP groups on an interface.

Figure 19-1 shows a network configured for HSRP. By sharing a virtual MAC address and a virtual IP address, two or more interfaces can act as a single virtual router.

Figure 19-1 HSRP Topology with Two Enabled Routers

The virtual router does not physically exist but represents the common default router for interfaces that are configured to provide backup to each other. You do not need to configure the hosts on the LAN with the IP address of the active router. Instead, you configure them with the IP address of the virtual router (virtual IP address) as their default router. If the active router fails to send a hello message within the configurable period of time, the standby router takes over, responds to the virtual addresses, and becomes the active router, assuming the active router duties. From the host perspective, the virtual router remains the same.

Note Packets received on a routed port destined for the HSRP virtual IP address terminate on the local router, regardless of whether that router is the active HSRP router or the standby HSRP router. This includes ping and Telnet traffic. Packets received on a Layer 2 (VLAN) interface destined for the HSRP virtual IP address terminate on the active router.

HSRP for IPv4

HSRP routers communicate with each other by exchanging HSRP hello packets. These packets are sent to the destination IP multicast address 224.0.0.2 (reserved multicast address used to communicate to all routers) on UDP port 1985. The active router sources hello packets from its configured IP address and the HSRP virtual MAC address while the standby router sources hellos from its configured IP address and the interface MAC address, which might be the burned-in address (BIA). The BIA is the last six bytes of the MAC address that is assigned by the manufacturer of the network interface card (NIC).

Because hosts are configured with their default router as the HSRP virtual IP address, hosts must communicate with the MAC address associated with the HSRP virtual IP address. This MAC address is a virtual MAC address, 0000.0C07.ACxy, where xy is the HSRP group number in hexadecimal based on the respective interface. For example, HSRP group 1 uses the HSRP virtual MAC address of 0000.0C07.AC01. Hosts on the adjoining LAN segment use the normal Address Resolution Protocol (ARP) process to resolve the associated MAC addresses.

HSRP version 2 uses the new IP multicast address 224.0.0.102 to send hello packets instead of the multicast address of 224.0.0.2, which is used by version 1. HSRP version 2 permits an expanded group number range of 0 to 4095 and uses a new MAC address range of 0000.0C9F.F000 to 0000.0C9F.FFFF.

HSRP for IPv6

IPv6 hosts learn of available IPv6 routers through IPv6 neighbor discovery (ND) router advertisement (RA) messages. These messages are multicast periodically, or might be solicited by hosts, but the time delay for detecting when a default route is down might be 30 seconds or more. HSRP for IPv6 provides a much faster switchover to an alternate default router than the IPv6 ND protocol provides, less than a second if the milliseconds timers are used. HSRP for IPv6 provides a virtual first hop for IPv6 hosts.

When you configure an IPv6 interface for HSRP, the periodic RAs for the interface link-local address stop after IPv6 ND sends a final RA with a router lifetime of zero. No restrictions occur for the interface IPv6 link-local address. Other protocols continue to receive and send packets to this address.

IPv6 ND sends periodic RAs for the HSRP virtual IPv6 link-local address when the HSRP group is active. These RAs stop after a final RA is sent with a router lifetime of 0 when the HSRP group leaves the active state. HSRP uses the virtual MAC address for active HSRP group messages only (hello, coup, and redesign).

HSRP for IPv6 uses the following parameters:

- HSRP version 2

- UDP port 2029

- Virtual MAC address range from 0005.73A0.0000 through 0005.73A0.0FFF

- Multicast link-local IP destination address of FF02::66

- Hop limit set to 255

HSRP IPv6 Addresses

An HSRP IPv6 group has a virtual MAC address that is derived from the HSRP group number and a virtual IPv6 link-local address that is derived, by default, from the HSRP virtual MAC address. The default virtual MAC address for an HSRP IPv6 group is always used to form the virtual IPv6 link-local address, regardless of the actual virtual MAC address used by the group.

Table 19-1 HSRP and IPv6 ND Addresses

Packet

MAC Source Address

IPv6 Source Address

IPv6 Destination Address

Link-layer Address Option

Neighbor solicitation (NS)

Interface MAC address

Interface IPv6 address

—

Interface MAC address

Router solicitation (RS)

Interface MAC address

Interface IPv6 address

—

Interface MAC address

Neighbor advertisement (NA)

Interface MAC address

Interface IPv6 address

Virtual IPv6 address

HSRP virtual MAC address

Route advertisement (RA)

Interface MAC address

Virtual IPv6 address

—

HSRP virtual MAC address

HSRP (inactive)

Interface MAC address

Interface IPv6 address

—

—

HSRP (active)

Virtual MAC address

Interface IPv6 address

—

—

HSRP does not add IPv6 link-local addresses to the Unicast Routing Information Base (URIB). There are also no secondary virtual IP addresses for link-local addresses.

For global unicast addresses, HSRP adds the virtual IPv6 address to the URIB and IPv6, but does not register the virtual IPv6 addresses to ICMPv6. ICMPv6 redirects are not supported for HSRP IPv6 groups.

HSRP Versions

Cisco NX-OS supports HSRP version 1 by default. You can configure an interface to use HSRP version 2.

HSRP version 2 has the following enhancements to HSRP version 1:

- Expands the group number range. HSRP version 1 supports group numbers from 0 to 255. HSRP version 2 supports group numbers from 0 to 4095.

- For IPv4, uses the IPv4 multicast address 224.0.0.102 or the IPv6 multicast address FF02::66 to send hello packets instead of the multicast address of 224.0.0.2, which is used by HSRP version 1.

- Uses the MAC address range from 0000.0C9F.F000 to 0000.0C9F.FFFF for IPv4 and 0005.73A0.0000 through 0005.73A0.0FFF for IPv6 addresses. HSRP version 1 uses the MAC address range 0000.0C07.AC00 to 0000.0C07.ACFF.

- Adds support for MD5 authentication.

When you change the HSRP version, Cisco NX-OS reinitializes the group because it now has a new virtual MAC address.

HSRP version 2 has a different packet format than HSRP version 1. The packet format uses a type-length-value (TLV) format. HSRP version 2 packets received by an HSRP version 1 router are ignored.

HSRP Authentication

HSRP message digest 5 (MD5) algorithm authentication protects against HSRP-spoofing software and uses the industry-standard MD5 algorithm for improved reliability and security. HSRP includes the IPv4 or IPv6 address in the authentication TLVs.

HSRP Messages

Routers that are configured with HSRP exchange the following three types of multicast messages:

- Hello—The hello message conveys the HSRP priority and state information of the router to other HSRP routers.

- Coup—When a standby router wants to assume the function of the active router, it sends a coup message.

- Resign—A router that is the active router sends this message when it is about to shut down or when a router that has a higher priority sends a hello or coup message.

HSRP Load Sharing

HSRP allows you to configure multiple groups on an interface. You can configure two overlapping IPv4 HSRP groups to load share traffic from the connected hosts while providing the default router redundancy expected from HSRP. Figure 19-2 shows an example of a load-sharing HSRP IPv4 configuration.

Figure 19-2 HSRP Load Sharing

Figure 19-2 shows two routers A and B and two HSRP groups. Router A is the active router for group A but is the standby router for group B. Similarly, router B is the active router for group B and the standby router for group A. If both routers remain active, HSRP load balances the traffic from the hosts across both routers. If either router fails, the remaining router continues to process traffic for both hosts.

Note HSRP for IPv6 load-balances by default. If there are two HSRP IPv6 groups on the subnet, then hosts learn of both groups from their router advertisements and choose to use one so that the load is shared between the advertised routers.

Object Tracking and HSRP

You can use object tracking to modify the priority of an HSRP interface based on the operational state of another interface. Object tracking allows you to route to a standby router if the interface to the main network fails.

Two objects that you can track are the line protocol state of an interface or the reachability of an IP route. If the specified object goes down, Cisco NX-OS reduces the HSRP priority by the configured amount. For more information, see the “Configuring HSRP Object Tracking” section.

vPC and HSRP

HSRP interoperates with virtual port channels (vPCs). vPCs allow links that are physically connected to two different Cisco Nexus 7000 Series devices to appear as a single port channel by a third device. See the Cisco Nexus 7000 Series NX-OS Layer 2 Switching Configuration Guide, Release 5.x, for more information on vPCs.

vPC forwards traffic through both the active HSRP router and the standby HSRP router. For more information, see the “Configuring the HSRP Priority” section and the “Configuration Examples for HSRP” section.

Note You should configure HSRP on the primary vPC peer device as active and HSRP on the vPC secondary device as standby.

vPC Peer Gateway and HSRP

Some third-party devices can ignore the HSRP virtual MAC address and instead use the source MAC address of an HSRP router. in a vPC environment, the packets using this source MAC address may be sent across the vPC peer link, causing a potential dropped packet. Configure the vPC peer gateway to enable the HSRP routers to directly handle packets sent to the local vPC peer MAC address and the remote vPC peer MAC address, as well as the HSRP virtual MAC address. See the Cisco Nexus 7000 Series NX-OS Layer 2 Switching Configuration Guide, Release 5.x, for more information on the vPC peer gateway.

Note For mixed-chassis configurations where the vPC peer link is configured on an F-series module, configure the vPC peer gateway exclude option to exclude the Layer 3 backup route that traverses the vPC peer link. See the Cisco Nexus 7000 Series NX-OS Layer 2 Switching Configuration Guide, Release 5.x, for more information on the vPC peer gateway exclude option.

BFD

This feature supports bidirectional forwarding detection (BFD). BFD is a detection protocol that provides fast-forwarding and path-failure detection times. BFD provides subsecond failure detection between two adjacent devices and can be less CPU-intensive than protocol hello messages because some of the BFD load can be distributed onto the data plane on supported modules. See the Cisco Nexus 7000 Series NX-OS Interfaces Configuration Guide, Release 5.x, for more information.

High Availability and Extended Nonstop Forwarding

HSRP supports stateful restarts and stateful switchovers. A stateful restart occurs when the HSRP process fails and is restarted. A stateful switchover occurs when the active supervisor switches to the standby supervisor. Cisco NX-OS applies the run-time configuration after the switchover.

If HSRP hold timers are configured for short time periods, these timers might expire during a controlled switchover or in-service software upgrade (ISSU). HSRP supports extended non-stop forwarding (NSF) to temporarily extend these HSRP hold timers during a controlled switchover or ISSU.

With extended NSF configured, HSRP sends hello messages with the extended timers. HSRP peers update their hold timers with these new values. The extended timers prevent unnecessary HSRP state changes during the switchover or ISSU. After the switchover or ISSU event, HSRP restores the hold timers to their original configured values. If the switchover fails, HSRP restores the hold timers after the extended hold timer values expire.

See the “Configuring Extended Hold Timers for HSRP” section for more information.

Virtualization Support

HSRP supports virtual routing and forwarding (VRF) instances. VRFs exist within virtual device contexts (VDCs). By default, Cisco NX-OS places you in the default VDC and default VRF unless you specifically configure another VDC and VRF.

If you change the VRF membership of an interface, Cisco NX-OS removes all Layer 3 configuration, including HSRP.

For more information, see the Cisco Nexus 7000 Series NX-OS Virtual Device Context Configuration Guide, Release 5.x, and see Chapter14, “Configuring Layer 3 Virtualization”

Licensing Requirements for HSRP

Product

License Requirement

Cisco NX-OS

HSRP requires no license. Any feature not included in a license package is bundled with the Cisco NX-OS system images and is provided at no extra charge to you. For a complete explanation of the Cisco NX-OS licensing scheme, see the Cisco NX-OS Licensing Guide.

Prerequisites for HSRP

- You must enable the HSRP feature in a device before you can configure and enable any HSRP groups.

- If you configure VDCs, install the Advanced Services license and enter the desired VDC (see the Cisco Nexus 7000 Series NX-OS Virtual Device Context Configuration Guide, Release 5.x).

Guidelines and Limitations for HSRP

HSRP has the following configuration guidelines and limitations:

- You must configure an IP address for the interface that you configure HSRP on and enable that interface before HSRP becomes active.

- You must configure HSRP version 2 when you configure an IPv6 interface for HSRP.

- For IPv4, the virtual IP address must be in the same subnet as the interface IP address.

- The value of the first 2 digits of a type 7 key string configured by using the key-string 7 text-string command has to be between 0 and 15. For example, you can configure 07372b557e2c1a as the key string value in which case the sum value of the first 2 digits will be 7. But, you cannot configure 85782916342021 as the key string value because the value of the first 2 digits will be 85. We recommend unconfiguring any type 7 key strings that do not adhere to this value or to configure a type 0 string.

- We recommend that you do not configure more than one first-hop redundancy protocol on the same interface.

- HSRP version 2 does not interoperate with HSRP version 1. An interface cannot operate both version 1 and version 2 because both versions are mutually exclusive. However, the different versions can be run on different physical interfaces of the same router.

- You cannot change from version 2 to version 1 if you have configured groups above the group number range allowed for version 1 (0 to 255).

- HSRP for IPv4 is supported with BFD. HSRP for IPv6 is not supported with BFD.

- Cisco NX-OS removes all Layer 3 configurations on an interface when you change the interface VRF membership, port channel membership, or when you change the port mode to Layer 2.

- If you configure virtual MAC addresses with vPC, you must configure the same virtual MAC address on both vPC peers.

- For mixed-chassis configurations where the vPC peer link is configured on an F-series module, configure the vPC peer gateway exclude option to exclude the Layer 3 backup route that traverses the vPC peer link.

- You cannot use the HSRP MAC address burned-in option on a VLAN interface that is a vPC member.

- If you have not configured authentication, the show hsrp command displays the following string:

Authentication text "cisco"

This is the default behavior of HSRP as defined in RFC 2281:

If no authentication data is configured, the RECOMMENDED default

value is 0x63 0x69 0x73 0x63 0x6F 0x00 0x00 0x00.

Default Settings

Table 19-2 Default HSRP Parameters

Parameters

Default

HSRP

Disabled

Authentication

Enabled as text for version 1, with cisco as the password

HSRP version

Version 1

Preemption

Disabled

Priority

100

Virtual MAC address

Derived from HSRP group number

Configuring HSRP

This section includes the following topics:

- Enabling HSRP

- Configuring the HSRP Version

- Configuring an HSRP Group for IPv4

- Configuring an HSRP Group for IPv6

- Configuring the HSRP Virtual MAC Address

- Authenticating HSRP

- Configuring HSRP Object Tracking

- Configuring the HSRP Priority

- Customizing HSRP

- Configuring Extended Hold Timers for HSRP

Note If you are familiar with the Cisco IOS CLI, be aware that the Cisco NX-OS commands for this feature might differ from the Cisco IOS commands that you would use.

Enabling HSRP

You must globally enable HSRP before you can configure and enable any HSRP groups.

BEFORE YOU BEGIN

Ensure that you are in the correct VDC (or use the switchto vdc command).

DETAILED STEPS

Command

Purpose

feature hsrp

Example:

switch(config)# feature hsrp

Enables HSRP.

To disable the HSRP feature in a VDC and remove all associated configurations, use the following command in global configuration mode:

Command

Purpose

no feature hsrp

Example:

switch(config)# no feature hsrp

Disables HSRP for all groups in a VDC.

Configuring the HSRP Version

You can configure the HSRP version. If you change the version for existing groups, Cisco NX-OS reinitializes HSRP for those groups because the virtual MAC address changes. The HSRP version applies to all groups on the interface.

Note IPv6 HSRP groups must be configured as HSRP version 2.

Command

Purpose

hsrp version {1 | 2}

Example:

switch(config-if)# hsrp version 2

Configures the HSRP version. Version 1 is the default.

Configuring an HSRP Group for IPv4

You can configure an HSRP group on an IPv4 interface and configure the virtual IP address and virtual MAC address for the HSRP group.

BEFORE YOU BEGIN

Ensure that you have enabled the HSRP feature (see the “Enabling HSRP” section).

Cisco NX-OS enables an HSRP group once you configure the virtual IP address on any member interface in the group. You should configure HSRP attributes such as authentication, timers, and priority before you enable the HSRP group.

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. interface type number

3. ip ip-address/length

4. hsrp group-number [ipv4]

5. ip [ip-address [secondary]]

6. exit

7. no shutdown

8. (Optional) show hsrp [group group-number] [ipv4]

9. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

interface type number

Example:

switch(config)# interface ethernet 1/2

switch(config-if)#

Enters interface configuration mode.

Step 3

ip ip-address/length

Example:

switch(config-if)# ip 192.0.2.2/8

Configures the IPv4 address of the interface.

Step 4

hsrp group-number [ipv4]

Example:

switch(config-if)# hsrp 2

switch(config-if-hsrp)#

Creates an HSRP group and enters hsrp configuration mode. The range for HSRP version 1 is from 0 to 255. The range is for HSRP version 2 is from 0 to 4095. The default value is 0.

Step 5

ip [ip-address [secondary]]

Example:

switch(config-if-hsrp)# ip 192.0.2.1

Configures the virtual IP address for the HSRP group and enables the group. This address should be in the same subnet as the IPv4 address of the interface.

Step 6

exit

Example:

switch(config-if-hsrp)# exit

Exits HSRP configuration mode.

Step 7

no shutdown

Example:

switch(config-if)# no shutdown

Enables the interface.

Step 8

show hsrp [group group-number] [ipv4]

Example:

switch(config-if)# show hsrp group 2

(Optional) Displays HSRP information.

Step 9

copy running-config startup-config

Example:

switch(config-if)# copy running-config startup-config

Note You should use the no shutdown command to enable the interface after you finish the configuration.

The following example shows how to configure an HSRP group on Ethernet 1/2:

switch# configure terminal

switch(config)# interface ethernet 1/2

switch(config-if)# ip 192.0.2.2/8

switch(config-if)# hsrp 2

switch(config-if-hsrp)# ip 192.0.2.1

switch(config-if-hsrp)# exit

switch(config-if)# no shutdown

switch(config-if)# copy running-config startup-config

Configuring an HSRP Group for IPv6

You can configure an HSRP group on an IPv6 interface and configure the virtual MAC address for the HSRP group.

When you configure an HSRP group for IPv6, HSRP generates a link-local address from the link-local prefix. HSRP also generates a modified EUI-64 format interface identifier in which the EUI-64 interface identifier is created from the relevant HSRP virtual MAC address.

There are no HSRP IPv6 secondary addresses.

BEFORE YOU BEGIN

You must enable HSRP (see the “Enabling HSRP” section).

Ensure that you have enabled HSRP version 2 on the interface that you want to configure an IPv6 HSRP group on.

Ensure that you have configured HSRP attributes such as authentication, timers, and priority before you enable the HSRP group.

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. interface type number

3. ipv6 address ipv6-address/length

4. hsrp version 2

5. hsrp group-number ipv6

6. ip [ipv6-address [secondary]]

7. ip autoconfig

8. no shutdown

9. (Optional) show hsrp [group group-number] [ipv6]

10. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

interface type number

Example:

switch(config)# interface ethernet 3/2

switch(config-if)#

Enters interface configuration mode.

Step 3

ipv6 address ipv6-address/length

Example:

switch(config-if)# ipv6 address 2001:0DB8:0001:0001:/64

Configures the IPv6 address of the interface.

Step 4

hsrp version 2

Example:

switch(config-if-hsrp)# hsrp version 2

Configures this group for HSRP version 2.

Step 5

hsrp group-number ipv6

Example:

switch(config-if)# hsrp 10 ipv6

switch(config-if-hsrp)#

Creates an IPv6 HSRP group and enters hsrp configuration mode. The range for HSRP version 2 is from 0 to 4095. The default value is 0.

Step 6

ip [ipv6-address [secondary]]

Example:

switch(config-if-hsrp)# ip 2001:DB8::1

Configures the virtual IPv6 address for the HSRP group and enables the group.

Step 7

ip autoconfig

Example:

switch(config-if-hsrp)# ip autoconfig

Autoconfigures the virtual IPv6 address for the HSRP group from the calculated link-local virtual IPv6 address and enables the group.

Step 8

no shutdown

Example:

switch(config-if-hsrp)# no shutdown

Enables the interface.

Step 9

show hsrp [group group-number] [ipv6]

Example:

switch(config-if-hsrp)# show hsrp group 10

(Optional) Displays HSRP information.

Step 10

copy running-config startup-config

Example:

switch(config-if-hsrp)# copy running-config startup-config

Note You should use the no shutdown command to enable the interface after you finish the configuration.

This example shows how to configure an IPv6 HSRP group on Ethernet 3/2:

switch# configure terminal

switch(config)# interface ethernet 3/2

switch(config-if)# ipv6 address 2001:0DB8:0001:0001:/64

switch(config-if)# hsrp 2 ipv6

switch(config-if-hsrp)# exit

switch(config-if)# no shutdown

switch(config-if)# copy running-config startup-config

Configuring the HSRP Virtual MAC Address

You can override the default virtual MAC address that HSRP derives from the configured group number.

Note You must configure the same virtual MAC address on both vPC peers of a vPC link.

Command

Purpose

mac-address string

Example:

switch(config-if-hsrp)# mac-address 5000.1000.1060

Configures the virtual MAC address for an HSRP group. The string uses the standard MAC address format (xxxx.xxxx.xxxx).

To configure HSRP to use the burned-in MAC address of the interface for the virtual MAC address, use the following command in interface configuration mode:

Command

Purpose

hsrp use-bia [scope interface]

Example:

switch(config-if)# hsrp use-bia

Configures HSRP to use the burned-in MAC address of the interface for the HSRP virtual MAC address. You can optionally configure HSRP to use the burned-in MAC address for all groups on this interface by using the scope interface keyword.

Authenticating HSRP

You can configure HSRP to authenticate the protocol using cleartext or MD5 digest authentication. MD5 authentication uses a key chain (see the Cisco Nexus 7000 Series NX-OS Security Configuration Guide, Release 5.x).

BEFORE YOU BEGIN

You must enable HSRP (see the “Enabling HSRP” section).

You must configure the same authentication and keys on all members of the HSRP group.

Ensure that you have created the key chain if you are using MD5 authentication.

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. interface interface-type slot/port

3. hsrp group-number [ipv4 | ipv6]

4. authentication text string

or

authentication md5 {key-chain key-chain | key-string {0 | 7} text [timeout seconds]}

5. (Optional) show hsrp [group group-number]

6. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

interface interface-type slot/port

Example:

switch(config)# interface ethernet 1/2

switch(config-if)#

Enters interface configuration mode.

Step 3

hsrp group-number [ipv4 | ipv6]

Example:

switch(config-if)# hsrp 2

switch(config-if-hsrp)#

Creates an HSRP group and enters HSRP configuration mode.

Step 4

authentication text string

Example:

switch(config-if-hsrp)# authentication text mypassword

Configures cleartext authentication for HSRP on this interface.

authentication md5 {key-chain key-chain | key-string {0 | 7} text [timeout seconds]}

Example:

switch(config-if-hsrp)# authentication md5 key-chain hsrp-keys

Configures MD5 authentication for HSRP on this interface. You can use a key chain or key string. If you use a key string, you can optionally set the timeout for when HSRP only accepts a new key. The range is from 0 to 32767 seconds.

Step 5

show hsrp [group group-number]

Example:

switch(config-if-hsrp)# show hsrp group 2

(Optional) Displays HSRP information.

Step 6

copy running-config startup-config

Example:

switch(config-if-hsrp)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to configure MD5 authentication for HSRP on Ethernet 1/2 after creating the key chain:

switch# configure terminal

switch(config)# key chain hsrp-keys

switch(config-keychain)# key 0

switch(config-keychain-key)# key-string 7 zqdest

switch(config-keychain-key) accept-lifetime 00:00:00 Jun 01 2010 23:59:59 Sep 12 2010

switch(config-keychain-key) send-lifetime 00:00:00 Jun 01 2010 23:59:59 Aug 12 2010

switch(config-keychain-key) key 1

switch(config-keychain-key) key-string 7 uaeqdyito

switch(config-keychain-key) accept-lifetime 00:00:00 Aug 12 2010 23:59:59 Dec 12 2010

switch(config-keychain-key) send-lifetime 00:00:00 Sep 12 2010 23:59:59 Nov 12 2010

switch(config-keychain-key)# interface ethernet 1/2

switch(config-if)# hsrp 2

switch(config-if-hsrp)# authenticate md5 key-chain hsrp-keys

switch(config-if-hsrp)# copy running-config startup-config

Configuring HSRP Object Tracking

You can configure an HSRP group to adjust its priority based on the availability of other interfaces or routes. The priority of a device can change dynamically if it has been configured for object tracking and the object that is being tracked goes down.

The tracking process periodically polls the tracked objects and notes any value change. The value change triggers HSRP to recalculate the priority. The HSRP interface with the higher priority becomes the active router if you configure the HSRP interface for preemption.

SUMMARY STEPS

1. configure terminal

2. track object-id interface interface-type number {{ip | ipv6} routing | line-protocol}

3. track object-id {ip | ipv6} route ip-prefix/length reachability

4. interface interface-type slot/port

5. hsrp group-number [ipv4 | ipv6]

6. priority [value]

7. track object-number [decrement value]

8. preempt [delay [minimum seconds] [reload seconds] [sync seconds]]

9. (Optional) show hsrp interface interface-type number

10. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

track object-id interface interface-type number {{ip | ipv6} routing | line-protocol}

Example:

switch(config)# track 1 interface ethernet 2/2 line-protocol

switch(config-track#

Configures the interface that this HSRP interface tracks. Changes in the state of the interface affect the priority of this HSRP interface as follows:

- You configure the interface and corresponding object number that you use with the track command in hsrp configuration mode.

- The line-protocol keyword tracks whether the interface is up. The ip keyword also checks that IP routing is enabled on the interface and an IP address is configured.

track object-id {ip | ipv6} route ip-prefix/length reachability

Example:

switch(config)# track 2 ip route 192.0.2.0/8 reachability

switch(config-track#

Creates a tracked object for a route and enters tracking configuration mode. The object-id range is from 1 to 500.

Step 3

interface interface-type slot/port

Example:

switch(config)# interface ethernet 1/2

switch(config-if)#

Enters interface configuration mode.

Step 4

hsrp group-number [ipv4 | ipv6]

Example:

switch(config-if)# hsrp 2

switch(config-if-hsrp)#

Creates an HSRP group and enters hsrp configuration mode.

Step 5

priority [value]

Example:

switch(config-if-hsrp)# priority 254

Sets the priority level used to select the active router in an HSRP group. The range is from 0 to 255. The default is 100.

Step 6

track object-number [decrement value]

Example:

switch(config-if-hsrp)# track 1 decrement 20

Specifies an object to be tracked that affects the weighting of an HSRP interface.

The value argument specifies a reduction in the priority of an HSRP interface when a tracked object fails. The range is from 1 to 255. The default is 10.

Step 7

preempt [delay [minimum seconds] [reload seconds] [sync seconds]]

Example:

switch(config-if-hsrp)# preempt delay minimum 60

Configures the router to take over as the active router for an HSRP group if it has a higher priority than the current active router. This command is disabled by default. The range is from 0 to 3600 seconds.

Step 8

show hsrp interface interface-type number

Example:

switch(config-if-hsrp)# show hsrp interface ethernet 1/2

(Optional) Displays HSRP information for an interface.

Step 9

copy running-config startup-config

Example:

switch(config-if-hsrp)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to configure HSRP object tracking on Ethernet 1/2:

switch# configure terminal

switch(config)# track 1 interface ethernet 2/2 line-protocol

switch(config)# interface ethernet 1/2

switch(config-if)# hsrp 2

switch(config-if-hsrp)# track 1 decrement 20

switch(config-if-hsrp)# copy running-config startup-config

Configuring the HSRP Priority

You can configure the HSRP priority on an interface. HSRP uses the priority to determine which HSRP group member acts as the active router. If you configure HSRP on a vPC-enabled interface, you can optionally configure the upper and lower threshold values to control when to fail over to the vPC trunk If the standby router priority falls below the lower threshold, HSRP sends all standby router traffic across the vPC trunk to forward through the active HSRP router. HSRP maintains this scenario until the standby HSRP router priority increases above the upper threshold.

For IPv6 HSRP groups, if all group members have the same priority, HSRP selects the active router based on the IPv6 link-local address.

Command

Purpose

priority level [forwarding-threshold lower lower-value upper upper-value]

Example:

switch(config-if-hsrp)# priority 60 forwarding-threshold lower 40 upper 50

Sets the priority level used to select the active router in an HSRP group. The level range is from 0 to 255. The default is 100. Optionally, sets the upper and lower threshold values used by vPC to determine when to fail over to the vPC trunk. The lower-value range is from 1 to 255. The default is 1. The upper-value range is from 1 to 255. The default is 255.

Customizing HSRP

You can optionally customize the behavior of HSRP. Be aware that as soon as you enable an HSRP group by configuring a virtual IP address, that group is now operational. If you first enable an HSRP group before customizing HSRP, the router could take control over the group and become the active router before you finish customizing the feature. If you plan to customize HSRP, you should do so before you enable the HSRP group. To customize HSRP, use the following commands in HSRP configuration mode:

Command

Purpose

name string

Example:

switch(config-if-hsrp)# name HSRP-1

Specifies the IP redundancy name for an HSRP group. The string is from 1 to 255 characters. The default string has the following format:

hsrp-interface short-name group-id. For example, hsrp-Eth2/1-1.

preempt [delay [minimum seconds] [reload seconds] [sync seconds]]

Example:

switch(config-if-hsrp)# preempt delay minimum 60

Configures the router to take over as an active router for an HSRP group if it has a higher priority than the current active router. This command is disabled by default. The range is from 0 to 3600 seconds.

timers [msec] hellotime [msec] holdtime

Example:

switch(config-if-hsrp)# timers 5 18

Configures the hello and hold time for this HSRP member as follows:

- hellotime —The interval between successive hello packets sent. The range is from 1 to 254 seconds.

- holdtime —The interval before the information in the hello packet is considered invalid. The range is from 3 to 255.

The optional msec keyword specifies that the argument is expressed in milliseconds instead of the default seconds. The timer ranges for milliseconds are as follows:

- hellotime —The interval between successive hello packets sent. The range is from 255 to 999 milliseconds.

- holdtime —The interval before the information in the hello packet is considered invalid. The range is from 750 to 3000 milliseconds.

Command

Purpose

hsrp delay minimum seconds

Example:

switch(config-if)# hsrp delay minimum 30

Specifies the minimum amount of time that HSRP waits after a group is enabled before participating in the group. The range is from 0 to 10000 seconds. The default is 0.

hsrp delay reload seconds

Example:

switch(config-if)# hsrp delay reload 30

Specifies the minimum amount of time that HSRP waits after reload before participating in the group. The range is from 0 to 10000 seconds. The default is 0.

Configuring Extended Hold Timers for HSRP

You can configure HSRP to use extended hold timers to support extended NSF during a controlled (graceful) switchover or ISSU, including software upgrades and supervisor switchovers.You should configure extended hold timers on all HSRP routers (see the “High Availability and Extended Nonstop Forwarding” section).

Note You must configure extended hold timers on all HSRP routers if you configure extended hold timers. If you configure a nondefault hold timer, you should configure the same value on all HSRP routers when you configure HSRP extended hold timers.

Note HSRP extended hold timers are not applied if you configure millisecond hello and hold timers for HSRPv1. This statement does not apply to HSRPv2.

Command

Purpose

hsrp timers extended-hold [timer]

Example:

switch(config)# hsrp timers extended-hold

Sets the HSRP extended hold timer, in seconds, for both IPv4 and IPv6 groups. The timer range is from 10 to 255. The default is 10.

Use the show hsrp command or the show running-config hsrp command to display the extended hold time.

Verifying the HSRP Configuration

Command

Purpose

show hsrp [group group-number]

Displays the HSRP status for all groups or one group.

show hsrp delay [interface interface-type slot/port]

Displays the HSRP delay value for all interfaces or one interface.

show hsrp [interface interface-type slot/port]

Displays the HSRP status for an interface.

show hsrp [group group-number] [interface interface-type slot/port] [active] [all] [init] [learn] [listen] [speak] [standby]

Displays the HSRP status for a group or interface for virtual forwarders in the active, init, learn, listen, or standby state. Use the all keyword to see all states, including disabled.

show hsrp [group group-number] [interface interface-type slot/port] active] [all] [init] [learn] [listen] [speak] [standby] brief

Displays a brief summary of the HSRP status for a group or interface for virtual forwarders in the active, init, learn, listen, or standby state. Use the all keyword to see all states, including disabled.

Configuration Examples for HSRP

This example shows how to enable HSRP on an interface with MD5 authentication and interface tracking:

key chain hsrp-keys

key 0

key-string 7 zqdest

accept-lifetime 00:00:00 Jun 01 2008 23:59:59 Sep 12 2008

send-lifetime 00:00:00 Jun 01 2008 23:59:59 Aug 12 2008

key 1

key-string 7 uaeqdyito

accept-lifetime 00:00:00 Aug 12 2008 23:59:59 Dec 12 2008

send-lifetime 00:00:00 Sep 12 2008 23:59:59 Nov 12 2008

feature hsrp

track 2 interface ethernet 2/2 ip

interface ethernet 1/2

ip address 192.0.2.2/8

hsrp 1

authenticate md5 key-chain hsrp-keys

priority 90

track 2 decrement 20

ip 192.0.2.10

no shutdown

This example shows how to configure the HSRP priority on an interface:

interface vlan 1

hsrp 0

preempt

priority 100 forwarding-threshold lower 80 upper 90

ip 192.0.2.2

track 1 decrement 30

Additional References

For additional information related to implementing HSRP, see the following sections:

- Related Documents

- MIBs

Related Documents

Related Topic

Document Title

Configuring the Gateway Load Balancing protocol

Chapter 18, “Configuring GLBP”

Configuring the Virtual Router Redundancy protocol

Chapter 20, “Configuring VRRP”

HSRP CLI commands

Cisco Nexus 7000 Series NX-OS Unicast Routing Command Reference, Release 5.x

Configuring high availability

Cisco Nexus 7000 Series NX-OS High Availability and Redundancy Guide, Release 5.x

MIBs

MIBs

MIBs Link

CISCO-HSRP-MIB

To locate and download MIBs, go to the following URL:

http://www.cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml

Feature History for HSRP

Table 19-3 Feature History for HSRP

Feature Name

Releases

Feature Information

BFD

5.0(2)

Added support for BFD. See the Cisco Nexus 7000 Series NX-OS Interfaces Configuration Guide, Release 5.x, for more information.

IPv6

5.0(2)

Added support for IPv6.

Object track lists

4.2(1)

Added support for object track lists.

Extended hold timers

4.2(1)

Added support for extended hold timers for extended NSF support.

CISCO-HSRP-MIB

4.2(1)

Added support for CISCO-HSRP-MIB.

Priority thresholds

4.1(3)

Added support for vPC threshold values on HSRP priority.

HSRP

4.0(1)

This feature was introduced.

Configuring DNS

This chapter describes how to configure the Domain Name Server (DNS) client on the Cisco NX-OS device.

This chapter includes the following sections:

- Information About DNS Clients

- Licensing Requirements for DNS Clients

- Prerequisites for DNS Clients

- Guidelines and Limitations for DNS

- Default Settings

- Configuring DNS Clients

- Verifying the DNS Client Configuration

- Configuration Examples for the DNS Client

- Additional References

- Feature History for DNS

Information About DNS Clients

This section includes the following topics:

- DNS Client Overview

- High Availability

- Virtualization Support

DNS Client Overview

If your network devices require connectivity with devices in networks for which you do not control the name assignment, you can assign device names that uniquely identify your devices within the entire internetwork using the domain name server (DNS). DNS uses a hierarchical scheme for establishing host names for network nodes, which allows local control of the segments of the network through a client-server scheme. The DNS system can locate a network device by translating the hostname of the device into its associated IP address.

On the Internet, a domain is a portion of the naming hierarchy tree that refers to general groupings of networks based on the organization type or geography. Domain names are pieced together with periods (.) as the delimiting characters. For example, Cisco is a commercial organization that the Internet identifies by a com domain, so its domain name is cisco.com. A specific hostname in this domain, the File Transfer Protocol (FTP) system, for example, is identified as ftp.cisco.com.

Name Servers

Name servers keep track of domain names and know the parts of the domain tree for which they have complete information. A name server may also store information about other parts of the domain tree. To map domain names to IP addresses in Cisco NX-OS, you must identify the hostnames, specify a name server, and enable the DNS service.

Cisco NX-OS allows you to statically map IP addresses to domain names. You can also configure Cisco NX-OS to use one or more domain name servers to find an IP address for a host name.

DNS Operation

A name server handles client-issued queries to the DNS server for locally defined hosts within a particular zone as follows:

- An authoritative name server responds to DNS user queries for a domain name that is under its zone of authority by using the permanent and cached entries in its own host table. If the query is for a domain name that is under its zone of authority but for which it does not have any configuration information, the authoritative name server replies that no such information exists.

- A name server that is not configured as the authoritative name server responds to DNS user queries by using information that it has cached from previously received query responses. If no router is configured as the authoritative name server for a zone, queries to the DNS server for locally defined hosts receive nonauthoritative responses.

Name servers answer DNS queries (forward incoming DNS queries or resolve internally generated DNS queries) according to the forwarding and lookup parameters configured for the specific domain.

High Availability

Cisco NX-OS supports stateless restarts for the DNS client. After a reboot or supervisor switchover, Cisco NX-OS applies the running configuration.

Virtualization Support

Cisco NX-OS supports multiple instances of the DNS clients that run on the same system. You can configure a DNS client in each virtual device connect (VDC).You can optionally have a different DNS client configuration in each virtual routing and forwarding (VRF) instance within a VDC. By default, Cisco NX-OS places you in the default VDC and default VRF unless you specifically configure another VDC and VRF. See the Cisco NX-OS Virtual Device Context Configuration Guide and Chapter14, “Configuring Layer 3 Virtualization”

Licensing Requirements for DNS Clients

The following table shows the licensing requirements for this feature:

Product

License Requirement

Cisco NX-OS

DNS requires no license. Any feature not included in a license package is bundled with the Cisco NX-OS system images and is provided at no extra charge to you. For a complete explanation of the Cisco NX-OS licensing scheme, see the Cisco NX-OS Licensing Guide.

Prerequisites for DNS Clients

The DNS client has the following prerequisites:

- You must have a DNS name server on your network.

- If you configure VDCs, install the Advanced Services license and enter the desired VDC (see the Cisco NX-OS Virtual Device Context Configuration Guide).

Guidelines and Limitations for DNS

The DNS client has the following configuration guidelines and limitations:

- You configure the DNS client in a specific VRF. If you do not specify a VRF, Cisco NX-OS uses the default VRF.

Default Settings

Table 4-1 lists the default settings for DNS client parameters.

Table 4-1 Default DNS Client Parameters

Parameters

Default

DNS client

Enabled

Configuring DNS Clients

This section includes the following topics:

- Configuring the DNS Client

- Configuring Virtualization

Note If you are familiar with the Cisco IOS CLI, be aware that the Cisco NX-OS commands for this feature might differ from the Cisco IOS commands that you would use.

Configuring the DNS Client

You can configure the DNS client to use a DNS server on your network.

BEFORE YOU BEGIN

Ensure that you have a domain name server on your network.

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. ip host name address1 [address2... address6]

3. (Optional) ip domain-name name [use-vrf vrf-name]

4. (Optional) ip domain-list name [use-vrf vrf-name]

5. (Optional) ip name-server address1 [address2... address6] [use-vrf vrf-name]

6. (Optional) ip domain lookup

7. (Optional) show hosts

8. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

ip host name address1 [address2... address6]

Example:

switch(config)# ip host cisco-rtp 192.0.2.1

Defines up to six static hostname-to-address mappings in the hostname cache. The address can be either an IPv4 address or an IPv6 address.

Step 3

ip domain-name name [use-vrf vrf-name]

Example:

switch(config)# ip domain-name myserver.com

(Optional) Defines the default domain name that Cisco NX-OS uses to complete unqualified host names. You can optionally define a VRF that Cisco NX-OS uses to resolve this domain name if it cannot be resolved in the VRF that you configured this domain name under.

Cisco NX-OS appends the default domain name to any hostname that does not contain a complete domain name before starting a domain-name lookup.

Step 4

ip domain-list name [use-vrf vrf-name]

Example:

switch(config)# ip domain-list mycompany.com

(Optional) Defines additional domain names that Cisco NX-OS can use to complete unqualified hostnames. You can optionally define a VRF that Cisco NX-OS uses to resolve these domain names if they cannot be resolved in the VRF that you configured this domain name under.

Cisco NX-OS uses each entry in the domain list to append that domain name to any hostname that does not contain a complete domain name before starting a domain-name lookup. Cisco NX-OS continues this process for each entry in the domain list until it finds a match.

Step 5

ip name-server address1 [address2... address6] [use-vrf vrf-name]

Example:

switch(config)# ip name-server 192.0.2.22

(Optional) Defines up to six name servers. The address can be either an IPv4 address or an IPv6 address.

You can optionally define a VRF that Cisco NX-OS uses to reach this name server if it cannot be reached in the VRF that you configured this name server under.

Step 6

ip domain-lookup

Example:

switch(config)# ip domain-lookup

(Optional) Enables DNS-based address translation. This feature is enabled by default.

Step 7

show hosts

Example:

switch(config)# show hosts

(Optional) Displays information about DNS.

Step 8

copy running-config startup-config

Example:

switch(config)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to configure a default domain name and enable DNS lookup:

switch# configure terminal

switch(config)# ip domain-name cisco.com 192.0.2.1 use-vrf management

switch(config)# ip domain-lookup

switch(config)# copy running-config startup-config

Configuring Virtualization

You can configure a DNS client within a VRF. If you do not enter VRF configuration mode, your DNS client configuration applies to the default VRF.

You can optionally configure a DNS client to use a specified VRF other than the VRF under which you configured the DNS client as a backup VRF. For example, you can configure a DNS client in the Red VRF but use the Blue VRF to communicate with the DNS server if the server cannot be reached through the Red VRF.

BEFORE YOU BEGIN

Ensure that you have a domain name server on your network.

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. vrf context vrf-name

3. (Optional) ip domain-name name [use-vrf vrf-name]

4. (Optional) ip domain-list name [use-vrf vrf-name]

5. (Optional) ip name-server server-address1 [server-address2... server-address6] [use-vrf vrf-name]

6. (Optional) show hosts

7. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

vrf context vrf-name

Example:

switch(config)# vrf context Red

switch(config-vrf)#

Creates a VRF and enters VRF configuration mode.

Step 3

ip domain-name name [use-vrf vrf-name]

Example:

switch(config-vrf)# ip domain-name myserver.com

(Optional) Defines the default domain name server that Cisco NX-OS uses to complete unqualified hostnames. You can optionally define a VRF that Cisco NX-OS uses to resolve this domain name server if it cannot be resolved in the VRF under which you configured this domain name.

Cisco NX-OS appends the default domain name to any hostname that does not contain a complete domain name before starting a domain-name lookup.

Step 4

ip domain-list name [use-vrf vrf-name]

Example:

switch(config-vrf)# ip domain-list mycompany.com

(Optional) Defines additional domain name servers that Cisco NX-OS can use to complete unqualified hostnames. You can optionally define a VRF that Cisco NX-OS uses to resolve this domain name server if it cannot be resolved in the VRF under which you configured this domain name.

Cisco NX-OS uses each entry in the domain list to append that domain name to any hostname that does not contain a complete domain name before starting a domain-name lookup. Cisco NX-OS continues this process for each entry in the domain list until it finds a match.

Step 5

ip name-server address1 [address2... address6] [use-vrf vrf-name]

Example:

switch(config-vrf)# ip name-server 192.0.2.22

(Optional) Defines up to six name servers. The address can be either an IPv4 address or an IPv6 address.

You can optionally define a VRF that Cisco NX-OS uses to reach this name server if it cannot be reached in the VRF that you configured this name server under.

Step 6

show hosts

Example:

switch(config-vrf)# show hosts

(Optional) Displays information about DNS.

Step 7

copy running-config startup-config

Example:

switch(config-vrf)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to configure a default domain name and enable DNS lookup within a VRF:

switch# configure terminal

switch(config)# vrf context Red

switch(config-vrf)# ip domain-name cisco.com 192.0.2.1 use-vrf management

switch(config-vrf)# copy running-config startup-config

Verifying the DNS Client Configuration

To display the DNS client configuration, perform one of the following tasks:

Command

Purpose

show hosts

Displays information about DNS.

Configuration Examples for the DNS Client

This example shows how to establish a domain list with several alternate domain names:

ip domain list csi.com

ip domain list telecomprog.edu

ip domain list merit.edu

This example shows how to configure the hostname-to-address mapping process and specify IP DNS-based translation. The example also configures the addresses of the name servers and the default domain name.

ip domain lookup

ip name-server 192.168.1.111 192.168.1.2

ip domain name cisco.com

Additional References

For additional information related to implementing DNS Client, see the following sections:

- Related Documents

- Standards

Related Documents

Related Topic

Document Title

DNS Client CLI commands

Cisco Nexus 7000 Series NX-OS Unicast Routing Command Reference, Release 5.x

VDCs and VRFs

Cisco Nexus 7000 Series NX-OS Virtual Device Context Configuration Guide, Release 5.x

Standards

Standards

Title

No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.

—

Feature History for DNS

Table 4-2 lists the release history for this feature.

Table 4-2 Feature History for DNS

Feature Name

Releases

Feature Information

DNS

4.0(1)

This feature was introduced.

Configuring IPv6

This chapter describes how to configure Internet Protocol version 6 (IPv6), which includes addressing, Neighbor Discovery Protocol (ND), and Internet Control Message Protocol version 6 (ICMPv6), on the Cisco NX-OS device.

This chapter includes the following sections:

- Information About IPv6

- Licensing Requirements for IPv6

- Prerequisites for IPv6

- Guidelines and Limitations for IPv6

- Default Settings

- Configuring IPv6

- Verifying the IPv6 Configuration

- Configuration Examples for IPv6

- Additional References

- Feature History for IPv6

Information About IPv6

IPv6, which is designed to replace IPv4, increases the number of network address bits from 32 bits (in IPv4) to 128 bits. IPv6 is based on IPv4 but it includes a much larger address space and other improvements such as a simplified main header and extension headers.

The larger IPv6 address space allows networks to scale and provide global reachability. The simplified IPv6 packet header format handles packets more efficiently. The flexibility of the IPv6 address space reduces the need for private addresses and the use of Network Address Translation (NAT), which translates private (not globally unique) addresses into a limited number of public addresses. IPv6 enables new application protocols that do not require special processing by border routers at the edge of networks.

IPv6 functionality, such as prefix aggregation, simplified network renumbering, and IPv6 site multihoming capabilities, enable more efficient routing. IPv6 supports Routing Information Protocol (RIP), Integrated Intermediate System-to-Intermediate System (IS-IS), Open Shortest Path First (OSPF) for IPv6, and multiprotocol Border Gateway Protocol (BGP).

This section includes the following topics:

- IPv6 Address Formats

- IPv6 Unicast Addresses

- IPv6 Anycast Addresses

- IPv6 Multicast Addresses

- IPv4 Packet Header

- Simplified IPv6 Packet Header

- DNS for IPv6

- Path MTU Discovery for IPv6

- CDP IPv6 Address Support

- ICMP for IPv6

- IPv6 Neighbor Discovery

- IPv6 Neighbor Solicitation Message

- IPv6 Router Advertisement Message

- IPv6 Neighbor Redirect Message

- Virtualization Support

IPv6 Address Formats

Note You can use two colons (::) only once in an IPv6 address to replace the longest string of consecutive zeros within the address.

You can use a double colon as part of the IPv6 address when consecutive 16-bit values are denoted as zero. You can configure multiple IPv6 addresses per interface but only one link-local address.

The hexadecimal letters in IPv6 addresses are not case sensitive.

Table 3-1 Compressed IPv6 Address Formats

IPv6 Address Type

Preferred Format

Compressed Format

Unicast

2001:0:0:0:0DB8:800:200C:417A

2001::0DB8:800:200C:417A

Multicast

FF01:0:0:0:0:0:0:101

FF01::101

Loopback

0:0:0:0:0:0:0:0:1

::1

Unspecified

0:0:0:0:0:0:0:0:0

::

A node may use the loopback address listed in Table 3-1 to send an IPv6 packet to itself. The loopback address in IPv6 is the same as the loopback address in IPv4. For more information, see Chapter1, “Overview”

Note You cannot assign the IPv6 loopback address to a physical interface. A packet that contains the IPv6 loopback address as its source or destination address must remain within the node that created the packet. IPv6 routers do not forward packets that have the IPv6 loopback address as their source or destination address.

Note You cannot assign an IPv6 unspecified address to an interface. You should not use the unspecified IPv6 addresses as destination addresses in IPv6 packets or the IPv6 routing header.

The IPv6-prefix is in the form documented in RFC 2373 where the IPv6 address is specified in hexadecimal using 16-bit values between colons. The prefix length is a decimal value that indicates how many of the high-order contiguous bits of the address comprise the prefix (the network portion of the address). For example, 2001:0DB8:8086:6502::/32 is a valid IPv6 prefix.

IPv6 Unicast Addresses

An IPv6 unicast address is an identifier for a single interface on a single node. A packet that is sent to a unicast address is delivered to the interface identified by that address. This section includes the following topics:

- Aggregatable Global Addresses

- Link-Local Addresses

- IPv4-Compatible IPv6 Addresses

- Unique Local Addresses

- Site-Local Address

Aggregatable Global Addresses

An aggregatable global address is an IPv6 address from the aggregatable global unicast prefix. The structure of aggregatable global unicast addresses enables strict aggregation of routing prefixes that limits the number of routing table entries in the global routing table. Aggregatable global addresses are used on links that are aggregated upward through organizations and eventually to the Internet service providers (ISPs).

Aggregatable global IPv6 addresses are defined by a global routing prefix, a subnet ID, and an interface ID. Except for addresses that start with binary 000, all global unicast addresses have a 64-bit interface ID. The IPv6 global unicast address allocation uses the range of addresses that start with binary value 001 (2000::/3). Figure 3-1 shows the structure of an aggregatable global address.

Figure 3-1 Aggregatable Global Address Format

Addresses with a prefix of 2000::/3 (001) through E000::/3 (111) are required to have 64-bit interface identifiers in the extended universal identifier (EUI)-64 format. The Internet Assigned Numbers Authority (IANA) allocates the IPv6 address space in the range of 2000::/16 to regional registries.

The aggregatable global address consists of a 48-bit global routing prefix and a 16-bit subnet ID or Site-Level Aggregator (SLA). In the IPv6 aggregatable global unicast address format document (RFC 2374), the global routing prefix included two other hierarchically structured fields called Top-Level Aggregator (TLA) and Next-Level Aggregator (NLA). The IETF decided to remove the TLS and NLA fields from the RFCs because these fields are policy based. Some existing IPv6 networks deployed before the change might still use networks that are on the older architecture.

A subnet ID, which is a 16-bit subnet field, can be used by individual organizations to create a local addressing hierarchy and to identify subnets. A subnet ID is similar to a subnet in IPv4, except that an organization with an IPv6 subnet ID can support up to 65,535 individual subnets.

An interface ID identifies interfaces on a link. The interface ID is unique to the link. In many cases, an interface ID is the same as or based on the link-layer address of an interface. Interface IDs used in aggregatable global unicast and other IPv6 address types have 64 bits and are in the modified EUI-64 format.

Interface IDs are in the modified EUI-64 format in one of the following ways:

- For all IEEE 802 interface types (for example, Ethernet, and Fiber Distributed Data interfaces), the first three octets (24 bits) are the Organizationally Unique Identifier (OUI) of the 48-bit link-layer address (MAC address) of the interface, the fourth and fifth octets (16 bits) are a fixed hexadecimal value of FFFE, and the last three octets (24 bits) are the last three octets of the MAC address. The Universal/Local (U/L) bit, which is the seventh bit of the first octet, has a value of 0 or 1. Zero indicates a locally administered identifier; 1 indicates a globally unique IPv6 interface identifier.

- For all other interface types (for example, serial, loopback, ATM, Frame Relay, and tunnel interface types—except tunnel interfaces used with IPv6 overlay tunnels), the interface ID is similar to the interface ID for IEEE 802 interface types; however, the first MAC address from the pool of MAC addresses in the router is used as the identifier (because the interface does not have a MAC address).

- For tunnel interface types that are used with IPv6 overlay tunnels, the interface ID is the IPv4 address assigned to the tunnel interface with all zeros in the high-order 32 bits of the identifier.

Note For interfaces that use the Point-to-Point Protocol (PPP), where the interfaces at both ends of the connection might have the same MAC address, the interface identifiers at both ends of the connection are negotiated (picked randomly and, if necessary, reconstructed) until both identifiers are unique. The first MAC address in the router is used as the identifier for interfaces using PPP.

If no IEEE 802 interface types are in the router, link-local IPv6 addresses are generated on the interfaces in the router in the following sequence:

1. The router is queried for MAC addresses (from the pool of MAC addresses in the router).

2. If no MAC addresses are available in the router, the serial number of the router is used to form the link-local addresses.

3. If the serial number of the router cannot be used to form the link-local addresses, the router uses a Message Digest 5 (MD5) hash to determine the MAC address of the router from the hostname of the router.

Link-Local Addresses

A link-local address is an IPv6 unicast address that can be automatically configured on any interface using the link-local prefix FE80::/10 (1111 1110 10) and the interface identifier in the modified EUI-64 format. Link-local addresses are used in the Neighbor Discovery Protocol (NDP) and the stateless autoconfiguration process. Nodes on a local link can use link-local addresses to communicate; the nodes do not need globally unique addresses to communicate. Figure 3-2 shows the structure of a link-local address.

IPv6 routers cannot forward packets that have link-local source or destination addresses to other links.

Figure 3-2 Link-Local Address Format

IPv4-Compatible IPv6 Addresses

An IPv4-compatible IPv6 address is an IPv6 unicast address that has zeros in the high-order 96 bits of the address and an IPv4 address in the low-order 32 bits of the address. The format of an IPv4-compatible IPv6 address is 0:0:0:0:0:0:A.B.C.D or ::A.B.C.D. The entire 128-bit IPv4-compatible IPv6 address is used as the IPv6 address of a node and the IPv4 address embedded in the low-order 32 bits is used as the IPv4 address of the node. IPv4-compatible IPv6 addresses are assigned to nodes that support both the IPv4 and IPv6 protocol stacks and are used in automatic tunnels. Figure 3-3 shows the structure of an IPv4-compatible IPv6 address and a few acceptable formats for the address.

Figure 3-3 IPv4-Compatible IPv6 Address Format

Unique Local Addresses

A unique local address is an IPv6 unicast address that is globally unique and is intended for local communications. It is not expected to be routable on the global Internet and is routable inside of a limited area, such as a site, and it may be routed between a limited set of sites. Applications may treat unique local addresses like global scoped addresses.

A unique local address has the following characteristics:

- It has a globally unique prefix (it has a high probability of uniqueness).

- It has a well-known prefix to allow for easy filtering at site boundaries.

- It allows sites to be combined or privately interconnected without creating any address conflicts or requiring renumbering of interfaces that use these prefixes.

- It is ISP-independent and can be used for communications inside of a site without having any permanent or intermittent Internet connectivity.

- If it is accidentally leaked outside of a site through routing or the Domain Name Server (DNS), there is no conflict with any other addresses.

Figure 3-4 shows the structure of a unique local address.

Figure 3-4 Unique Local Address Structure

Site-Local Address

Because RFC 3879 deprecates the use of site-local addresses, you should follow the recommendations of unique local addressing (ULA) in RFC 4193 when you configure private IPv6 addresses.

IPv6 Anycast Addresses

An anycast address is an address that is assigned to a set of interfaces that belong to different nodes. A packet sent to an anycast address is delivered to the closest interface—as defined by the routing protocols in use—identified by the anycast address. Anycast addresses are syntactically indistinguishable from unicast addresses because anycast addresses are allocated from the unicast address space. Assigning a unicast address to more than one interface turns a unicast address into an anycast address. You must configure the nodes to which the anycast address to recognize that the address is an anycast address.

Note Anycast addresses can be used only by a router, not a host. Anycast addresses cannot be used as the source address of an IPv6 packet.

Figure 3-5 shows the format of the subnet router anycast address; the address has a prefix concatenated by a series of zeros (the interface ID). The subnet router anycast address can be used to reach a router on the link that is identified by the prefix in the subnet router anycast address.

Figure 3-5 Subnet Router Anycast Address Format

IPv6 Multicast Addresses

An IPv6 multicast address is an IPv6 address that has a prefix of FF00::/8 (1111 1111). An IPv6 multicast address is an identifier for a set of interfaces that belong to different nodes. A packet sent to a multicast address is delivered to all interfaces identified by the multicast address. The second octet following the prefix defines the lifetime and scope of the multicast address. A permanent multicast address has a lifetime parameter equal to 0; a temporary multicast address has a lifetime parameter equal to 1. A multicast address that has the scope of a node, link, site, or organization, or a global scope, has a scope parameter of 1, 2, 5, 8, or E, respectively. For example, a multicast address with the prefix FF02::/16 is a permanent multicast address with a link scope. Figure 3-6 shows the format of the IPv6 multicast address.

Figure 3-6 IPv6 Multicast Address Format

IPv6 nodes (hosts and routers) are required to join (where received packets are destined for) the following multicast groups:

- All-nodes multicast group FF02:0:0:0:0:0:0:1 (the scope is link-local)

- Solicited-node multicast group FF02:0:0:0:0:1:FF00:0000/104 for each of its assigned unicast and anycast addresses

IPv6 routers must also join the all-routers multicast group FF02:0:0:0:0:0:0:2 (the scope is link-local).

The solicited-node multicast address is a multicast group that corresponds to an IPv6 unicast or anycast address. IPv6 nodes must join the associated solicited-node multicast group for every unicast and anycast address to which it is assigned. The IPv6 solicited-node multicast address has the prefix FF02:0:0:0:0:1:FF00:0000/104 concatenated with the 24 low-order bits of a corresponding IPv6 unicast or anycast address (see Figure 3-7). For example, the solicited-node multicast address that corresponds to the IPv6 address 2037::01:800:200E:8C6C is FF02::1:FF0E:8C6C. Solicited-node addresses are used in neighbor solicitation messages.

Figure 3-7 IPv6 Solicited-Node Multicast Address Format

Note IPv6 has no broadcast addresses. IPv6 multicast addresses are used instead of broadcast addresses.

IPv4 Packet Header

The base IPv4 packet header has 12 fields with a total size of 20 octets (160 bits) (see Figure 3-8). The 12 fields may be followed by an Options field, which is followed by a data portion that is usually the transport-layer packet. The variable length of the Options field adds to the total size of the IPv4 packet header. The shaded fields of the IPv4 packet header are not included in the IPv6 packet header.

Figure 3-8 IPv4 Packet Header Format

Simplified IPv6 Packet Header

The base IPv6 packet header has 8 fields with a total size of 40 octets (320 bits) (see Figure 3-9). Fragmentation is handled by the source of a packet and checksums at the data link layer and transport layer are used. The User Datagram Protocol (UDP) checksum checks the integrity of the inner packet and the base IPv6 packet header and Options field are aligned to 64 bits, which can facilitate the processing of IPv6 packets.

Table 3-2 lists the fields in the base IPv6 packet header.

Table 3-2 Base IPv6 Packet Header Fields

Field

Description

Version

Similar to the Version field in the IPv4 packet header, except that the field lists number 6 for IPv6 instead of number 4 for IPv4.

Traffic Class

Similar to the Type of Service field in the IPv4 packet header. The Traffic Class field tags packets with a traffic class that is used in differentiated services.

Flow Label

New field in the IPv6 packet header. The Flow Label field tags packets with a specific flow that differentiates the packets at the network layer.

Payload Length

Similar to the Total Length field in the IPv4 packet header. The Payload Length field indicates the total length of the data portion of the packet.

Next Header

Similar to the Protocol field in the IPv4 packet header. The value of the Next Header field determines the type of information that follows the base IPv6 header. The type of information that follows the base IPv6 header can be a transport-layer packet, for example, a TCP or UDP packet, or an Extension Header, as shown in Figure 3-9.

Hop Limit

Similar to the Time to Live field in the IPv4 packet header. The value of the Hop Limit field specifies the maximum number of routers that an IPv6 packet can pass through before the packet is considered invalid. Each router decrements the value by one. Because no checksum is in the IPv6 header, the router can decrement the value without needing to recalculate the checksum, which saves processing resources.

Source Address

Similar to the Source Address field in the IPv4 packet header, except that the field contains a 128-bit source address for IPv6 instead of a 32-bit source address for IPv4.

Destination Address

Similar to the Destination Address field in the IPv4 packet header, except that the field contains a 128-bit destination address for IPv6 instead of a 32-bit destination address for IPv4.

Figure 3-9 IPv6 Packet Header Format

Optional extension headers and the data portion of the packet are after the eight fields of the base IPv6 packet header. If present, each extension header is aligned to 64 bits. There is no fixed number of extension headers in an IPv6 packet. Each extension header is identified by the Next Header field of the previous header. Typically, the final extension header has a Next Header field of a transport-layer protocol, such as TCP or UDP. Figure 3-10 shows the IPv6 extension header format.

Figure 3-10 IPv6 Extension Header Format

Table 3-3 IPv6 Extension Header Types

Header Type

Next Header Value

Description

Hop-by-hop options header

0

Header that is processed by all hops in the path of a packet. When present, the hop-by-hop options header always follows immediately after the base IPv6 packet header.

Destination options header

60

Header that can follow any hop-by-hop options header. The header is processed at the final destination and at each visited address specified by a routing header. Alternatively, the destination options header can follow any Encapsulating Security Payload (ESP) header. The destination options header is processed only at the final destination.

Routing header

43

Header that is used for source routing.

Fragment header

44

Header that is used when a source fragments a packet that is larger than the maximum transmission unit (MTU) for the path between itself and a destination. The Fragment header is used in each fragmented packet.

Upper-layer headers

6 (TCP)

17 (UDP)

Headers that are used inside a packet to transport the data. The two main transport protocols are TCP and UDP.

DNS for IPv6

IPv6 supports DNS record types that are supported in the DNS name-to-address and address-to-name lookup processes. The DNS record types support IPv6 addresses (see Table 3-4).

Note IPv6 also supports the reverse mapping of IPv6 addresses to DNS names.

Table 3-4 IPv6 DNS Record Types

Record Type

Description

Format

AAAA

Maps a hostname to an IPv6 address. (Equivalent to an A record in IPv4.)

www.abc.test AAAA 3FFE:YYYY:C18:1::2

PTR

Maps an IPv6 address to a hostname. (Equivalent to a PTR record in IPv4.)

2.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.1.0.0.0.8.1.c.0.y.y.y.y.e.f.f.3.ip6.int PTR www.abc.test

Path MTU Discovery for IPv6

As in IPv4, you can use path MTU discovery in IPv6 to allow a host to dynamically discover and adjust to differences in the MTU size of every link along a data path. In IPv6, however, fragmentation is handled by the source of a packet when the path MTU of one link along a given data path is not large enough to accommodate the size of the packets. Having IPv6 hosts handle packet fragmentation saves IPv6 router processing resources and helps IPv6 networks run more efficiently. Once the path MTU is reduced by the arrival of an ICMP Too Big message, Cisco NX-OS retains the lower value. The connection does not increase the segment size to gauge the throughput.

Note In IPv6, the minimum link MTU is 1280 octets. We recommend that you use an MTU value of 1500 octets for IPv6 links.

CDP IPv6 Address Support

You can use the Cisco Discovery Protocol (CDP) IPv6 address support for the neighbor information feature to transfer IPv6 addressing information between two Cisco devices. Cisco Discovery Protocol support for IPv6 addresses provides IPv6 information to network management products and troubleshooting tools.

ICMP for IPv6

You can use ICMP in IPv6 to provide information about the health of the network. ICMPv6, the version that works with IPv6, reports errors if packets cannot be processed correctly and sends informational messages about the status of the network. For example, if a router cannot forward a packet because it is too large to be sent out on another network, the router sends out an ICMPv6 message to the originating host. Additionally, ICMP packets in IPv6 are used in IPv6 neighbor discovery and path MTU discovery. The path MTU discovery process ensures that a packet is sent using the largest possible size that is supported on a specific route.

A value of 58 in the Next Header field of the base IPv6 packet header identifies an IPv6 ICMP packet. The ICMP packet follows all the extension headers and is the last piece of information in the IPv6 packet.Within the IPv6 ICMP packets, the ICMPv6 Type and ICMPv6 Code fields identify IPv6 ICMP packet specifics, such as the ICMP message type. The value in the Checksum field is computed by the sender and checked by the receiver from the fields in the IPv6 ICMP packet and the IPv6 pseudo header.

Note The IPv6 header does not have a checksum. But a checksum on the transport layer can determine if packets have not been delivered correctly. All checksum calculations that include the IP address in the calculation must be modified for IPv6 to accommodate the new 128-bit address. A checksum is generated using a pseudo header.

The ICMPv6 Payload field contains error or diagnostic information that relates to IP packet processing. Figure 3-11 shows the IPv6 ICMP packet header format.

Figure 3-11 IPv6 ICMP Packet Header Format

IPv6 Neighbor Discovery

You can use the IPv6 Neighbor Discovery Protocol (NDP) to determine whether a neighboring router is reachable. IPv6 nodes use neighbor discovery to determine the addresses of nodes on the same network (local link), to find neighboring routers that can forward their packets, to verify whether neighboring routers are reachable or not, and to detect changes to link-layer addresses. NDP uses ICMP messages to detect whether packets are sent to neighboring routers that are unreachable.

IPv6 Neighbor Solicitation Message

A node sends a neighbor solicitation message, which has a value of 135 in the Type field of the ICMP packet header, on the local link when it wants to determine the link-layer address of another node on the same local link (see Figure 3-12). The source address is the IPv6 address of the node that sends the neighbor solicitation message. The destination address is the solicited-node multicast address that corresponds to the IPv6 address of the destination node. The neighbor solicitation message also includes the link-layer address of the source node.

Figure 3-12 IPv6 Neighbor Discovery—Neighbor Solicitation Message

After receiving the neighbor solicitation message, the destination node replies by sending a neighbor advertisement message, which has a value of 136 in the Type field of the ICMP packet header, on the local link. The source address is the IPv6 address of the node (the IPv6 address of the node interface that sends the neighbor advertisement message). The destination address is the IPv6 address of the node that sends the neighbor solicitation message. The data portion includes the link-layer address of the node that sends the neighbor advertisement message.

After the source node receives the neighbor advertisement, the source node and destination node can communicate.

Neighbor solicitation messages can verify the reachability of a neighbor after a node identifies the link-layer address of a neighbor. When a node wants to verify the reachability of a neighbor, it uses the destination address in a neighbor solicitation message as the unicast address of the neighbor.

Neighbor advertisement messages are also sent when there is a change in the link-layer address of a node on a local link. When there is a change, the destination address for the neighbor advertisement is the all-nodes multicast address.

Neighbor unreachability detection identifies the failure of a neighbor or the failure of the forward path to the neighbor and is used for all paths between hosts and neighboring nodes (hosts or routers). Neighbor unreachability detection is performed for neighbors to which only unicast packets are being sent and is not performed for neighbors to which multicast packets are being sent.

A neighbor is considered reachable when a positive acknowledgment is returned from the neighbor (indicating that packets previously sent to the neighbor have been received and processed). A positive acknowledgment—from an upper-layer protocol (such as TCP)—indicates that a connection is making forward progress (reaching its destination). If packets are reaching the peer, they are also reaching the next-hop neighbor of the source. Forward progress is also a confirmation that the next-hop neighbor is reachable.

For destinations that are not on the local link, forward progress implies that the first-hop router is reachable. When acknowledgments from an upper-layer protocol are not available, a node probes the neighbor using unicast neighbor solicitation messages to verify that the forward path is still working. The return of a solicited neighbor advertisement message from the neighbor is a positive acknowledgment that the forward path is still working (neighbor advertisement messages that have the solicited flag set to a value of 1 are sent only in response to a neighbor solicitation message). Unsolicited messages confirm only the one-way path from the source to the destination node; solicited neighbor advertisement messages indicate that a path is working in both directions.

Note A neighbor advertisement message that has the solicited flag set to a value of 0 is not considered as a positive acknowledgment that the forward path is still working.

Neighbor solicitation messages are also used in the stateless autoconfiguration process to verify the uniqueness of unicast IPv6 addresses before the addresses are assigned to an interface. Duplicate address detection is performed first on a new, link-local IPv6 address before the address is assigned to an interface (the new address remains in a tentative state while duplicate address detection is performed). A node sends a neighbor solicitation message with an unspecified source address and a tentative link-local address in the body of the message. If another node is already using that address, the node returns a neighbor advertisement message that contains the tentative link-local address. If another node is simultaneously verifying the uniqueness of the same address, that node also returns a neighbor solicitation message. If no neighbor advertisement messages are received in response to the neighbor solicitation message and no neighbor solicitation messages are received from other nodes that are attempting to verify the same tentative address, the node that sent the original neighbor solicitation message considers the tentative link-local address to be unique and assigns the address to the interface.

IPv6 Router Advertisement Message

Router advertisement (RA) messages, which have a value of 134 in the Type field of the ICMP packet header, are periodically sent out to each configured interface of an IPv6 router. For stateless autoconfiguration to work properly, the advertised prefix length in RA messages must always be 64 bits.

The RA messages are sent to the all-nodes multicast address (see Figure 3-13).

Figure 3-13 IPv6 Neighbor Discovery—RA Message

RA messages typically include the following information:

- One or more onlink IPv6 prefixes that nodes on the local link can use to automatically configure their IPv6 addresses

- Life-time information for each prefix included in the advertisement

- Sets of flags that indicate the type of autoconfiguration (stateless or stateful) that can be completed

- Default router information (whether the router sending the advertisement should be used as a default router and, if so, the amount of time in seconds that the router should be used as a default router)

- Additional information for hosts, such as the hop limit and MTU that a host should use in packets that it originates

RAs are also sent in response to router solicitation messages. Router solicitation messages, which have a value of 133 in the Type field of the ICMP packet header, are sent by hosts at system startup so that the host can immediately autoconfigure without needing to wait for the next scheduled RA message. The source address is usually the unspecified IPv6 address (0:0:0:0:0:0:0:0). If the host has a configured unicast address, the unicast address of the interface that sends the router solicitation message is used as the source address in the message. The destination address is the all-routers multicast address with a scope of the link. When an RA is sent in response to a router solicitation, the destination address in the RA message is the unicast address of the source of the router solicitation message.

You can configure the following RA message parameters:

- The time interval between periodic RA messages

- The router life-time value, which indicates the usefulness of a router as the default router (for use by all nodes on a given link)

- The network prefixes in use on a given link

- The time interval between neighbor solicitation message retransmissions (on a given link)

- The amount of time that a node considers a neighbor reachable (for use by all nodes on a given link)

The configured parameters are specific to an interface. The sending of RA messages (with default values) is automatically enabled on Ethernet interfaces. For other interface types, you must enter the no ipv6 nd suppress-ra command to send RA messages. You can disable the RA message feature on individual interfaces by entering the ipv6 nd suppress-ra command.

IPv6 Neighbor Redirect Message

Routers send neighbor redirect messages to inform hosts of better first-hop nodes on the path to a destination (see Figure 3-14). A value of 137 in the Type field of the ICMP packet header identifies an IPv6 neighbor redirect message.

Figure 3-14 IPv6 Neighbor Discovery—Neighbor Redirect Message

Note A router must be able to determine the link-local address for each of its neighboring routers in order to ensure that the target address (the final destination) in a redirect message identifies the neighbor router by its link-local address. For static routing, you should specify the address of the next-hop router using the link-local address of the router. For dynamic routing, you must configure all IPv6 routing protocols to exchange the link-local addresses of neighboring routers.

After forwarding a packet, a router sends a redirect message to the source of the packet under the following circumstances:

- The destination address of the packet is not a multicast address.

- The packet was not addressed to the router.

- The packet is about to be sent out the interface on which it was received.

- The router determines that a better first-hop node for the packet resides on the same link as the source of the packet.

- The source address of the packet is a global IPv6 address of a neighbor on the same link or a link-local address.

Virtualization Support

IPv6 supports virtual routing and forwarding (VRF) instances. VRFs exist within virtual device contexts (VDCs). By default, Cisco NX-OS places you in the default VDC and default VRF unless you specifically configure another VDC and VRF. For more information, see the Cisco Nexus 7000 Series NX-OS Virtual Device Context Configuration Guide, Release 5.x, and see Chapter14, “Configuring Layer 3 Virtualization”

Licensing Requirements for IPv6

Product

License Requirement

Cisco NX-OS

IPv6 requires no license. Any feature not included in a license package is bundled with the Cisco NX-OS system images and is provided at no extra charge to you. For a complete explanation of the Cisco NX-OS licensing scheme, see the Cisco NX-OS Licensing Guide.

Prerequisites for IPv6

IPv6 has the following prerequisites:

- You must be familiar with IPv6 basics such as IPv6 addressing, IPv6 header information, ICMPv6, and the IPv6 Neighbor Discovery (ND) Protocol.

- Ensure that you follow the memory/processing guidelines when you make a device a dual-stack device (IPv4/IPv6).

Guidelines and Limitations for IPv6

IPv6 has the following configuration guidelines and limitations:

- IPv6 packets are transparent to Layer 2 LAN switches because the switches do not examine Layer 3 packet information before forwarding IPv6 frames. IPv6 hosts can be directly attached to Layer 2 LAN switches.

- You can configure multiple IPv6 global addresses within the same prefix on an interface. However, multiple IPv6 link-local addresses on an interface are not supported.

- Because RFC 3879 deprecates the use of site-local addresses, you should configure private IPv6 addresses according to the recommendations of unique local addressing (ULA) in RFC 4193.

Default Settings

Table 3-5 Default IPv6 Parameters

Parameters

Default

ND reachable time

0 milliseconds

neighbor solicitation retransmit interval

1000 milliseconds

Configuring IPv6

This section includes the following topics:

- Configuring IPv6 Addressing

- Configuring IPv6 Neighbor Discovery

- Configuring IPv6 Packet Verification

Note If you are familiar with the Cisco IOS CLI, be aware that the Cisco NX-OS commands for this feature might differ from the Cisco IOS commands that you would use.

Configuring IPv6 Addressing

You must configure an IPv6 address on an interface so that the interface can forward IPv6 traffic. When you configure a global IPv6 address on an interface, it automatically configures a link-local address and activates IPv6 for that interface.

BEFORE YOU BEGIN

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. interface ethernet number

3. ipv6 address {addr [eui64] [route-preference preference] [secondary] tag tag-id]]

or

ipv6 address ipv6-address use-link-local-only

4. (Optional) show ipv6 interface

5. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

interface ethernet number

Example:

switch(config)# interface ethernet 2/3

switch(config-if)#

Enters interface configuration mode.

Step 3

ipv6 address {addr [eui64] [route-preference preference] [secondary] tag tag-id]

or

ipv6 address ipv6-address use-link-local-only

Example:

switch(config-if)# ipv6 address 2001:0DB8::1/10

or

switch(config-if)# ipv6 address use-link-local-only

Specifies an IPv6 address assigned to the interface and enables IPv6 processing on the interface.

Entering the ipv6 address command configures global IPv6 addresses with an interface identifier (ID) in the low-order 64 bits of the IPv6 address. Only the 64-bit network prefix for the address needs to be specified; the last 64 bits are automatically computed from the interface ID.

Entering the ipv6 address use-link-local-only command configures a link-local address on the interface that is used instead of the link-local address that is automatically configured when IPv6 is enabled on the interface.

This command enables IPv6 processing on an interface without configuring an IPv6 address.

Step 4

show ipv6 interface

Example:

switch(config-if)# show ipv6 interface

(Optional) Displays interfaces configured for IPv6.

Step 5

copy running-config startup-config

Example:

switch(config-if)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to configure an IPv6 address:

switch# configure terminal

switch(config)# interface ethernet 3/1

switch(config-if)# ipv6 address ?

A:B::C:D/LEN IPv6 prefix format: xxxx:xxxx/ml, xxxx:xxxx::/ml,

xxxx::xx/128

use-link-local-only Enable IPv6 on interface using only a single link-local

address

switch(config-if)# ipv6 address 2001:db8::/64 eui64

This example shows how to display an IPv6 interface:

switch(config-if)# show ipv6 interface ethernet 3/1

Ethernet3/1, Interface status: protocol-down/link-down/admin-down, iod: 36

IPv6 address: 0dc3:0dc3:0000:0000:0218:baff:fed8:239d

IPv6 subnet: 0dc3:0dc3:0000:0000:0000:0000:0000:0000/64

IPv6 link-local address: fe80::0218:baff:fed8:239d (default)

IPv6 multicast routing: disabled

IPv6 multicast groups locally joined:

ff02::0001:ffd8:239d ff02::0002 ff02::0001 ff02::0001:ffd8:239d

IPv6 multicast (S,G) entries joined: none

IPv6 MTU: 1500 (using link MTU)

IPv6 RP inbound packet-filtering policy: none

IPv6 RP outbound packet-filtering policy: none

IPv6 inbound packet-filtering policy: none

IPv6 outbound packet-filtering policy: none

IPv6 interface statistics last reset: never

IPv6 interface RP-traffic statistics: (forwarded/originated/consumed)

Unicast packets: 0/0/0

Unicast bytes: 0/0/0

Multicast packets: 0/0/0

Multicast bytes: 0/0/0

Configuring IPv6 Neighbor Discovery

You can configure IPv6 neighbor discovery on the router. NDP enables IPv6 nodes and routers to determine the link-layer address of a neighbor on the same link, find neighboring routers, and keep track of neighbors.

BEFORE YOU BEGIN

Ensure that you are in the correct VDC (or use the switchto vdc command). You must first enable IPv6 on the interface.

SUMMARY STEPS

1. configure terminalmanaged-config-flag managed-config-flag

2. interface ethernet number

3. ipv6 nd [hop-limit hop-limit | managed-config-flag | mtu mtu | ns-interval interval | other-config-flag | prefix | ra-interval interval | ra-lifetime lifetime | reachable-time time | redirects | retrans-timer time | suppress-ra]

4. (Optional) show ipv6 nd interface

5. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

interface ethernet number

Example:

switch(config)# interface ethernet 2/31

switch(config-if)#

Enters interface configuration mode.

Step 3

ipv6 nd [hop-limit hop-limit | managed-config-flag | mtu mtu | ns-interval interval | other-config-flag | prefix | ra-interval interval | ra-lifetime lifetime | reachable-time time | redirects | retrans-timer time | suppress-ra]

Example:

switch(config-if)# ipv6 nd prefix

Neighbor discovery is enabled automatically when you configure an IPv6 address. This command enables the following additional IPv6 neighbor discovery options on the interface:

- hop-limit hop-limit —Advertises the hop limit in IPv6 neighbor discovery packets. The range is from 0 to 255.

- managed-config-flag —Advertises in ICMPv6 router-advertisement messages to use stateful address auto-configuration to obtain address information.

- mtu mtu —Advertises the maximum transmission unit (MTU) in ICMPv6 router-advertisement messages on this link. The range is from 1280 to 65535 bytes.

- ns-interval interval —Configures the retransmission interval between IPv6 neighbor solicitation messages. The range is from 1000 to 3600000 milliseconds.

- other-config-flag —Indicates in ICMPv6 router-advertisement messages that hosts use stateful auto configuration to obtain nonaddress related information.

- prefix —Advertises the IPv6 prefix in the router-advertisement messages.

- ra-interval interval —Configures the interval between sending ICMPv6 router-advertisement messages. The range is from 4 to 1800 seconds.

- ra-lifetime lifetime —Advertises the lifetime of a default router in ICMPv6 router-advertisement messages. The range is from 0 to 9000 seconds.

- reachable-time time —Advertises the time when a node considers a neighbor up after receiving a reachability confirmation in ICMPv6 router-advertisement messages. The range is from 0 to 9000 seconds.

- redirects —Enables sending ICMPv6 redirect messages.

- retrans-timer time —Advertises the time between neighbor-solicitation messages in ICMPv6 router-advertisement messages. The range is from 0 to 9000 seconds.

- suppress-ra —Disables sending ICMPv6 router-advertisement messages.

Step 4

show ipv6 nd interface

Example:

switch(config-if)# show ipv6 nd interface

(Optional) Displays interfaces configured for IPv6 neighbor discovery.

Step 5

copy running-config startup-config

Example:

switch(config-if)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to configure IPv6 neighbor discovery reachable time:

switch# configure terminal

switch(config)# interface ethernet 3/1

switch(config-if)# ipv6 nd reachable-time 10

This example shows how to display an IPv6 neighbor discovery interface:

switch(config-if)# show ipv6 nd interface ethernet 3/1

ICMPv6 ND Interfaces for VRF "default"

Ethernet3/1, Interface status: protocol-down/link-down/admin-down

IPv6 address: 0dc3:0dc3:0000:0000:0218:baff:fed8:239d

ICMPv6 active timers:

Last Neighbor-Solicitation sent: never

Last Neighbor-Advertisement sent: never

Last Router-Advertisement sent:never

Next Router-Advertisement sent in: 0.000000

Router-Advertisement parameters:

Periodic interval: 200 to 600 seconds

Send "Managed Address Configuration" flag: false

Send "Other Stateful Configuration" flag: false

Send "Current Hop Limit" field: 64

Send "MTU" option value: 1500

Send "Router Lifetime" field: 1800 secs

Send "Reachable Time" field: 10 ms

Send "Retrans Timer" field: 0 ms

Neighbor-Solicitation parameters:

NS retransmit interval: 1000 ms

ICMPv6 error message parameters:

Send redirects: false

Send unreachables: false

Optional IPv6 Neighbor Discovery

Command

Purpose

ipv6 nd hop-limit

Configures the maximum number of hops used in router advertisements and all IPv6 packets that are originated by the router.

ipv6 nd managed-config-flag

Sets the managed address configuration flag in IPv6 router advertisements.

ipv6 nd mtu

Sets the maximum transmission unit (MTU) size of IPv6 packets sent on an interface.

ipv6 nd ns-interval

Configures the interval between IPv6 neighbor solicitation retransmissions on an interface.

ipv6 nd other-config-flag

Configures the other stateful configuration flag in IPv6 router advertisements.

ipv6 nd ra-interval

Configures the interval between IPv6 router advertisement (RA) transmissions on an interface.

ipv6 nd ra-lifetime

Configures the router lifetime value in IPv6 router advertisements on an interface.

ipv6 nd reachable-time

Configures the amount of time that a remote IPv6 node is considered reachable after some reachability confirmation event has occurred.

ipv6 nd redirects

Enables ICMPv6 redirect messages to be sent.

ipv6 nd retrans-timer

Configures the advertised time between neighbor solicitation messages in router advertisements.

ipv6 nd suppress-ra

Suppresses IPv6 router advertisement transmissions on a LAN interface.

Configuring IPv6 Packet Verification

Cisco NX-OS supports an Intrusion Detection System (IDS) that checks for IPv6 packet verification. You can enable or disable these IDS checks.

To enable IDS checks, use the following commands in global configuration mode:

Command

Purpose

hardware ip verify address {destination zero | identical | reserved | source multicast}

Performs the following IDS checks on the IPv6 address:

- destination zero —Drops IPv6 packets if the destination IP address is ::.

- identical —Drops IPv6 packets if the source IPv6 address is identical to the destination IPv6 address.

- reserved —Drops IPv6 packets if the IPv6 address is ::1.

- source multicast —Drops IPv6 packets if the IPv6 source address is in the FF00::/8 range (multicast).

hardware ipv6 verify length {consistent | maximum {max-frag | max-tcp | udp}}

Performs the following IDS checks on the IPv6 address:

- consistent —Drops IPv6 packets where the Ethernet frame size is greater than or equal to the IPv6 packet length plus the Ethernet header.

- maximum max-frag —Drops IPv6 packets if the formula (IPv6 Payload Length – IPv6 Extension Header Bytes) + (Fragment Offset * 8) is greater than 65536.

- maximum max-tcp —Drops IPv6 packets if the TCP length is greater than the IP payload length.

- maximum udp —Drops IPv6 packets if the IPv6 payload length is less than the UDP packet length.

hardware ipv6 verify tcp tiny-frag

Drops TCP packets if the IPv6 fragment offset is 1, or if the IPv6 fragment offset is 0 and the IP payload length is less than 16.

hardware ipv6 verify version

Drops IPv6 packets if the EtherType is not set to 6 (IPv6).

Use the show hardware forwarding ip verify command to display the IPv6 packet verification configuration.

Verifying the IPv6 Configuration

To display the IPv6 configuration, perform one of the following tasks:

Command

Purpose

show hardware forwarding ip verify

Displays the IPv4 and IPv6 packet verification configuration.

show ipv6 interface

Displays IPv6-related interface information.

show ipv6 adjacency

Displays the adjacency table.

show ipv6 icmp

Displays ICMPv6 information.

show ipv6 nd

Displays IPv6 neighbor discovery interface information.

show ipv6 neighbor

Displays IPv6 neighbor entry.

Configuration Examples for IPv6

- Related Documents

- Standards

Related Documents

Related Topic

Document Title

IPv6 CLI commands

Cisco Nexus 7000 Series NX-OS Unicast Routing Command Reference, Release 5.x

Standards

Standards

Title

No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.

—

Feature History for IPv6

Table 3-6 lists the release history for this feature.

Table 3-6 Feature History for IPv6

Feature Name

Releases

Feature Information

IPv6 path MTU discovery

5.0(2)

Added support for IPv6 path MTU discovery.

IPv6

4.1(3)

Changed the platform {ip | ipv6} verify command to the hardware {ip | ipv6} verify command.

IPv6 address

4.0(3)

Added the tag keyword to the ipv6 address command.

IPv6

4.0(1)

This feature was introduced.

Configuring IS-IS

This chapter describes how to configure Integrated Intermediate System-to-Intermediate System (IS-IS) on the Cisco NX-OS device.

This chapter includes the following sections:

- Information About IS-IS

- Licensing Requirements for IS-IS

- Prerequisites for IS-IS

- Guidelines and Limitations for IS-IS

- Default Settings

- Configuring IS-IS

- Verifying the IS-IS Configuration

- Monitoring IS-IS

- Configuration Examples for IS-IS

- Related Topics

- Additional References

- Feature History for IS-IS

Information About IS-IS

IS-IS is an Interior Gateway Protocol (IGP) based on Standardization (ISO)/International Engineering Consortium (IEC) 10589. Cisco NX-OS supports Internet Protocol version 4 (IPv4). IS-IS is a dynamic link-state routing protocol that can detect changes in the network topology and calculate loop-free routes to other nodes in the network. Each router maintains a link-state database that describes the state of the network and sends packets on every configured link to discover neighbors. IS-IS floods the link-state information across the network to each neighbor. The router also sends advertisements and updates on the link-state database through all the existing neighbors.

Note Cisco NX-OS does not support IPv6 for IS-IS.

This section includes the following topics:

- IS-IS Overview

- IS-IS Authentication

- Mesh Groups

- Overload Bit

- Route Summarization

- Route Redistribution

- Load Balancing

- BFD

- Virtualization Support

- High Availability and Graceful Restart

- Multiple IS-IS Instances

IS-IS Overview

IS-IS sends ahello packet out every configured interface to discover IS-IS neighbor routers. The hello packet contains information, such as the authentication, area, and supported protocols, which the receiving interface uses to determine compatibility with the originating interface. The hello packets are also padded to ensure that IS-IS establishes adjacencies only with interfaces that have matching maximum transmission unit (MTU) settings. Compatible interfaces form adjacencies, which update routing information in the link-state database through link-state update messages (LSPs). By default, the router sends a periodic LSP refresh every 10 minutes and the LSPs remain in the link-state database for 20 minutes (the LSP lifetime). If the router does not receive an LSP refresh before the end of the LSP lifetime, the router deletes the LSP from the database.

The LSP interval must be less than the LSP lifetime or the LSPs time out before they are refreshed.

IS-IS sends periodic hello packets to adjacent routers. If you configure transient mode for hello packets, these hello packets do not include the excess padding used before IS-IS establishes adjacencies. If the MTU value on adjacent routers changes, IS-IS can detect this change and send padded hello packets for a period of time. IS-IS uses this feature to detect mismatched MTU values on adjacent routers. For more information, see the “Configuring the Transient Mode for Hello Padding” section.

IS-IS Areas

You can design IS-IS networks as a single area that includes all routers in the network or as multiple areas that connect into a backbone or Level 2 area. Routers in a nonbackbone area are Level 1 routers that establish adjacencies within a local area (intra-area routing). Level 2 area routers establish adjacencies to other Level 2 routers and perform routing between Level 1 areas (inter-area routing). A router can have both Level 1 and Level 2 areas configured. These Level 1/Level 2 routers act as area border routers that route information from the local area to the Level 2 backbone area (see Figure 9-1).

Within a Level 1 area, routers know how to reach all other routers in that area. The Level 2 routers know how to reach other area border routers and other Level 2 routers. Level 1/Level 2 routers straddle the boundary between two areas, routing traffic to and from the Level 2 backbone area. Level1/Level2 routers use the attached (ATT) bit signal Level 1 routers to set a default route to this Level1/Level2 router to connect to the Level 2 area.

In some instances, such as when you have two or more Level1/Level 2 routers in an area, you may want to control which Level1/Level2 router that the Level 1 routers use as the default route to the Level 2 area. You can configure which Level1/Level2 router sets the attached bit. For more information, see the “Verifying the IS-IS Configuration” section.

Each IS-IS instance in Cisco NX-OS supports either a single Level 1 or Level 2 area, or one of each. By default, all IS-IS instances automatically support Level 1 and Level 2 routing.

Figure 9-1 IS-IS Network Divided into Areas

An autonomous system boundary router (ASBR) advertises external destinations throughout the IS-IS autonomous system. External routes are the routes redistributed into IS-IS from any other protocol.

NET and System ID

Each IS-IS instance has an associated network entity title (NET). The NET is comprised of the IS-IS system ID, which uniquely identifies this IS-IS instance in the area and the area ID. For example, if the NET is 47.0004.004d.0001.0001.0c11.1111.00, the system ID is 0000.0c11.1111.00 and the area is ID 47.0004.004d.0001.

Designated Intermediate System

IS-IS uses a designated intermediate system (DIS) in broadcast networks to prevent each router from forming unnecessary links with every other router on the broadcast network. IS-IS routers send LSPs to the DIS, which manages all the link-state information for the broadcast network. You can configure the IS-IS priority that IS-IS uses to select the DIS in an area.

Note No DIS is required on a point-to-point network.

IS-IS Authentication

You can configure authentication to control adjacencies and the exchange of LSPs. Routers that want to become neighbors must exchange the same password for their configured level of authentication. IS-IS blocks a router that does not have the correct password. You can configure IS-IS authentication globally or for an individual interface for Level 1, Level 2, or both Level 1/Level 2 routing.

IS-IS supports the following authentication methods:

- Clear text—All packets exchanged carry a cleartext 128-bit password.

- MD5 digest—All packets exchanged carry a message digest that is based on a 128-bit key.

To provide protection against passive attacks, IS-IS never sends the MD5 secret key as cleartext through the network. In addition, IS-IS includes a sequence number in each packet to protect against replay attacks.

You can use also keychains for hello and LSP authentication. See the Cisco Nexus 7000 Series NX-OS Security Configuration Guide, Release 5.x, for information on keychain management.

Mesh Groups

A mesh group is a set of interfaces in which all routers reachable over the interfaces have at least one link to every other router. Many links can fail without isolating one or more routers from the network.

In normal flooding, an interface receives a new LSP and floods the LSP out over all other interfaces on the router. With mesh groups, when an interface that is part of a mesh group receives a new LSP, the interface does not flood the new LSP over the other interfaces that are part of that mesh group.

Note You may want to limit LSPs in certain mesh network topologies to improve network scalability. Limiting LSP floods might also reduce the reliability of the network (in case of failures). For this reason, we recommend that you use mesh groups only if specifically required, and then only after you make a careful network design.

You can also configure mesh groups in block mode for parallel links between routers. In this mode, all LSPs are blocked on that interface in a mesh group after the routers initially exchange their link-state information.

Overload Bit

IS-IS uses the overload bit to tell other routers not to use the local router to forward traffic but to continue routing traffic destined for that local router.

You may want to use the overload bit in these situations:

- The router is in a critical condition.

- Graceful introduction and removal of the router to/from the network.

- Other (administrative or traffic engineering) reasons such as waiting for BGP convergence.

Route Summarization

You can configure a summary aggregate address. Route summarization simplifies route tables by replacing a number of more-specific addresses with an address that represents all the specific addresses. For example, you can replace 10.1.1.0/24, 10.1.2.0/24, and 10.1.3.0/24 with one summary address, 10.1.0.0/16.

If more specific routes are in the routing table, IS-IS advertises the summary address with a metric equal to the minimum metric of the more specific routes.

Note Cisco NX-OS does not support automatic route summarization.

Route Redistribution

You can use IS-IS to redistribute static routes, routes learned by other IS-IS autonomous systems, or routes from other protocols. You must configure a route map with the redistribution to control which routes are passed into IS-IS. A route map allows you to filter routes based on attributes such as the destination, origination protocol, route type, route tag, and so on. For more information, see Chapter16, “Configuring Route Policy Manager”

Whenever you redistribute routes into an IS-IS routing domain, Cisco NX-OS does not, by default, redistribute the default route into the IS-IS routing domain. You can generate a default route into IS-IS, which can be controlled by a route policy.

You also configure the default metric that is used for all imported routes into IS-IS.

Load Balancing

You can use load balancing to allow a router to distribute traffic over all the router network ports that are the same distance from the destination address. Load balancing increases the utilization of network segments and increases the effective network bandwidth.

Cisco NX-OS supports the Equal Cost Multiple Paths (ECMP) feature with up to 16 equal-cost paths in the IS-IS route table and the unicast RIB. You can configure IS-IS to load balance traffic across some or all of those paths.

BFD

This feature supports bidirectional forwarding detection (BFD). BFD is a detection protocol designed to provide fast forwarding-path failure detection times. BFD provides subsecond failure detection between two adjacent devices and can be less CPU-intensive than protocol hello messages because some of the BFD load can be distributed onto the data plane on supported modules. See the Cisco Nexus 7000 Series NX-OS Interfaces Configuration Guide, Release 5.x, for more information.

Virtualization Support

Cisco NX-OS supports multiple instances of the IS-IS protocol that runs on the same system. IS-IS supports virtual routing and forwarding (VRF) instances. VRFs exist within virtual device contexts (VDCs). You can configure up to four IS-IS instances in a VDC.

By default, Cisco NX-OS places you in the default VDC and default VRF unless you specifically configure another VDC and VRF. See the Cisco Nexus 7000 Series NX-OS Virtual Device Context Configuration Guide, Release 5.x, and Chapter14, “Configuring Layer 3 Virtualization”

High Availability and Graceful Restart

Cisco NX-OS provides a multilevel high-availability architecture. IS-IS supports stateful restart, which is also referred to as non-stop routing (NSR). If IS-IS experiences problems, it attempts to restart from its previous run-time state. The neighbors would not register any neighbor event in this case. If the first restart is not successful and another problem occurs, IS-IS attempts a graceful restart as per RFC 3847. A graceful restart, or non-stop forwarding (NSF), allows IS-IS to remain in the data forwarding path through a process restart. When the restarting IS-IS interface is operational again, it rediscovers its neighbors, establishes adjacency, and starts sending its updates again. At this point, the NSF helpers recognize that the graceful restart has finished.

A stateful restart is used in the following scenarios:

- First recovery attempt after process experiences problems

- ISSU

- User-initiated switchover using the system switchover command

A graceful restart is used in the following scenarios:

- Second recovery attempt after the process experiences problems within a 4-minute interval

- Manual restart of the process using the restart isis command

- Active supervisor removal

- Active supervisor reload using the reload module active-sup command

Note Graceful restart is on by default, and we strongly recommended that it not be disabled.

Multiple IS-IS Instances

Cisco NX-OS supports a maximum of four instances of the IS-IS protocol that run on the same node. You cannot configure multiple instances over the same interface. Every instance uses the same system router ID.

Licensing Requirements for IS-IS

The following table shows the licensing requirements for this feature:

Product

License Requirement

Cisco NX-OS

IS-IS requires an Enterprise Services license. For a complete explanation of the Cisco NX-OS licensing scheme and how to obtain and apply licenses, see the Cisco NX-OS Licensing Guide.

Prerequisites for IS-IS

IS-IS has the following prerequisites:

- You must enable IS-IS (see the “Enabling the IS-IS Feature” section).

- If you configure VDCs, install the Advanced Services license and enter the desired VDC (see the Cisco Nexus 7000 Series NX-OS Virtual Device Context Configuration Guide, Release 5.x).

Guidelines and Limitations for IS-IS

IS-IS has the following configuration guidelines and limitations:

- You can configure a maximum of four IS-IS instances per VDC.

- Because the default reference bandwidth is different for Cisco NX-OS and Cisco IOS, the advertised tunnel IS-IS metric is different for these two operating systems.

Default Settings

Table 9-1 Default IS-IS Parameters

Parameters

Default

Administrative distance

115

Area level

Level-1-2

DIS priority

64

Graceful restart

Enabled

Hello multiplier

3

Hello padding

Enabled

Hello time

10 seconds

IS-IS feature

Disabled

LSP interval

33

LSP MTU

1492

Maximum LSP lifetime

1200 seconds

Maximum paths

4

Metric

40

Reference bandwidth

40 Gbps

Configuring IS-IS

To configure IS-IS, follow these steps:

Step 1 Enable the IS-IS feature (see the “Enabling the IS-IS Feature” section).

Step 2 Create an IS-IS instance (see the “Creating an IS-IS Instance” section).

Step 3 Add an interface to the IS-IS instance (see the “Configuring IS-IS on an Interface” section).

Step 4 Configure optional features, such as authentication, mesh groups, and dynamic host exchange.

This section contains the following topics:

- IS-IS Configuration Modes

- Enabling the IS-IS Feature

- Creating an IS-IS Instance

- Restarting an IS-IS Instance

- Shutting Down IS-IS

- Configuring IS-IS on an Interface

- Shutting Down IS-IS on an Interface

- Configuring IS-IS Authentication in an Area

- Configuring IS-IS Authentication on an Interface

- Configuring a Mesh Group

- Configuring a Designated Intermediate System

- Configuring Dynamic Host Exchange

- Setting the Overload Bit

- Configuring the Attached Bit

- Configuring the Transient Mode for Hello Padding

- Configuring a Summary Address

- Configuring Redistribution

- Limiting the Number of Redistributed Routes

- Configuring a Graceful Restart

- Configuring Virtualization

- Tuning IS-IS

Note If you are familiar with the Cisco IOS CLI, be aware that the Cisco NX-OS commands for this feature might differ from the Cisco IOS commands that you would use.

IS-IS Configuration Modes

The following sections show how to enter each of the configuration modes. From a mode, you can enter the ? command to display the commands available in that mode.

This section includes the following topics:

- Router Configuration Mode

- Router Address Family Configuration Mode

Router Configuration Mode

This example shows how to enter router configuration mode:

switch#: configure terminal

switch(config)# router isis isp

switch(config-router)#

Router Address Family Configuration Mode

This example shows how to enter router address family configuration mode:

switch(config)# router isis isp

switch(config-router)# address-family ipv4 unicast

switch(config-router-af)#

Enabling the IS-IS Feature

You must enable the IS-IS feature before you can configure IS-IS.

BEFORE YOU BEGIN

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. feature isis

3. (Optional) show feature

4. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

feature isis

Example:

switch(config)# feature isis

Enables the IS-IS feature.

Step 3

show feature

Example:

switch(config)# show feature

(Optional) Displays enabled and disabled features.

Step 4

copy running-config startup-config

Example:

switch(config)# copy running-config startup-config

(Optional) Saves this configuration change.

To disable the IS-IS feature and remove all associated configuration, use the following command in configuration mode.

Command

Purpose

no feature isis

Example:

switch(config)# no feature isis

Disables the IS-IS feature and removes all associated configuration.

Creating an IS-IS Instance

You can create an IS-IS instance and configure the area level for that instance.

BEFORE YOU BEGIN

You must enable IS-IS (see the “Enabling the IS-IS Feature” section).

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. router isis instance-tag

3. net network-entity-title

4. (Optional) is-type {level-1 | level-2 | level-1-2}

5. (Optional) show isis [vrf vrf-name] process

6. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

router isis instance-tag

Example:

switch(config)# router isis Enterprise

switch(config-router)#

Creates a new IS-IS instance with the configured instance tag.

Step 3

net network-entity-title

Example:

switch(config-router)# net 47.0004.004d.0001.0001.0c11.1111.00

Configures the NET for this IS-IS instance.

Step 4

is-type {level-1 | level-2 | level-1-2}

Example:

switch(config-router)# is-type level-2

(Optional) Configures the area level for this IS-IS instance. The default is level-1-2.

Step 5

show isis [vrf vrf-name] process

Example:

switch(config)# show isis process

(Optional) Displays a summary of IS-IS information for all IS-IS instances.

Step 6

copy running-config startup-config

Example:

switch(config)# copy running-config startup-config

(Optional) Saves this configuration change.

To remove the IS-IS instance and the associated configuration, use the following command in configuration mode.

Command

Purpose

no router isis instance-tag

Example:

switch(config)# no router isis Enterprise

Deletes the IS-IS instance and all associated configuration.

Note You must also remove any IS-IS commands that are configured in interface mode to completely remove all configuration for the IS-IS instance.

Command

Purpose

distance value

Example:

switch(config-router)# distance 30

Sets the administrative distance for IS-IS. The range is from 1 to 255. The default is 115. See the “Administrative Distance” section.

log-adjacency-changes

Example:

switch(config-router)# log-adjacency-changes

Sends a system message whenever an IS-IS neighbor changes the state.

lsp-mtu size

Example:

switch(config-router)# lsp-mtu 600

Sets the MTU for LSPs in this IS-IS instance. The range is from 128 to 4352 bytes. The default is 1492.

maximum-paths number

Example:

switch(config-router)# maximum-paths 6

Configures the maximum number of equal-cost paths that IS-IS maintains in the route table. The range is from 1 to 16. The default is 4.

reference-bandwidth bandwidth-value {Mbps | Gbps}

Example:

switch(config-router)# reference-bandwidth 100 Gbps

Sets the default reference bandwidth used for calculating the IS-IS cost metric. The range is from 1 to 4000 Gbps. The default is 40 Gbps.

The following example shows how to create an IS-IS instance in a level 2 area:

switch# configure terminal

switch(config)# router isis Enterprise

switch(config-router)# net 47.0004.004d.0001.0001.0c11.1111.00

switch(config-router)# is-type level 2

switch(config-router)# copy running-config startup-config

To clear neighbor statistics and remove adjacencies, use the following command in router configuration mode:

Command

Purpose

clear isis [instance-tag] adjacency [* | system-id | interface]

Example:

switch(config-if)# clear isis adjacency *

Clears neighbor statistics and removed adjacencies for this IS-IS instance.

Restarting an IS-IS Instance

You can restart an IS-IS instance. This action clears all neighbors for the instance.

Command

Purpose

restart isis instance-tag

Example:

switch(config)# restart isis Enterprise

Shutting Down IS-IS

You can shut down the IS-IS instance. This action disables this IS-IS instance and retains the configuration.

To shut down the IS-IS instance, use the following command in router configuration mode:

Command

Purpose

shutdown

Example:

switch(config-router)# shutdown

Disables the IS-IS instance.

Configuring IS-IS on an Interface

You can add an interface to an IS-IS instance.

BEFORE YOU BEGIN

You must enabled IS-IS (see the “Enabling the IS-IS Feature” section).

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. interface interface-type slot/port

3. (Optional) medium {broadcast | p2p}

4. ip router isis instance-tag

5. (Optional) show isis [vrf vrf-name] [instance-tag] interface [interface-type slot/port]

6. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

interface interface-type slot/port

Example:

switch(config)# interface ethernet 1/2

switch(config-if)#

Enters interface configuration mode.

Step 3

medium {broadcast | p2p}

Example:

switch(config-if)# medium p2p

(Optional) Configures the broadcast or point-to-point mode for the interface. IS-IS inherits this mode.

Step 4

ip router isis instance-tag

Example:

switch(config-if)# ip router isis Enterprise

Associates this IPv4 interface with an IS-IS instance.

Step 5

show isis [vrf vrf-name] [instance-tag] interface [interface-type slot/port]

Example:

switch(config)# show isis Enterprise ethernet 1/2

(Optional) Displays IS-IS information for an interface.

Step 6

copy running-config startup-config

Example:

switch(config)# copy running-config startup-config

(Optional) Saves this configuration change.

You can configure the following optional parameters for IS-IS in interface mode:

Command

Purpose

isis circuit-type {level-1 | level-2 | level-1-2}

Example:

switch(config-if)# isis circuit-type level-2

Sets the type of adjacency that this interface participates in. Use this command only for routers that participate in both Level 1 and Level 2 areas.

isis metric value {level-1 | level-2}

Example:

switch(config-if)# isis metric 30

Sets the IS-IS metric for this interface. The range is from 1 to 16777214. The default is 10.

isis passive {level-1 | level-2 | level-1-2}

Example:

switch(config-if)# isis passive level-2

Prevents the interface from forming adjacencies but still advertises the prefix associated with the interface.

This example shows how to add Ethernet 1/2 interface to an IS-IS instance:

switch# configure terminal

switch(config)# interface ethernet 1/2

switch(config-if)# ip router isis Enterprise

switch(config-if)# copy running-config startup-config

Shutting Down IS-IS on an Interface

You can gracefully shut down IS-IS on an interface. This action removes all adjacencies and stops IS-IS traffic on this interface but preserves the IS-IS configuration.

To disable IS-IS on an interface, use the following command in interface configuration mode:

Command

Purpose

switch(config-if)# isis shutdown

Example:

switch(config-router)# isis shutdown

Disables IS-IS on this interface. The IS-IS interface configuration remains.

Configuring IS-IS Authentication in an Area

You can configure IS-IS to authenticate LSPs in an area.

BEFORE YOU BEGIN

You must enable IS-IS (see the “Enabling the IS-IS Feature” section).

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. router isis instance-tag

3. authentication-type {cleartext | md5} {level-1 | level-2}

4. authentication key-chain key {level-1 | level-2}

5. (Optional) authentication-check {level-1 | level-2}

6. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

router isis instance-tag

Example:

switch(config)# router isis Enterprise

switch(config-router)#

Creates a new IS-IS instance with the configured instance tag.

Step 3

authentication-type {cleartext | md5} {level-1 | level-2}

Example:

switch(config-router)# authentication-type cleartext level-2

Sets the authentication method used for a Level 1 or Level 2 area as cleartext or as an MD5 authentication digest.

Step 4

authentication key-chain key {level-1 | level-2}

Example:

switch(config-router)# authentication key-chain ISISKey level-2

Configures the authentication key used for an IS-IS area-level authentication.

Step 5

authentication-check {level-1 | level-2}

Example:

switch(config-router)# authentication-check level-2

(Optional) Enables checking the authentication parameters in a received packet.

Step 6

copy running-config startup-config

Example:

switch(config-router)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to configure cleartext authentication on an IS-IS instance:

switch# configure terminal

switch(config)# router isis Enterprise

switch(config-router)# authentication-type cleartext level-2

switch(config-router)# authentication key-chain ISISKey level-2

switch(config-router)# copy running-config startup-config

Configuring IS-IS Authentication on an Interface

You can configure IS-IS to authenticate Hello packets on an interface.

BEFORE YOU BEGIN

You must enable IS-IS (see the “Enabling the IS-IS Feature” section).

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. interface interface-type slot/port

3. isis authentication-type {cleartext | md5} {level-1 | level-2}

4. isis authentication key-chain key {level-1 | level-2}

5. (Optional) isis authentication-check {level-1 | level-2}

6. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

interface interface-type slot/port

Example:

switch(config)# interface ethernet 1/2

switch(config-if)#

Enters interface configuration mode.

Step 3

isis authentication-type {cleartext | md5} {level-1 | level-2}

Example:

switch(config-if)# isis authentication-type cleartext level-2

Sets the authentication type for IS-IS on this interface as cleartext or as an MD5 authentication digest.

Step 4

isis authentication key-chain key {level-1 | level-2}

Example:

switch(config-if)# isis authentication-key ISISKey level-2

Configures the authentication key used for IS-IS on this interface.

Step 5

isis authentication-check {level-1 | level-2}

Example:

switch(config-if)# isis authentication-check

Step 6

copy running-config startup-config

Example:

switch(config-if)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to configure cleartext authentication on an IS-IS instance:

switch# configure terminal

switch(config)# interface ethernet 1/2

switch(config-if)# isis authentication-type cleartext level-2

switch(config-if)# isis authentication key-chain ISISKey

switch(config-if)# copy running-config startup-config

Configuring a Mesh Group

You can add an interface to a mesh group to limit the amount of LSP flooding for interfaces in that mesh group. You can optionally block all LSP flooding on an interface in a mesh group.

To add an interface to a mesh group, use the following command in interface configuration mode:

Command

Purpose

isis mesh-group {blocked | mesh-id}

Example:

switch(config-if)# isis mesh-group 1

Adds this interface to a mesh group. The range is from 1 to 4294967295.

Configuring a Designated Intermediate System

You can configure a router to become the designated intermediate system (DIS) for a multiaccess network by setting the interface priority.

Command

Purpose

isis priority number {level-1 | level-2}

Example:

switch(config-if)# isis priority 100 level-1

Sets the priority for DIS selection. The range is from 0 to 127. The default is 64.

Configuring Dynamic Host Exchange

You can configure IS-IS to map between the system ID and the hostname for a router using dynamic host exchange.

Command

Purpose

hostname dynamic

Example:

switch(config-router)# hostname dynamic

Enables dynamic host exchange.

Setting the Overload Bit

You can configure the router to signal other routers not to use this router as an intermediate hop in their shortest path first (SPF) calculations. You can optionally configure the overload bit temporarily on startup, until BGP converges.

In addition to setting the overload bit, you might also want to suppress certain types of IP prefix advertisements from LSPs for Level 1 or Level 2 traffic.

To set the overload bit, use the following command in router configuration mode:

Command

Purpose

set-overload-bit {always | on-startup {seconds | wait-for bgp as-number}} [suppress [interlevel | external]]

Example:

switch(config-router)# set-overload-bit on-startup 30

Sets the overload bit for IS-IS. The seconds range is from 5 to 86400.

Configuring the Attached Bit

You can configure the attached bit to control which Level 1/Level 2 router that the Level 1 routers use as the default route to the Level 2 area. If you disable setting the attached bit, the Level 1 routers do not use this Level 1/Level 2 router to reach the Level 2 area.

Command

Purpose

[no] attached-bit

Example:

switch(config-router)# no attached-bit

Configures the Level 1/Level 2 router to set the attached bit. This feature is enabled by default.

Configuring the Transient Mode for Hello Padding

You can configure the transient mode for hello padding to pad hello packets when IS-IS establishes adjacency and remove that padding after IS-IS establishes adjacency.

Command

Purpose

[no] isis hello-padding

Example:

switch(config-if)# no isis hello-padding

Pads the hello packet to the full MTU. The default is enabled. Use the no form of this command to configure the transient mode of hello padding.

Configuring a Summary Address

You can create aggregate addresses that are represented in the routing table by a summary address. One summary address can include multiple groups of addresses for a given level. Cisco NX-OS advertises the smallest metric of all the more-specific routes.

BEFORE YOU BEGIN

You must enable IS-IS (see the “Enabling the IS-IS Feature” section).

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. router isis instance-tag

3. address-family ipv4 {unicast | multicast}

4. summary-address ip-prefix/mask-len {level-1 | level-2 | level-1-2}

5. (Optional) show isis [vrf vrf-name] ip summary-address ip-prefix [longer-prefixes]

6. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

router isis instance-tag

Example:

switch(config)# router isis Enterprise

switch(config-router)#

Creates a new IS-IS instance with the configured instance tag.

Step 3

address-family ipv4 {unicast | multicast}

Example:

switch(config-router)# address-family ipv4 unicast

switch(config-router-af)#

Enters address family configuration mode.

Step 4

summary-address ip-prefix/mask-len {level-1 | level-2 | level-1-2}

Example:

switch(config-router-af)# summary-address 192.0.2.0/24 level-2

Configures a summary address for an ISIS area for IPv4 addresses.

Step 5

show isis [vrf vrf-name] ip summary-address ip-prefix [longer-prefixes]]

Example:

switch(config-if)# show isis ip summary-address

(Optional) Displays IS-IS IPv4 summary address information.

Step 6

copy running-config startup-config

Example:

switch(config--if)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to configure an IPv4 unicast summary address for IS-IS:

switch# configure terminal

switch(config)# router isis Enterprise

switch(config-router)# address-family ipv4 unicast

switch(config-router-af)# summary-address 192.0.2.0/24 level-2

switch(config-router-af)# copy running-config startup-config

Configuring Redistribution

You can configure IS-IS to accept routing information from another routing protocol and redistribute that information through the IS-IS network. You can optionally assign a default route for redistributed routes.

BEFORE YOU BEGIN

You must enable IS-IS (see the “Enabling the IS-IS Feature” section).

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. router isis instance-tag

3. address-family ipv4 unicast

4. redistribute {bgp as | direct |{eigrp | isis | ospf | ospfv3 | rip} instance-tag | static} route-map map-name

5. (Optional) default-information originate [always] [route-map map-name]

6. (Optional) distribute {level-1 | level-2} into {level-1 | level-2} {route-map route-map | all}

7. (Optional) show isis [vrf vrf-name] ip route ip-prefix [detail | longer-prefixes [summary | detail]]

8. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

router isis instance-tag

Example:

switch(config)# router isis Enterprise

switch(config-router)#

Creates a new IS-IS instance with the configured instance tag.

Step 3

address-family ipv4 unicast

Example:

switch(config-router)# address-family ipv4 unicast

switch(config-router-af)#

Enters address family configuration mode.

Step 4

redistribute {bgp as | {eigrp | isis | ospf | ospfv3 | rip} instance-tag | static | direct} route-map map-name

Example:

switch(config-router-af)# redistribute eigrp 201 route-map ISISmap

Redistributes routes from other protocols into IS-IS. See the “Configuring Route Maps” section for more information about route maps.

Step 5

default-information originate [always] [route-map map-name]

Example:

switch(config-router-af)# default-information originate always

(Optional) Generates a default route into IS-IS.

Step 6

distribute {level-1 | level-2} into {level-1 | level-2} {route-map route-map | all}

Example:

switch(config-router-af)# distribute level-1 into level-2 all

(Optional) Redistributes routes from one IS-IS level to the other IS-IS level.

Step 7

show isis [vrf vrf-name] ip route ip-prefix [detail | longer-prefixes [summary | detail]]

Example:

switch(config-router-af)# show isis ip route

(Optional) Shows the routes IS-IS.

Step 8

copy running-config startup-config

Example:

switch(config-router-af)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to redistribute EIGRP into IS-IS:

switch# configure terminal

switch(config)# router isis Enterprise

switch(config-router)# address-family ipv4 unicast

switch(config-router-af)# redistribute eigrp 201 route-map ISISmap

switch(config-router-af)# copy running-config startup-config

Limiting the Number of Redistributed Routes

Route redistribution can add many routes to the IS-IS route table. You can configure a maximum limit to the number of routes accepted from external protocols. IS-IS provides the following options to configure redistributed route limits:

- Fixed limit—Logs a message when IS-IS reaches the configured maximum. IS-IS does not accept any more redistributed routes. You can optionally configure a threshold percentage of the maximum where IS-IS logs a warning when that threshold is passed.

- Warning only—Logs a warning only when IS-IS reaches the maximum. IS-IS continues to accept redistributed routes.

- Withdraw—Starts the timeout period when IS-IS reaches the maximum. After the timeout period, IS-IS requests all redistributed routes if the current number of redistributed routes is less than the maximum limit. If the current number of redistributed routes is at the maximum limit, IS-IS withdraws all redistributed routes. You must clear this condition before IS-IS accepts more redistributed routes. You can optionally configure the timeout period.

BEFORE YOU BEGIN

You must enable IS-IS (see the “Enabling the IS-IS Feature” section).

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. router is-is instance-tag

3. redistribute {bgp id | direct | eigrp id | isis id | ospf id | rip id | static} route-map map-name

4. redistribute maximum-prefix max [threshold] [warning-only | withdraw [num-retries timeout]]

5. (Optional) show running-config isis

6. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

router eigrp instance-tag

Example:

switch(config)# router isis Enterprise

switch(config-router)#

Creates a new IS-IS instance with the configured instance tag.

Step 3

redistribute {bgp id | direct | eigrp id | isis id | ospf id | rip id | static} route-map map-name

Example:

switch(config-router)# redistribute bgp route-map FilterExternalBGP

Redistributes the selected protocol into IS-IS through the configured route map.

Step 4

redistribute maximum-prefix max [threshold] [warning-only | withdraw [num-retries timeout]]

Example:

switch(config-router)# redistribute maximum-prefix 1000 75 warning-only

Specifies a maximum number of prefixes that IS-IS distributes. The range is from 0 to 65536. You can optionally specify the following:

- threshold —Percent of maximum prefixes that triggers a warning message.

- warning-only —Logs an warning message when the maximum number of prefixes is exceeded.

- withdraw —Withdraws all redistributed routes. You can optionally try to retrieve the redistributed routes. The num-retries range is from 1 to 12. The timeout is 60 to 600 seconds. The default is 300 seconds. Use the clear isis redistribution command if all routes are withdrawn.

Step 5

show running-config isis

Example:

switch(config-router)# show running-config isis

(Optional) Displays the IS-IS configuration.

Step 6

copy running-config startup-config

Example:

switch(config-router)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to limit the number of redistributed routes into IS-IS:

switch# configure terminal

switch(config)# router eigrp isis Enterprise

switch(config-router)# redistribute bgp route-map FilterExternalBGP

switch(config-router)# redistribute maximum-prefix 1000 75

Configuring a Graceful Restart

You can configure a graceful restart for IS-IS.

BEFORE YOU BEGIN

You must enable IS-IS (see the “Enabling the IS-IS Feature” section).

Create the VDCs and VRFs.

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. router isis instance-tag

3. graceful-restart

4. graceful-restart t3 manual time

5. (Optional) show running-config isis

6. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

router isis instance-tag

Example:

switch(config)# router isis Enterprise

switch(config-router)#

Creates a new IS-IS process with the configured name.

Step 3

graceful-restart

Example:

switch(config-router)# graceful-restart

Step 4

graceful-restart t3 manual time

Example:

switch(config-router)# graceful-restart t3 manual 300

Configures the graceful restart T3 timer. The range is from 30 to 65535 seconds. The default is 60.

Step 5

show running-config isis

Example:

switch(config-router)# show running-config isis

(Optional) Displays the IS-IS configuration.

Step 6

copy running-config startup-config

Example:

switch(config-router)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to enable a graceful restart:

switch# configure terminal

switch(config)# router isis Enterprise

switch(config-router)# graceful-restart

switch(config-router)# copy running-config startup-config

Configuring Virtualization

You can configure multiple IS-IS instances in each VDC. You can also create multiple VRFs within each VDC and use the same or multiple IS-IS instances in each VRF. You assign an IS-IS interface to a VRF.

You must configure a NET for the configured VRF.

Note Configure all other parameters for an interface after you configure the VRF for an interface. Configuring a VRF for an interface deletes all the configuration for that interface.

BEFORE YOU BEGIN

You must enable IS-IS (see the “Enabling the IS-IS Feature” section).

Create the VDCs.

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. vrf context vrf_name

3. exit

4. router isis instance-tag

5. (Optional) vrf vrf_name

6. net network-entity-title

7. exit

8. interface type slot/port

9. vrf member vrf-name

10. ip address ip-prefix/length

11. ip router isis instance-tag

12. (Optional) show isis [vrf vrf-name] [instance-tag] interface [interface-type slot/port]

13. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

vrf context vrf-name

Example:

switch(config)# vrf context RemoteOfficeVRF

switch(config-vrf)#

Creates a new VRF and enters VRF configuration mode.

Step 3

exit

Example:

switch(config-vrf)# exit

switch(config)#

Exits VRF configuration mode.

Step 4

router isis instance-tag

Example:

switch(config)# router isis Enterprise

switch(config-router)#

Creates a new IS-IS instance with the configured instance tag.

Step 5

vrf vrf-name

Example:

switch(config-router)# vrf RemoteOfficeVRF

switch(config-router-vrf)#

(Optional) Enters VRF configuration mode.

Step 6

net network-entity-title

Example:

switch(config-router-vrf)# net 47.0004.004d.0001.0001.0c11.1111.00

Configures the NET for this IS-IS instance.

Step 7

exit

Example:

switch(config-router-vrf)# exit

switch(config-router)#

Exits router VRF configuration mode.

Step 8

interface ethernet slot/port

Example:

switch(config)# interface ethernet 1/2

switch(config-if)#

Enters interface configuration mode.

Step 9

vrf member vrf-name

Example:

switch(config-if)# vrf member RemoteOfficeVRF

Adds this interface to a VRF.

Step 10

ip address ip-prefix/length

Example:

switch(config-if)# ip address 192.0.2.1/16

Configures an IP address for this interface. You must do this step after you assign this interface to a VRF.

Step 11

ip router isis instance-tag

Example:

switch(config-if)# ip router isis Enterprise

Associates this IPv4 interface with an IS-IS instance.

Step 12

show isis [vrf vrf-name] [instance-tag] interface [interface-type slot/port]

Example:

switch(config-if)# show isis Enterprise ethernet 1/2

(Optional) Displays IS-IS information for an interface. in a VRF.

Step 13

copy running-config startup-config

Example:

switch(config-if)# copy running-config startup-config

(Optional) Saves this configuration change.

The following example shows how to create a VRF and add an interface to the VRF:

switch# configure terminal

switch(config)# vrf context NewVRF

switch(config-vrf)# exit

switch(config)# router isis Enterprise

switch(config-router)# vrf NewVRF

switch(config-router-vrf)# net 47.0004.004d.0001.0001.0c11.1111.00

switch(config-router-vrf)# interface ethernet 1/2

switch(config-if)# vrf member NewVRF

switch(config-if)# ip address 192.0.2.1/16

switch(config-if)# ip router isis Enterprise

switch(config-if)# copy running-config startup-config

Tuning IS-IS

You can tune IS-IS to match your network requirements.

You can use the following optional commands in router configuration mode to tune IS-IS:

Command

Purpose

lsp-gen-interval [level-1 | level-2] lsp-max-wait [lsp-initial-wait lsp-second-wait]

Example:

switch(config-router)# lsp-gen-interval level-1 500 500 500

Configures the IS-IS throttle for LSP generation. The optional parameters are as follows:

- lsp-max-wait—The maximum wait between the trigger and LSP generation. The range is from 500 to 65535 milliseconds.

- lsp-initial-wait—The initial wait between the trigger and LSP generation. The range is from 50 to 65535 milliseconds.

- lsp-second-wait—The second wait used for LSP throttle during backoff. The range is from 50 to 65535 milliseconds.

max-lsp-lifetime lifetime

Example:

switch(config-router)# max-lsp-lifetime 500

Sets the maximum LSP lifetime in seconds. The range is from 1 to 65535. The default is 1200.

metric-style transition

Example:

switch(config-router)# metric-style transition

Enables IS-IS to generate and accept both narrow metric-style Type Length Value (TLV) objects and wide metric-style TLV objects. The default is disabled.

spf-interval [level-1 | level-2] spf-max-wait [spf-initial-wait spf-second-wait]

Example:

switch(config-router)# spf-interval level-2 500 500 500

Configures the interval between LSA arrivals. The optional parameters are as follows:

- lsp-max-wait—The maximum wait between the trigger and SPF computation. The range is from 500 to 65535 milliseconds.

- lsp-initial-wait—The initial wait between the trigger and SPF computation. The range is from 50 to 65535 milliseconds.

- lsp-second-wait—The second wait used for SPF computation during backoff. The range is from 50 to 65535 milliseconds.

You can use the following optional command in router address configuration mode:

Command

Purpose

adjacency-check

Example:

switch(config-router-af)# adjacency-check

Performs an adjacency check to verify that an IS-IS instance forms an adjacency only with a remote IS-IS entity that supports the same address family. This command is enabled by default.

You can use the following optional commands in interface configuration mode to tune IS-IS:

Command

Purpose

isis csnp-interval seconds [level-1 | level-2]

Example:

switch(config-if)# isis csnp-interval 20

Sets the complete sequence number PDU (CNSP) interval in seconds for IS-IS. The range is from 1 to 65535. The default is 10.

isis hello-interval seconds [level-1 | level-2]

Example:

switch(config-if)# isis hello-interval 20

Sets the hello interval in seconds for IS-IS. The range is from 1 to 65535. The default is 10.

isis hello-multiplier num [level-1 | level-2]

Example:

switch(config-if)# isis hello-multiplier 20

Specifies the number of IS-IS hello packets that a neighbor must miss before the router tears down an adjacency. The range is from 3 to 1000. The default is 3.

isis lsp-interval milliseconds

Example:

switch(config-if)# isis lsp-interval 20

Sets the interval in milliseconds between LSPs sent on this interface during flooding. The range is from 10 to 65535. The default is 33.

Verifying the IS-IS Configuration

To display the IS-IS configuration, perform one of the following tasks:

Command

Purpose

show isis [instance-tag] adjacency [interface] [detail | summary] [vrf vrf-name]

Displays the IS-IS adjacencies. Use the clear isis adjacency command to clear these statistics.

show isis [instance-tag] database [level-1 | level-2] [detail | summary] [LSP ID] {[ip prefix ip-prefix] | | [router-id router-id] | [adjacency node-id] | [zero-sequence]} [vrf vrf-name]

Displays the IS-IS LSP database.

show isis [instance-tag] hostname [vrf vrf-name]

Displays the dynamic host exchange information.

show isis [instance-tag] interface [brief | interface] [level-1 | level-2] [vrf vrf-name]

Displays the IS-IS interface information.

show isis [instance-tag] mesh-group [mesh-id] [vrf vrf-name]

Displays the mesh group information.

show isis [instance-tag] protocol [vrf vrf-name]

Displays information about the IS-IS protocol.

show isis [instance-tag] ip | redistribute route [ip-address | summary] [[ip-prefix] [longer-prefixes [summary]] [vrf vrf-name]

Displays the IS-IS route redistribution information.

show isis [instance-tag] ip route [ip-address | summary] [ip-prefix [longer-prefixes [summary]] [detail] [vrf vrf-name]

Displays the IS-IS route table.

show isis [instance-tag] rrm [interface] [vrf vrf-name]

Displays the IS-IS interface retransmission information.

show isis [instance-tag] srm [interface] [vrf vrf-name]

Displays the IS-IS interface flooding information.

show isis [instance-tag] ssn [interface] [vrf vrf-name]

Displays the IS-IS interface PSNP information.

show isis [instance-tag] [ip summary-address [ip-address] | [ip-prefix] [vrf vrf-name]

Displays the IS-IS summary address information.

show running-configuration isis

Displays the current running IS-IS configuration.

show tech-support isis [detail]

Displays the technical support details for IS-IS.

For detailed information about the fields in the output from these commands, see the Cisco Nexus 7000 Series NX-OS Command Reference.

Monitoring IS-IS

To display IS-IS statistics, use the following commands:

Command

Purpose

show isis [instance-tag] adjacency [interface] [system-ID] [detail] [summary] [vrf vrf-name]

Displays the IS-IS adjacency statistics.

show isis [instance-tag] database [level-1 | level-2] [detail | summary] [lsip] {[adjacency id] ip prefix prefix] [router-id id] [zero-sequence]} [vrf vrf-name]

Displays the IS-IS database statistics.

show isis [instance-tag] statistics [interface] [vrf vrf-name]

Displays the IS-IS interface statistics.

show isis ip route-map statistics redistribute {bgp id | eigrp id | isis id | ospf id | rip id | static} [vrf vrf-name]

Displays the IS-IS redistribution statistics.

show isis route-map statistics distribute {level-1 | level-2} into {level-1 | level-2}} [vrf vrf-name]

Displays IS-IS distribution statistics for routes distributed between levels.

show isis [instance-tag] spf-log [detail] [vrf vrf-name]

Displays the IS-IS SPF calculation statistics.

show isis [instance-tag] traffic [interface] [vrf vrf-name]

Displays the IS-IS traffic statistics.

Command

Purpose

clear isis [instance-tag] adjacency [* | [interface] [system-id id]] [vrf vrf-name]

Clears the IS-IS adjacency statistics.

clear isis ip route-map statistics redistribute {bgp id | direct | eigrp id | isis id | ospf id | rip id | static} [vrf vrf-name]

Clears the IS-IS redistribution statistics

clear isis route-map statistics distribute {level-1 | level-2} into {level-1 | level-2} [vrf vrf-name]

Clears IS-IS distribution statistics for routes distributed between levels.

clear isis [instance-tag] statistics [* | interface] [vrf vrf-name]

Clears the IS-IS interface statistics.

clear isis [instance-tag] traffic [* | interface] [vrf vrf-name]

Clears the IS-IS traffic statistics.

Configuration Examples for IS-IS

Additional References

For additional information related to implementing IS-IS, see the following sections:

- Related Documents

- Standards

Related Documents

Related Topic

Document Title

IS-IS CLI commands

Cisco Nexus 7000 Series NX-OS Unicast Routing Command Reference, Release 5.x

VDCs and VRFs

Cisco Nexus 7000 Series NX-OS Virtual Device Context Configuration Guide, Release 5.x

Standards

Standards

Title

No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.

—

Feature History for IS-IS

Table 9-2 lists the release history for this feature.

Table 9-2 Feature History for IS-IS

Feature Name

Releases

Feature Information

BFD

5.0(2)

Added support for BFD. See the Cisco Nexus 7000 Series NX-OS Interfaces Configuration Guide, Release 5.x, for more information.

Graceful shutdown

4.2(1)

Added support to gracefully shut down an IS-IS instance or IS-IS on an interface but preserve the IS-IS configuration.

Limits on redistributed routes

4.2(1)

Added support for limiting the number of redistributed routes.

Transient mode for hello padding

4.1(2)

Added support to set or unset the hello padding mode.

Attached bit

4.1(2)

Added support to set or unset the attached bit.

IS-IS

4.0(1)

Managing the Unicast RIB and FIB

This chapter describes how to manage routes in the unicast Routing Information Base (RIB) and the Forwarding Information Base (FIB) on the Cisco NX-OS device.

This chapter includes the following sections:

- Information About the Unicast RIB and FIB

- Licensing Requirements for the Unicast RIB and FIB

- Guidelines and Limitations

- Default Settings

- Managing the Unicast RIB and FIB

- Verifying the Unicast RIB and FIB

- Additional References

- Feature History for Unicast RIB and FIB

Information About the Unicast RIB and FIB

The unicast RIB (IPv4 RIB and IPv6 RIB) and FIB are part of the Cisco NX-OS forwarding architecture, as shown in Figure 15-1.

Figure 15-1 Cisco NX-OS Forwarding Architecture

The unicast RIB exists on the active supervisor. It maintains the routing table with directly connected routes, static routes, and routes learned from dynamic unicast routing protocols. The unicast RIB also collects adjacency information from sources such as the Address Resolution Protocol (ARP). The unicast RIB determines the best next hop for a given route and populates the unicast forwarding information bases (FIBs) on the modules by using the services of the unicast FIB distribution module (FDM).

Each dynamic routing protocol must update the unicast RIB for any route that has timed out. The unicast RIB then deletes that route and recalculates the best next hop for that route (if an alternate path is available).

This section includes the following topics:

- Layer 3 Consistency Checker

- Dynamic TCAM Allocation

- Maximum TCAM Entries and FIB Scale Limits

- Virtualization Support

Layer 3 Consistency Checker

In rare instances, an inconsistency can occur between the unicast RIB and the FIB on each module. In Cisco NX-OS Release 4.0(3) and later releases, Cisco NX-OS supports the Layer 3 consistency checker. This feature detects inconsistencies between the unicast IPv4 RIB on the supervisor module and the FIB on each interface module. Inconsistencies include the following:

- Missing prefix

- Extra prefix

- Wrong next-hop address

- Incorrect Layer 2 rewrite string in the ARP or neighbor discovery (ND) cache

The Layer 3 consistency checker compares the FIB entries to the latest adjacency information from the Adjacency Manager (AM) and logs any inconsistencies. The consistency checker then compares the unicast RIB prefixes to the module FIB and logs any inconsistencies. See the “Triggering the Layer 3 Consistency Checker” section.

You can then manually clear any inconsistencies. See the “Clearing Forwarding Information in the FIB” section.

Dynamic TCAM Allocation

Dynamic TCAM allocation reallocates unused TCAM blocks on non-XL modules to an adjacent region when all existing blocks in that region are full. Dynamic TCAM allocation allows more flexibility in the number of routes that the FIB can allocate for a route type.

Cisco NX-OS divides the FIB to support multiple address families. The FIB TCAM for non-XL modules has 128K physical entries.

Table 15-1 describes the default FIB TCAM allocation.

Table 15-1 Default FIB TCAM Allocation

Region

Default # Routes

#TCAM blocks

Entry size

IPv4 unicast routes

56,000

7

72 bits

IPv4 multicast routes or

IPv6 unicast routes

32,000

8

144 bits

IPv6 multicast routes

2,000

1

288 bits

Maximum TCAM Entries and FIB Scale Limits

The FIB TCAM entries are system wide resources that are shared across virtual device contexts (VDC) configured on the module. Table 15-2 describes the supported maximum FIB scale entries on the Nexus 7000 system configuration per route-type.

Table 15-2 Maximum Supported TCAM Entries and FIB Scale Limits

Module Type in a VDC

Maximum TCAM Physical Entries in a VDC

Maximum Supported IPv4 Unicast Routes

Maximum Supported IPv4 Multicast Routes

Maximum Supported IPv6 Unicast Routes

Maximum Supported IPv6 Multicast Routes

Only non-XL modules in a VDC

128K

112,000

32,000 mroutes

56,000 routes

2000 routes

Only XL modules in a VDC

900K

900,000

32,000 mroutes

350,000 routes

2000 routes

Mix of XL/non-XL modules in same VDC

128K

112,000

32,000 mroutes

56,000 routes

2000 routes

Note Table 15-2 captures the scale limits in a VDC. In a Cisco Nexus 7000 system, the total memory on the supervisor module restricts the actual route scale limits across all VDCs in the system.

Note Do not exceed the maximum route limits for non-XL modules in a VDC that contains both XL modules and non-XL modules.

Note The actual FIB TCAM can scale to a higher scale number from a hardware perspective. Table 15-2 captures the currently supported FIB sizes.

Note The maximum routes are individual route-type maximum values and these values are not cumulative across each route-type.

You must install the Scalable Services License (see the Cisco NX-OS Licensing Guide) and configure the higher shared memory sizes (see the Cisco Nexus 7000 Series NX-OS Virtual Device Context Configuration Guide, Release 5.x) for the routing table to enable the higher FIB scale on the XL modules. See the Cisco Nexus 7000 Series Hardware Installation and Reference Guide for more information on the XL modules.

When you install the Scalable Services license, you may see the following system message:

"2011 Mar 30 12:38:13 switch %PLTFM_CONFIG-4-XL_LICENSE_MIX_NOTIFY: Mixed use of non-XL with XL modules in the same VDC may limit common resources to non-XL capacity."

This message occurs if you install the Scalable Services license in a system with non-XL modules or when non-XL modules come on line after you install this license.

Note The full IPv4 Internet route tables currently have more than 300K routes and require the XL modules.

Virtualization Support

The unicast RIB and FIB support virtual routing and forwarding (VRF) instances. VRF exists within VDCs. By default, Cisco NX-OS places you in the default VDC and default VRF unless you specifically configure another VDC and VRF. For more information, see the Cisco Cisco Nexus 7000 Series NX-OS Virtual Device Context Configuration Guide, Release 5.x and see Chapter14, “Configuring Layer 3 Virtualization”

Licensing Requirements for the Unicast RIB and FIB

The following table shows the licensing requirements for this feature:

Product

License Requirement

Cisco NX-OS

The unicast RIB and FIB require no license. Any feature not included in a license package is bundled with the Cisco NX-OS system images and is provided at no extra charge to you. For a complete explanation of the Cisco NX-OS licensing scheme, see the Cisco NX-OS Licensing Guide.

Guidelines and Limitations

Unicast RIB and FIB have the following configuration guidelines and limitations:

- You must install the Scalable Services license and configure the higher shared memory sizes to enable the higher FIB sizes for XL modules.

Default Settings

Table 15-3 lists the default settings for unicast RIB and FIB parameters.

Table 15-3 Default Unicast RIB and FIB Parameters

Parameters

Default

Dynamic TCAM allocation

Enabled by default and cannot be disabled

Managing the Unicast RIB and FIB

This section includes the following topics:

- Displaying Module FIB Information

- Configuring Load Sharing in the Unicast FIB

- Configuring Per-Packet Load Sharing

- Displaying Routing and Adjacency Information

- Triggering the Layer 3 Consistency Checker

- Clearing Forwarding Information in the FIB

- Configuring Maximum Routes for the Unicast RIB

- Estimating Memory Requirements for Routes

- Clearing Routes in the Unicast RIB

Note If you are familiar with the Cisco IOS CLI, be aware that the Cisco NX-OS commands for this feature might differ from the Cisco IOS commands that you would use.

Displaying Module FIB Information

You can display the FIB information on a module.

DETAILED STEPS

To display the FIB information on a module, use the following commands in any mode:

Command

Purpose

show ip fib adjacency module slot

Example:

switch# show ip fib adjacency module 2

Displays the adjacency information for IPv4.

show forwarding { ipv4 | ipv6 } adjacency module slot

Example:

switch# show forwarding ipv6 adjacency module 2

Displays the adjacency information for IPv4 or IPv6.

show ip fib interfaces module slot

Example:

switch# show ip fib interfaces module 2

Displays the FIB interface information for IPv4.

show ip fib route module slot

Example:

switch# show ip fib route module 2

Displays the route table for IPv4.

show forwarding { ipv4 | ipv6 } route module slot

Example:

switch# show forwarding ipv6 route module 2

Displays the route table for IPv4 or IPv6.

This example shows the FIB contents on a module:

switch# show ip fib route module 2

IPv4 routes for table default/base

------------------+------------------+---------------------

Prefix | Next-hop | Interface

------------------+------------------+---------------------

0.0.0.0/32 Drop Null0

255.255.255.255/32 Receive sup-eth1

Configuring Load Sharing in the Unicast FIB

Dynamic routing protocols such as Open Shortest Path First (OSPF) support load balancing with equal-cost multipath (ECMP). The routing protocol determines its best routes based on the metrics configured for the protocol and installs up to the protocol-configured maximum paths in the unicast RIB. The unicast RIB compares the administrative distances of all routing protocol paths in the RIB and selects a best path set from all of the path sets installed by the routing protocols. The unicast RIB installs this best path set into the FIB for use by the forwarding plane.

The forwarding plane uses a load-sharing algorithm to select one of the installed paths in the FIB to use for a given data packet.

You can globally configure the following load-sharing settings:

- Load-share mode—Selects the best path based on the destination address and port or the source and the destination address and port.

- Universal ID—Sets the random seed for the hash algorithm. You do not need to configure the Universal ID. Cisco NX-OS chooses the Universal ID if you do not configure it.

Note Load sharing uses the same path for all packets in a given flow. A flow is defined by the load-sharing method that you configure. For example, if you configure source-destination load sharing, then all packets with the same source IP address and destination IP address pair follow the same path.

To configure the unicast FIB load-sharing algorithm, use the following command in global configuration mode:

Command

Purpose

ip load-sharing address { destination port destination | source-destination [ port source-destination ]} [ universal-id seed ]

Example:

switch(config)# ip load-sharing address source-destination

Configures the unicast FIB load-sharing algorithm for data traffic. The universal-id range is from 1 to 4294967295.

To display the unicast FIB load-sharing algorithm, use the following command in any mode:

Command

Purpose

show ip load-sharing

Example:

switch(config)# show ip load-sharing address source-destination

Displays the unicast FIB load-sharing algorithm for data traffic.

To display the route that the unicast RIB and FIB use for a particular source address and destination address, use the following command in any mode:

Command

Purpose

show routing hash source-addr dest-addr [ source-port dest-port ] [ vrf vrf-name ]

Example:

switch# show routing hash 192.0.2.1 10.0.0.1

Displays the route that the unicast RIB FIB use for a source and destination address pair. The source address and destination address format is x.x.x.x. The source port and destination port range is from 1 to 65535. The VRF name can be any case-sensitive, alphanumeric string up to 64 characters.

This example shows the route selected for a source/destination pair:

switch# show routing hash 10.0.0.5 30.0.0.2

Load-share parameters used for software forwarding:

load-share mode: address source-destination port source-destination

Universal-id seed: 0xe05e2e85

Hash for VRF "default"

Hashing to path *20.0.0.2 (hash: 0x0e), for route:

Configuring Per-Packet Load Sharing

You can use per-packet load sharing to evenly distribute data traffic in an IP network over multiple equal-cost connections. Per-packet load sharing allows the router to send successive data packets over paths on a packet-by-packet basis rather than on a per-flow basis.

Note Using per-packet load sharing can result in out-of-order packets. Packets for a given pair of source-destination hosts might take different paths and arrive at the destination out of order. Make sure you understand the implications of out-of-order packets to your network and applications. Per-packet load sharing is not appropriate for all networks. Per-flow load sharing ensures packets always arrive in the order that they were sent.

Per-packet load sharing uses the round-robin method to determine which path each packet takes to the destination. With per-packet load sharing enabled on interfaces, the router sends one packet for destination1 over the first path, the second packet for (the same) destination1 over the second path, and so on. Per-packet load sharing ensures balancing over multiple links.

Use per-packet load sharing to ensure that a path for a single source-destination pair does not get overloaded. If most of the traffic passing through parallel links is for a single pair, per-destination load sharing will overload a single link while other links will have very little traffic. Enabling per-packet load sharing allows you to use alternate paths to the same busy destination.

Note Per-packet load sharing on an interface overrides the global load-sharing configuration.

You configure per-packet load sharing on the input interface. This configuration determines the output interface that Cisco NX-OS chooses for the packet.

For example, if you have ECMP paths on two output interfaces, Cisco NX-OS uses the following load-sharing methods for input packets on Ethernet 1/1:

- Per-packet load sharing if you configure per-packet load sharing on Ethernet 1/1.

- Per-flow load sharing.

The configurations for the other interfaces have no effect on the load-sharing method used for Ethernet 1/1 in this example.

To configure per-packet load sharing, use the following command in interface configuration mode:

Command

Purpose

ip load-sharing per-packet

Example:

switch(config-if)# ip load-sharing per-packet

Configures per-packet load sharing on an interface.

Displaying Routing and Adjacency Information

You can display the routing and adjacency information.

To display the routing and adjacency information, use the following commands in any mode:

Command

Purpose

show { ip | ipv6 } route [ route-type | interface int-type number | next-hop ]

Example:

switch# show ip route

Displays the unicast route table. The route-type argument can be a single route prefix, direct, static, or a dynamic route protocol. Use the ? command to see the supported interfaces.

show { ip | ipv6 } adjacency [ prefix | interface-type number [ summary ]| non-best ] [ detail ] [ vrf vrf-id ]

Example:

switch# show ip adjacency

Displays the adjacency table. The argument ranges are as follows:

- prefix —Any IPv4 or IPv6 prefix address.

- interface-type number —Use the ? command to see the supported interfaces.

- vrf-id —Any case-sensitive, alphanumeric string up to 64 characters.

show { ip | ipv6 } routing [ route-type | interface int-type number | next-hop | recursive-next-hop | summary | updated { since | until } time ]

Example:

switch# show routing summary

Displays the unicast route table. The route-type argument can be a single route prefix, direct, static, or a dynamic route protocol. Use the ? command to see the supported interfaces.

This example displays the unicast route table:

switch# show ip route

IP Route Table for Context "default"

'*' denotes best ucast next-hop '**' denotes best mcast next-hop

'[x/y]' denotes [preference/metric]

0.0.0.0/0, 1 ucast next-hops, 0 mcast next-hops

*via 10.1.1.1, mgmt0, [1/0], 5d21h, static

0.0.0.0/32, 1 ucast next-hops, 0 mcast next-hops

*via Null0, [220/0], 1w6d, local, discard

10.1.0.0/22, 1 ucast next-hops, 0 mcast next-hops, attached

*via 10.1.1.55, mgmt0, [0/0], 5d21h, direct

10.1.0.0/32, 1 ucast next-hops, 0 mcast next-hops, attached

*via 10.1.0.0, Null0, [0/0], 5d21h, local

10.1.1.1/32, 1 ucast next-hops, 0 mcast next-hops, attached

*via 10.1.1.1, mgmt0, [2/0], 5d16h, am

10.1.1.55/32, 1 ucast next-hops, 0 mcast next-hops, attached

*via 10.1.1.55, mgmt0, [0/0], 5d21h, local

10.1.1.253/32, 1 ucast next-hops, 0 mcast next-hops, attached

*via 10.1.1.253, mgmt0, [2/0], 5d20h, am

10.1.3.255/32, 1 ucast next-hops, 0 mcast next-hops, attached

*via 10.1.3.255, mgmt0, [0/0], 5d21h, local

255.255.255.255/32, 1 ucast next-hops, 0 mcast next-hops

*via Eth Inband Port, [0/0], 1w6d, local

This example shows the adjacency information:

switch# show ip adjacency

IP Adjacency Table for context default

Total number of entries: 2

Address Age MAC Address Pref Source Interface Best

10.1.1.1 02:20:54 00e0.b06a.71eb 50 arp mgmt0 Yes

10.1.1.253 00:06:27 0014.5e0b.81d1 50 arp mgmt0 Yes

Triggering the Layer 3 Consistency Checker

You can manually trigger the Layer 3 consistency checker.

To manually trigger the Layer 3 consistency checker, use the following commands in global configuration mode:

Command

Purpose

test forwarding [ ipv4 | ipv6 ] [ unicast] inconsistency [ vrf vrf-name ] [ module { slot | all }]

Example:

switch(config)# test forwarding inconsistency

Starts a Layer 3 consistency check. The vrf-name can be any case-sensitive, alphanumeric string up to 64 characters. The slot range is from 1 to 10.

To stop the Layer 3 consistency checker, use the following commands in global configuration mode:

Command

Purpose

test forwarding [ ipv4 | ipv6 ] [ unicast ] inconsistency [ vrf vrf-name ] [ module { slot | all }] stop

Example:

switch# test forwarding inconsistency stop

Stops a Layer 3 consistency check. The vrf-name can be any case-sensitive, alphanumeric string up to 64 characters. The slot range is from 1 to 10.

To display the Layer 3 inconsistencies, use the following commands in any mode:

Command

Purpose

show forwarding [ ipv4 | ipv6 ] inconsistency [ vrf vrf-name ] [ module { slot | all }]

Example:

switch# show forwarding inconsistency

Displays the results of a Layer 3 consistency check. The vrf-name can be any case-sensitive, alphanumeric string up to 64 characters. The slot range is from 1 to 10.

Clearing Forwarding Information in the FIB

You can clear one or more entries in the FIB. Clearing a FIB entry does not affect the unicast RIB.

Caution The clear forwarding command disrupts forwarding on the device.

To clear an entry in the FIB, including a Layer 3 inconsistency, use the following command in any mode:

Command

Purpose

clear forwarding { ipv4 | ipv6 } route {* | prefix } [ vrf vrf-name ] module { slot | all }

Example:

switch# clear forwarding ipv4 route * module 1

Clears one or more entries from the FIB. The route options are as follows:

- *—All routes.

- prefix —Any IP or IPv6 prefix.

The vrf-name can be any case-sensitive, alphanumeric string up to 64 characters. The slot range is from 1 to 10.

Configuring Maximum Routes for the Unicast RIB

You can configure the maximum number of routes allowed in the routing table.

BEFORE YOU BEGIN

Ensure that you are in the default VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. vrf context vrf-name

3. ipv4 unicast

4. maximum routes max-routes [threshold [reinstall threshold] | warning-only]

5. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters global configuration mode.

Step 2

vrf context vrf-name

Example:

switch(config)# vrf context Red

switch(config-vrf)#

Creates a VRF and enters VRF configuration mode.

Step 3

ipv4 unicast

Example:

switch(config-vrf)# ipv4 unicast

switch(config-vrf-af-ipv4)#

Enters address family configuration mode.

Step 4

maximum routes max-routes [ threshold [reinstall threshold ] | warning-only]

Example:

switch(config-vrf-af-ipv4)# maximum routes 250 90

Configures the maximum number of routes allowed in the routing table. The range is from 1 to 4294967295.

You can optionally specify the following:

- threshold —Percentage of maximum routes that triggers a warning message. The range is from 1 to 100.

- warning-only —Logs a warning message when the maximum number of routes is exceeded.

- reinstall threshold —Reinstalls routes that previously exceeded the maximum route limit and were rejected and specifies the threshold value at which to reinstall them. The threshold range is from 1 to 100.

Step 5

copy running-config startup-config

Example:

switch(config-vrf-af-ipv4)# copy running-config startup-config

(Optional) Saves this configuration change.

Estimating Memory Requirements for Routes

You can estimate the memory that a number of routes and next-hop addresses will use.

To estimate the memory requirements for routes, use the following command in any mode:

Command

Purpose

show routing {ipv6} memory estimate routes num-routes next-hops num-nexthops

Example:

switch# show routing memory estimate routes 5000 next-hops 2

Displays the memory requirements for routes. The num-routes range is from 1000 to 1000000. The num-nexthops range is from 1 to 16.

Clearing Routes in the Unicast RIB

You can clear one or more routes from the unicast RIB.

Caution The * keyword is severely disruptive to routing.

To clear one or more entries in the unicast RIB, use the following commands in any mode:

Command

Purpose

clear { ip | ipv4 | ipv6 } route {* | { route | prefix/length }[ next-hop interface ]} [ vrf vrf-name ]

Example:

switch(config)# clear ip route 10.2.2.2

Clears one or more routes from both the unicast RIB and all the module FIBs. The route options are as follows:

- *—All routes.

- route —An individual IP or IPv6 route.

- prefix/length —Any IP or IPv6 prefix.

- next-hop —The next-hop address

- interface —The interface to reach the next-hop address.

The vrf-name can be any case-sensitive, alphanumeric string up to 64 characters.

clear routing [ multicast | unicast ] [ ip | ipv4 | ipv6 ] {* | { route | prefix/length }[ next-hop interface ]} [ vrf vrf-name ]

Example:

switch(config)# clear routing ip 10.2.2.2

Clears one or more routes from the unicast RIB. The route options are as follows:

- *—All routes.

- route —An individual IP or IPv6 route.

- prefix/length —Any IP or IPv6 prefix.

- next-hop —The next-hop address

- interface —The interface to reach the next-hop address.

The vrf-name can be any case-sensitive, alphanumeric string up to 64 characters.

Verifying the Unicast RIB and FIB

To display the unicast RIB and FIB information, perform one the following tasks:

Command

Purpose

show forwarding adjacency

Displays the adjacency table on a module.

show forwarding distribution {clients | fib-state}

Displays the FIB distribution information.

show forwarding interfaces module slot

Displays the FIB information for a module.

show forwarding {ip | ipv4 | ipv6} route

Displays routes in the FIB.

show {ip | ipv6} adjacency

Displays the adjacency table.

show {ip | ipv6} route

Displays IPv4 or IPv6 routes from the unicast RIB.

show routing

Displays routes from the unicast RIB.

Additional References

For additional information related to managing unicast RIB and FIB, see the following sections:

- Related Documents

- Feature History for Unicast RIB and FIB

Related Documents

Related Topic

Document Title

Unicast RIB and FIB CLI commands

Cisco Nexus 7000 Series NX-OS Unicast Routing Command Reference, Release 5.x

Feature History for Unicast RIB and FIB

Table 15-4 lists the release history for this feature.

Table 15-4 Feature History for Unicast RIB and FIB

Feature Name

Releases

Feature Information

Maximum routes

5.2(1)

Added support to configure the maximum number of routes allowed in the routing table.

TCAM Size for XL Modules

5.0(2)

Added support for larger TCAM and FIB sizes with XL modules.

Dynamic TCAM allocation

5.0(2)

Enabled by default and cannot be disabled.

IPv6 forwarding inconsistency checker

4.2(1)

Added support to check for inconsistencies in the IPv6 forwarding table.

Dynamic TCAM allocation

4.2(1)

Added support for dynamically allocating TCAM blocks in the FIB.

Per-packet load sharing

4.1(2)

Added support to load balance per packet on an interface.

Unicast RIB and FIB

4.0(3)

Added support to clear individual routes in unicast RIB and FIB.

Unicast RIB and FIB

4.0(1)

This feature was introduced.

Configuring Object Tracking

This chapter describes how to configure object tracking on the Cisco NX-OS device.

This chapter includes the following sections:

- Information About Object Tracking

- Licensing Requirements for Object Tracking

- Prerequisites for Object Tracking

- Guidelines and Limitations

- Default Settings

- Configuring Object Tracking

- Verifying the Object Tracking Configuration

- Configuration Examples for Object Tracking

- Related Topics

- Additional References

- Feature History for Object Tracking

Information About Object Tracking

Object tracking allows you to track specific objects on the device, such as the interface line protocol state, IP routing, and route reachability, and to take action when the tracked object’s state changes. This feature allows you to increase the availability of the network and shorten recovery time if an object state goes down.

This section includes the following topics:

- Object Tracking Overview

- Object Track List

- High Availability

- Virtualization Support

Object Tracking Overview

The object tracking feature allows you to create a tracked object that multiple clients can use to modify the client behavior when a tracked object changes. Several clients register their interest with the tracking process, track the same object, and take different actions when the object state changes.

Clients include the following features:

- Embedded Event Manager (EEM)

- Gateway Load Balancing Protocol (GLBP)

- Hot Standby Redundancy Protocol (HSRP)

- Virtual port channel (vPC)

- Virtual Router Redundancy Protocol (VRRP)

The object tracking monitors the status of the tracked objects and communicates any changes made to interested clients. Each tracked object is identified by a unique number that clients can use to configure the action to take when a tracked object changes state.

Cisco NX-OS tracks the following object types:

- Interface line protocol state—Tracks whether the line protocol state is up or down.

- Interface IP routing state—Tracks whether the interface has an IPv4 or IPv6 address and if IPv4 or IPv6 routing is enabled and active.

- IP route reachability—Tracks whether an IPv4 or IPv6 route exists and is reachable from the local device.

For example, you can configure HSRP to track the line protocol of the interface that connects one of the redundant routers to the rest of the network. If that link protocol goes down, you can modify the priority of the affected HSRP router and cause a switchover to a backup router that has better network connectivity.

Object Track List

An object track list allows you to track the combined states of multiple objects. Object track lists support the following capabilities:

- Boolean "and" function—Each object defined within the track list must be in an up state so that the track list object can become up.

- Boolean "or" function—At least one object defined within the track list must be in an up state so that the tracked object can become up.

- Threshold percentage—The percentage of up objects in the tracked list must be greater than the configured up threshold for the tracked list to be in the up state. If the percentage of down objects in the tracked list is above the configured track list down threshold, the tracked list is marked as down.

- Threshold weight—Assign a weight value to each object in the tracked list, and a weight threshold for the track list. If the combined weights of all up objects exceeds the track list weight up threshold, the track list is in an up state. If the combined weights of all the down objects exceeds the track list weight down threshold, the track list is in the down state.

Other entities, such as virtual Port Channels (vPCs) can use an object track list to modify the state of a vPC based on the state of the multiple peer links that create the vPC. See the Cisco Nexus 7000 Series NX-OS Interfaces Configuration Guide, Release 5.x, for more information on vPCs.

See the “Configuring an Object Track List with a Boolean Expression” section for more information on track lists.

High Availability

Object tracking supports high availability through stateful restarts. A stateful restart occurs when the object tracking process crashes. Object tracking also supports a stateful switchover on a dual supervisor system. Cisco NX-OS applies the runtime configuration after the switchover.

You can also use object tracking to modify the behavior of a client to improve overall network availability.

Virtualization Support

Object tracking supports Virtual Routing and Forwarding (VRF) instances. VRFs exist within virtual device contexts (VDCs). By default, Cisco NX-OS places you in the default VDC and default VRF unless you specifically configure another VDC and VRF. By default, Cisco NX-OS tracks the route reachability state of objects in the default VRF. If you want to track objects in another VRF, you must configure the object to be a member of that VRF (see the “Configuring Object Tracking for a Nondefault VRF” section).

For more information, see the Cisco Nexus 7000 Series NX-OS Virtual Device Context Configuration Guide, Release 5.x, and see Chapter14, “Configuring Layer 3 Virtualization”

Licensing Requirements for Object Tracking

The following table shows the licensing requirements for this feature:

Product

License Requirement

Cisco NX-OS

Object tracking requires no license. Any feature not included in a license package is bundled with the Cisco NX-OS system images and is provided at no extra charge to you. For a complete explanation of the Cisco NX-OS licensing scheme, see the Cisco NX-OS Licensing Guide.

Prerequisites for Object Tracking

Object tracking has the following prerequisites:

Note For a full list of feature-specific prerequisites, see the platform-specific documentation.

- If you configure VDCs, install the Advanced Services license and enter the desired VDC (see the Cisco Nexus 7000 Series NX-OS Virtual Device Context Configuration Guide, Release 5.x).

Guidelines and Limitations

Object tracking has the following configuration guidelines and limitations:

- Supports up to 500 tracked objects per VDC.

- Supports Ethernet, subinterfaces, tunnels, port channels, loopback interfaces, and VLAN interfaces.

- Supports one tracked object per HSRP group or GLBP group.

Default Settings

Table 21-1 lists the default settings for object tracking parameters.

Table 21-1 Default Object Tracking Parameters

Parameters

Default

Tracked Object VRF

Member of default VRF

Configuring Object Tracking

This section includes the following topics:

- Configuring Object Tracking for an Interface

- Deleting a Tracking Object

- Configuring Object Tracking for Route Reachability

- Configuring an Object Track List with a Boolean Expression

- Configuring an Object Track List with a Percentage Threshold

- Configuring an Object Track List with a Weight Threshold

- Configuring an Object Tracking Delay

- Configuring Object Tracking for a Nondefault VRF

Note If you are familiar with the Cisco IOS CLI, be aware that the Cisco NX-OS commands for this feature might differ from the Cisco IOS commands that you would use.

Configuring Object Tracking for an Interface

You can configure Cisco NX-OS to track the line protocol or IPv4 or IPv6 routing state of an interface.

BEFORE YOU BEGIN

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. track object-id interface interface-type number {{ip | ipv6} routing | line-protocol}

3. (Optional) show track [object-id]

4. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

track object-id interface interface-type number {{ip | ipv6} routing | line-protocol}

Example:

switch(config)# track 1 interface ethernet 1/2 line-protocol

switch(config-track)#

Creates a tracked object for an interface and enters tracking configuration mode. The object-id range is from 1 to 500.

Step 3

show track [object-id]

Example:

switch(config-track)# show track 1

(Optional) Displays object tracking information.

Step 4

copy running-config startup-config

Example:

switch(config-track)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to configure object tracking for the line protocol state on Ethernet 1/2:

switch# configure terminal

switch(config)# track 1 interface ethernet 1/2 line-protocol

switch(config-track)# copy running-config startup-config

This example shows how to configure object tracking for the IPv4 routing state on Ethernet 1/2:

switch# configure terminal

switch(config)# track 2 interface ethernet 1/2 ip routing

switch(config-track)# copy running-config startup-config

This example shows how to configure object tracking for the IPv6 routing state on Ethernet 1/2:

switch# configure terminal

switch(config)# track 3 interface ethernet 1/2 ipv6 routing

switch(config-track)# copy running-config startup-config

Deleting a Tracking Object

You can delete a object tracking.

BEFORE YOU BEGIN

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. no track object-id

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

no track object-id

Example:

switch(config)# no track 1 switch(config-track)#

Deletes a tracked object for an interface. The object-id range is from 1 to 500.

This example shows how to delete a object tracking:

switch# configure terminal

switch(config)# no track 1

switch(config-track)# copy running-config startup-config

Configuring Object Tracking for Route Reachability

You can configure Cisco NX-OS to track the existence and reachability of an IP route or IPv6 route.

BEFORE YOU BEGIN

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. track object-id {ip | ipv6} route prefix/length reachability

3. (Optional) show track [object-id]

4. (Optional) copy running-config startup-config

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

track object-id {ip | ipv6} route prefix/length reachability

Example:

Switch(config)# track 3 ipv6 route 2::5/64 reachability

switch(config-track)#

Creates a tracked object for a route and enters tracking configuration mode. The object-id range is from 1 to 500. The prefix format for IP is A.B.C.D/length, where the length range is from 1 to 32. The prefix format for IPv6 is A:B::C:D/length, where the length range is from 1 to 128.

Step 3

show track [object-id]

Example:

switch(config-track)# show track 1

(Optional) Displays object tracking information.

Step 4

copy running-config startup-config

Example:

switch(config-track)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to configure object tracking for an IPv4 route in the default VRF.

switch# configure terminal

switch(config)# track 4 ip route 192.0.2.0/8 reachability

switch(config-track)# copy running-config startup-config

This example shows how to configure object tracking for an IPv6 route in the default VRF.

switch# configure terminal

switch(config)# track 5 ipv6 route 10::10/128 reachability

switch(config-track)# copy running-config startup-config

Configuring an Object Track List with a Boolean Expression

You can configure an object track list that contains multiple tracked objects. A tracked list contains one or more objects. The Boolean expression enables two types of calculation by using either "and" or "or" operators. For example, when tracking two interfaces using the "and" operator, up means that both interfaces are up, and down means that either interface is down.

BEFORE YOU BEGIN

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. track track-number list boolean {and | or}

3. object object-number [not]

4. (Optional) show track

5. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

track track-number list boolean {and | or}

Example:

switch(config)# track 1 list boolean and

switch(config-track)#

Configures a tracked list object and enters tracking configuration mode. Specifies that the state of the tracked list is based on a Boolean calculation. The keywords are as follows:

- and —Specifies that the list is up if all objects are up or down if one or more objects are down. For example, when tracking two interfaces, up means that both interfaces are up, and down means that either interface is down.

- or —Specifies that the list is up if at least one object is up. For example, when tracking two interfaces, up means that either interface is up, and down means that both interfaces are down.

The track-number range is from 1 to 500.

Step 3

object object-id [not]

Example:

switch(config-track)# object 10

Adds a tracked object to the track list. The object-id range is from 1 to 500. The not keyword optionally negates the tracked object state.

Note The example means that when object 10 is up, the tracked list detects object 10 as down.

Step 4

show track

Example:

switch(config-track)# show track

(Optional) Displays object tracking information.

Step 5

copy running-config startup-config

Example:

switch(config-track)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to configure a track list with multiple objects as a Boolean “and”:

switch# configure terminal

switch(config)# track 1 list boolean and

switch(config-track)# object 10

switch(config-track)# object 20 not

Configuring an Object Track List with a Percentage Threshold

You can configure an object track list that contains a percentage threshold. A tracked list contains one or more objects. The percentage of up objects must exceed the configured track list up percent threshold before the track list is in an up state. For example, if the tracked list has three objects, and you configure an up threshold of 60 percent, two of the objects must be in the up state (66 percent of all objects) for the track list to be in the up state.

BEFORE YOU BEGIN

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. track track-number list threshold percentage

3. threshold percentage up up-value down down-value

4. object object-number

5. (Optional) show track

6. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

track track-number list threshold percentage

Example:

switch(config)# track 1 list threshold percentage

switch(config-track)#

Configures a tracked list object and enters tracking configuration mode. Specifies that the state of the tracked list is based on a configured threshold percent.

The track-number range is from 1 to 500.

Step 3

threshold percentage up up-value down down-value

Example:

switch(config-track)# threshold percentage up 70 down 30

Configures the threshold percent for the tracked list. The range from 0 to 100 percent.

Step 4

object object-id

Example:

switch(config-track)# object 10

Adds a tracked object to the track list. The object-id range is from 1 to 500.

Step 5

show track

Example:

switch(config-track)# show track

(Optional) Displays object tracking information.

Step 6

copy running-config startup-config

Example:

switch(config-track)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to configure a track list with an up threshold of 70 percent and a down threshold of 30 percent:

switch# configure terminal

switch(config)# track 1 list threshold percentage

switch(config-track)# threshold percentage up 70 down 30

switch(config-track)# object 10

switch(config-track)# object 20

switch(config-track)# object 30

Configuring an Object Track List with a Weight Threshold

You can configure an object track list that contains a weight threshold. A tracked list contains one or more objects. The combined weight of up objects must exceed the configured track list up weight threshold before the track list is in an up state. For example, if the tracked list has three objects with the default weight of 10 each, and you configure an up threshold of 15, two of the objects must be in the up state (combined weight of 20) for the track list to be in the up state.

BEFORE YOU BEGIN

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. track track-number list threshold weight

3. threshold weight up up-value down down-value

4. object object-id weight value

5. (Optional) show track

6. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

track track-number list threshold weight

Example:

switch(config)# track 1 list threshold weight

switch(config-track)#

Configures a tracked list object and enters tracking configuration mode. Specifies that the state of the tracked list is based on a configured threshold weight.

The track-number range is from 1 to 500.

Step 3

threshold weight up up-value down down-value

Example:

switch(config-track)# threshold weight up 30 down 10

Configures the threshold weight for the tracked list. The range from 1 to 255.

Step 4

object object-id weight value

Example:

switch(config-track)# object 10 weight 15

Adds a tracked object to the track list. The object-id range is from 1 to 500. The value range is from 1 to 255. The default weight value is 10.

Step 5

show track

Example:

switch(config-track)# show track

(Optional) Displays object tracking information.

Step 6

copy running-config startup-config

Example:

switch(config-track)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to configure a track list with an up weight threshold of 30 and a down threshold of 10:

switch# configure terminal

switch(config)# track 1 list threshold weight

switch(config-track)# threshold weight up 30 down 10

switch(config-track)# object 10 weight 15

switch(config-track)# object 20 weight 15

switch(config-track)# object 30

In this example, the track list is up if object 10 and object 20 are up, and the track list goes to the down state if all three objects are down.

Configuring an Object Tracking Delay

You can configure a delay for a tracked object or an object track list that delays when the object or list triggers a stage change. The tracked object or track list starts the delay timer when a state change occurs but does not recognize a state change until the delay timer expires. At that point, Cisco NX-OS checks the object state again and records a state change only if the object or list currently has a changed state. Object tracking ignores any intermediate state changes before the delay timer expires.

For example, for an interface line-protocol tracked object that is in the up state with a 20 second down delay, the delay timer starts when the line protocol goes down. The object is not in the down state unless the line protocol is down 20 seconds later.

You can configure independent up delay and down delay for a tracked object or track list. When you delete the delay, object tracking deletes both the up and down delay.

You can change the delay at any point. If the object or list is already counting down the delay timer from a triggered event, the new delay is computed as the following:

- If the new configuration value is less than the old configuration value, the timer starts with the new value.

- If the new configuration value is more than the old configuration value, the timer is calculated as the new configuration value minus the current timer countdown minus the old configuration value.

BEFORE YOU BEGIN

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. track object-id {parameters}

3. track track-number list {parameters}

4. delay {up up-time [down down-time] | down down-time [up up-time]}

5. (Optional) show track

6. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

track object-id {parameters}

Example:

switch(config)# track 2 ip route 192.0.2.0/8 reachability

switch(config-track)#

Creates a tracked object for a route and enters tracking configuration mode. The object-id range is from 1 to 500. The prefix format for IP is A.B.C.D/length, where the length range is from 1 to 32. The prefix format for IPv6 is A:B::C:D/length, where the length range is from 1 to 128.

Step 3

track track-number list {parameters}

Example:

switch(config)# track 1 list threshold weight

switch(config-track)#

Configures a tracked list object and enters tracking configuration mode. Specifies that the state of the tracked list is based on a configured threshold weight.

The track-number range is from 1 to 500.

Step 4

delay {up up-time [down down-time] | down down-time [up up-time]}

Example:

switch(config-track)# delay up 20 down 30

Configures the object delay timers. The range is from 0 to 180 seconds.

Step 5

show track

Example:

switch(config-track)# show track 3

(Optional) Displays object tracking information.

Step 6

copy running-config startup-config

Example:

switch(config-track)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to configure object tracking for a route and use delay timers:

switch# configure terminal

switch(config)# track 2 ip route 209.165.201.0/8 reachability

switch(config-track)# delay up 20 down 30

switch(config-track)# copy running-config startup-config

This example shows how to configure a track list with an up weight threshold of 30 and a down threshold of 10 with delay timers:

switch# configure terminal

switch(config)# track 1 list threshold weight

switch(config-track)# threshold weight up 30 down 10

switch(config-track)# object 10 weight 15

switch(config-track)# object 20 weight 15

switch(config-track)# object 30

switch(config-track)# delay up 20 down 30

This example shows the delay timer in the show track command output before and after an interface is shut down:

switch(config-track)# show track

Track 1

Interface loopback1 Line Protocol

Line Protocol is UP

1 changes, last change 00:00:13

Delay down 10 secs

qadc3-fhrp-ind45(config-track)# interface loopback 1

qadc3-fhrp-ind45(config-if)# shutdown

qadc3-fhrp-ind45(config-if)# show track

Track 1

Interface loopback1 Line Protocol

Line Protocol is delayed DOWN (8 secs remaining)<------- delay timer counting down

1 changes, last change 00:00:22

Delay down 10 secs

Configuring Object Tracking for a Nondefault VRF

You can configure Cisco NX-OS to track an object in a specific VRF.

BEFORE YOU BEGIN

Ensure that you are in the correct VDC (or use the switchto vdc command).

Ensure that nondefault VRFs are created first.

SUMMARY STEPS

1. configure terminal

2. track object-id {ip | ipv6} route prefix/length reachability

3. vrf member vrf-name

4. (Optional) show track [object-id]

5. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

track object-id {ip | ipv6} route prefix/length reachability

Example:

Switch# conf t

Switch(config)# track 3 ipv6 route 1::2/64 reachability

Switch(config-track)#

Creates a tracked object for a route and enters tracking configuration mode. The object-id range is from 1 to 500. The prefix format for IP is A.B.C.D/length, where the length range is from 1 to 32. The prefix format for IPv6 is A:B::C:D/length, where the length range is from 1 to 128.

Step 3

vrf member vrf-name

Example:

switch(config-track)# vrf member Red

Configures the VRF to use for tracking the configured object.

Step 4

show track [object-id]

Example:

switch(config-track)# show track 3

(Optional) Displays object tracking information.

Step 5

copy running-config startup-config

Example:

switch(config-track)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to configure object tracking for a route and use VRF Red to look up reachability information for this object:

switch# configure terminal

switch(config)# track 2 ip route 209.165.201.0/8 reachability

switch(config-track)# vrf member Red

switch(config-track)# copy running-config startup-config

This example shows how to configure object tracking for an IPv6 route and use VRF Red to look up reachability information for this object:

Switch# configure terminal

Switch(config)# track 3 ipv6 route 1::2/64 reachability

Switch(config-track)# vrf member Red

Switch(config-track)# copy running-config startup-config

This example shows how to modify tracked object 2 to use VRF Blue instead of VRF Red to look up reachability information for this object:

switch# configure terminal

switch(config)# track 2

switch(config-track)# vrf member Blue

switch(config-track)# copy running-config startup-config

Verifying the Object Tracking Configuration

To display object tracking configuration information, perform one the following tasks:

Command

Purpose

show track [object-id] [brief]

Displays the object tracking information for one or more objects.

show track [object-id] interface [brief]

Displays the interface-based object tracking information.

show track [object-id] {ip | ipv6} route [brief]

Displays the IPv4 or IPv6 route-based object tracking information.

show trun track

Displays the IP route IPv6 object tracking configuration information.

Configuration Examples for Object Tracking

This example shows how to configure object tracking for route reachability and use VRF Red to look up reachability information for this route:

switch# configure terminal

switch(config)# track 2 ip route 209.165.201.0/8 reachability

switch(config-track)# vrf member Red

switch(config-track)# copy running-config startup-config

Related Topics

See the following topics for information related to object tracking:

- Chapter 14, “Configuring Layer 3 Virtualization”

- Chapter 18, “Configuring GLBP”

- Chapter 19, “Configuring HSRP”

Additional References

For additional information related to implementing object tracking, see the following sections:

- Related Documents

- Standards

Related Documents

Related Topic

Document Title

Object Tracking CLI commands

Cisco Nexus 7000 Series NX-OS Unicast Routing Command Reference, Release 5.x

Configuring the Embedded Event Manager

Cisco Nexus 7000 Series NX-OS System Management Configuration Guide, Release 5.x

Standards

Standards

Title

No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.

—

Feature History for Object Tracking

Table 21-2 lists the release history for this feature.

Table 21-2 Feature History for Object Tracking

Feature Name

Releases

Feature Information

IPv6 support

5.0(2)

Added support for IPv6.

Tracking delay

4.2(4)

Added support for delaying a tracked object update.

Object track list

4.2(1)

Added support for object track lists and Boolean expressions.

Object tracking

4.0(1)

This feature was introduced.

Configuring OSPFv3

This chapter describes how to configure Open Shortest Path First version 3(OSPFv3) for IPv6 networks on the Cisco NX-OS device.

This chapter includes the following sections:

- Information About OSPFv3

- Licensing Requirements for OSPFv3

- Prerequisites for OSPFv3

- Guidelines and Limitations for OSPFv3

- Default Settings

- Configuring Basic OSPFv3

- Configuring Advanced OSPFv3

- Verifying the OSPFv3 Configuration

- Monitoring OSPFv3

- Configuration Examples for OSPFv3

- Related Topics

- Additional References

- Feature History for OSPFv3

Information About OSPFv3

OSPFv3 is an IETF link-state protocol (see “Overview” section). An OSPFv3 router sends a special message, called a hello packet, out each OSPF-enabled interface to discover other OSPFv3 neighbor routers. Once a neighbor is discovered, the two routers compare information in the Hello packet to determine if the routers have compatible configurations. The neighbor routers attempt to establish adjacency, which means that the routers synchronize their link-state databases to ensure that they have identical OSPFv3 routing information. Adjacent routers share link-state advertisements (LSAs) that include information about the operational state of each link, the cost of the link, and any other neighbor information. The routers then flood these received LSAs out every OSPF-enabled interface so that all OSPFv3 routers eventually have identical link-state databases. When all OSPFv3 routers have identical link-state databases, the network is converged (see the “Convergence” section). Each router then uses Dijkstra’s Shortest Path First (SPF) algorithm to build its route table.

You can divide OSPFv3 networks into areas. Routers send most LSAs only within one area, which reduces the CPU and memory requirements for an OSPF-enabled router.

OSPFv3 supports IPv6. For information about OSPF for IPv4, see Chapter 6, “Configuring OSPFv2”.

This section includes the following topics:

- Comparison of OSPFv3 and OSPFv2

- Hello Packet

- Neighbors

- Adjacency

- Designated Routers

- Areas

- Link-State Advertisement

- OSPFv3 and the IPv6 Unicast RIB

- Address Family Support

- Advanced Features

Comparison of OSPFv3 and OSPFv2

Much of the OSPFv3 protocol is the same as in OSPFv2. OSPFv3 is described in RFC 2740.

The key differences between the OSPFv3 and OSPFv2 protocols are as follows:

- OSPFv3 expands on OSPFv2 to provide support for IPv6 routing prefixes and the larger size of IPv6 addresses.

- LSAs in OSPFv3 are expressed as prefix and prefix length instead of address and mask.

- The router ID and area ID are 32-bit numbers with no relationship to IPv6 addresses.

- OSPFv3 uses link-local IPv6 addresses for neighbor discovery and other features.

- OSPFv3 can use the IPv6 authentication trailer (RFC 6506) or IPSec (RFC 4552) for authentication. However, neither of these options is supported on Cisco NX-OS.

- OSPFv3 redefines LSA types.

Hello Packet

OSPFv3 routers periodically send Hello packets on every OSPF-enabled interface. The hello interval determines how frequently the router sends these Hello packets and is configured per interface. OSPFv3 uses Hello packets for the following tasks:

- Neighbor discovery

- Keepalives

- Bidirectional communications

- Designated router election (see the “Designated Routers” section)

The Hello packet contains information about the originating OSPFv3 interface and router, including the assigned OSPFv3 cost of the link, the hello interval, and optional capabilities of the originating router. An OSPFv3 interface that receives these Hello packets determines if the settings are compatible with the receiving interface settings. Compatible interfaces are considered neighbors and are added to the neighbor table (see the “Neighbors” section).

Hello packets also include a list of router IDs for the routers that the originating interface has communicated with. If the receiving interface sees its own router ID in this list, then bidirectional communication has been established between the two interfaces.

OSPFv3 uses Hello packets as a keepalive message to determine if a neighbor is still communicating. If a router does not receive a Hello packet by the configureddead interval (usually a multiple of the hello interval), then the neighbor is removed from the local neighbor table.

Neighbors

An OSPFv3 interface must have a compatible configuration with a remote interface before the two can be considered neighbors. The two OSPFv3 interfaces must match the following criteria:

- Hello interval

- Dead interval

- Area ID (see the “Areas” section)

- Optional capabilities

If there is a match, the information is entered into the neighbor table:

- Neighbor ID—The router ID of the neighbor router.

- Priority—Priority of the neighbor router. The priority is used for designated router election (see the “Designated Routers” section).

- State—Indication of whether the neighbor has just been heard from, is in the process of setting up bidirectional communications, is sharing the link-state information, or has achieved full adjacency.

- Dead time—Indication of how long since the last Hello packet was received from this neighbor.

- Link-local IPv6 Address—The link-local IPv6 address of the neighbor.

- Designated Router—Indication of whether the neighbor has been declared the designated router or backup designated router (see the “Designated Routers” section).

- Local interface—The local interface that received the Hello packet for this neighbor.

When the first Hello packet is received from a new neighbor, the neighbor is entered into the neighbor table in the initialization state. Once bidirectional communication is established, the neighbor state becomes two-way. ExStart and exchange states come next, as the two interfaces exchange their link-state database. Once this is all complete, the neighbor moves into the full state, which signifies full adjacency. If the neighbor fails to send any Hello packets in the dead interval, then the neighbor is moved to the down state and is no longer considered adjacent.

Adjacency

Not all neighbors establish adjacency. Depending on the network type and designated router establishment, some neighbors become fully adjacent and share LSAs with all their neighbors, while other neighbors do not. For more information, see the “Designated Routers” section.

Adjacency is established using Database Description packets, Link State Request packets, and Link State Update packets in OSPFv3. The Database Description packet includes the LSA headers from the link-state database of the neighbor (see the “Link-State Database” section). The local router compares these headers with its own link-state database and determines which LSAs are new or updated. The local router sends a Link State Request packet for each LSA that it needs new or updated information on. The neighbor responds with a Link State Update packet. This exchange continues until both routers have the same link-state information.

Designated Routers

Networks with multiple routers present a unique situation for OSPFv3. If every router floods the network with LSAs, the same link-state information is sent from multiple sources. Depending on the type of network, OSPFv3 might use a single router, the designated router (DR), to control the LSA floods and represent the network to the rest of the OSPFv3 area (see the “Areas” section). If the DR fails, OSPFv3 selects a backup designated router (BDR). If the DR fails, OSPFv3 uses the BDR.

Network types are as follows:

- Point-to-point—A network that exists only between two routers. All neighbors on a point-to-point network establish adjacency and there is no DR.

- Broadcast—A network with multiple routers that can communicate over a shared medium that allows broadcast traffic, such as Ethernet. OSPFv3 routers establish a DR and BDR that controls LSA flooding on the network. OSPFv3 uses the well-known IPv6 multicast addresses, FF02::5, and a MAC address of 0100.5300.0005 to communicate with neighbors.

The DR and BDR are selected based on the information in the Hello packet. When an interface sends a Hello packet, it sets the priority field and the DR and BDR field if it knows who the DR and BDR are. The routers follow an election procedure based on which routers declare themselves in the DR and BDR fields and the priority field in the Hello packet. As a final determinant, OSPFv3 chooses the highest router IDs as the DR and BDR.

All other routers establish adjacency with the DR and the BDR and use the IPv6 multicast address FF02::6 to send LSA updates to the DR and BDR. Figure 7-1 shows this adjacency relationship between all routers and the DR.

DRs are based on a router interface. A router might be the DR for one network and not for another network on a different interface.

Figure 7-1 DR in Multi-Access Network

Areas

You can limit the CPU and memory requirements that OSPFv3 puts on the routers by dividing an OSPFv3 network into area s . An area is a logical division of routers and links within an OSPFv3 domain that creates separate subdomains. LSA flooding is contained within an area, and the link-state database is limited to links within the area. You can assign an area ID to the interfaces within the defined area. The Area ID is a 32-bit value that can be expressed as a number or in dotted decimal notation, such as 10.2.3.1.

Cisco NX-OS always displays the area in dotted decimal notation.

If you define more than one area in an OSPFv3 network, you must also define the backbone area, which has the reserved area ID of 0. If you have more than one area, then one or more routers become area border routers (ABRs). An ABR connects to both the backbone area and at least one other defined area (see Figure 7-2).

Figure 7-2 OSPFv3 Areas

The ABR has a separate link-state database for each area which it connects to. The ABR sends Inter-Area Prefix (type 3) LSAs (see the “Route Summarization” section) from one connected area to the backbone area. The backbone area sends summarized information about one area to another area. In Figure 7-2, Area 0 sends summarized information about Area 5 to Area 3.

OSPFv3 defines one other router type: the autonomous system boundary router (ASBR). This router connects an OSPFv3 area to another autonomous system. An autonomous system is a network controlled by a single technical administration entity. OSPFv3 can redistribute its routing information into another autonomous system or receive redistributed routes from another autonomous system. For more information, see the “Advanced Features” section.

Link-State Advertisement

OSPFv3 uses link-state advertisements (LSAs) to build its routing table.

This section includes the following topics:

- LSA Types

- Link Cost

- Flooding and LSA Group Pacing

- Link-State Database

LSA Types

Table 7-1 LSA Types

Type

Name

Description

1

Router LSA

LSA sent by every router. This LSA includes the state and cost of all links but does not include prefix information. Router LSAs trigger an SPF recalculation. Router LSAs are flooded to the local OSPFv3 area.

2

Network LSA

LSA sent by the DR. This LSA lists all routers in the multi-access network but does not include prefix information. Network LSAs trigger an SPF recalculation. See the “Designated Routers” section.

3

Inter-Area Prefix LSA

LSA sent by the area border router to an external area for each destination in local area. This LSA includes the link cost from the border router to the local destination. See the “Areas” section.

4

Inter-Area Router LSA

LSA sent by the area border router to an external area. This LSA advertises the link cost to the ASBR only. See the “Areas” section.

5

AS External LSA

LSA generated by the ASBR. This LSA includes the link cost to an external autonomous system destination. AS External LSAs are flooded throughout the autonomous system. See the “Areas” section.

7

Type-7 LSA

LSA generated by the ASBR within an NSSA. This LSA includes the link cost to an external autonomous system destination. Type-7 LSAs are flooded only within the local NSSA. See the “Areas” section.

8

Link LSA

LSA sent by every router, using a link-local flooding scope (see the “Flooding and LSA Group Pacing” section. This LSA includes the link-local address and IPv6 prefixes for this link.

9

Intra-Area Prefix LSA

LSA sent by every router. This LSA includes any prefix or link state changes. Intra-Area Prefix LSAs are flooded to the local OSPFv3 area. This LSA does not trigger an SPF recalculation.

11

Grace LSAs

LSA sent by a restarting router, using a link-local flooding scope. This LSA is used for a graceful restart of OSPFv3. See the “High Availability and Graceful Restart” section.

Link Cost

Each OSPFv3 interface is assigned a link cost. The cost is an arbitrary number. By default, Cisco NX-OS assigns a cost that is the configured reference bandwidth divided by the interface bandwidth. By default, the reference bandwidth is 40 Gb/s. The link cost is carried in the LSA updates for each link.

Flooding and LSA Group Pacing

OSPFv3 floods LSA updates to different sections of the network, depending on the LSA type. OSPFv3 uses the following flooding scopes:

- Link-local—LSA is flooded only on the local link. Used for Link LSAs and Grace LSAs.

- Area-local—LSA is flooded throughout a single OSPF area only. Used for Router LSAs, Network LSAs, Inter-Area-Prefix LSAs, Inter-Area-Router LSAs, and Intra-Area-Prefix LSAs.

- AS scope—LSA is flooded throughout the routing domain. An AS scope is used for AS External LSAs.

LSA flooding guarantees that all routers in the network have identical routing information. LSA flooding depends on the OSPFv3 area configuration (see the “Areas” section). The LSAs are flooded based on the link-state refresh time (every 30 minutes by default). Each LSA has its own link-state refresh time.

You can control the flooding rate of LSA updates in your network by using the LSA group pacing feature. LSA group pacing can reduce high CPU or buffer utilization. This feature groups LSAs with similar link-state refresh times to allow OSPFv3 to pack multiple LSAs into an OSPFv3 Update message.

By default, LSAs with link-state refresh times within 10 seconds of each other are grouped together. You should lower this value for large link-state databases or raise it for smaller databases to optimize the OSPFv3 load on your network.

Link-State Database

Each router maintains a link-state database for the OSPFv3 network. This database contains all the collected LSAs and includes information on all the routes through the network. OSPFv3 uses this information to calculate the bast path to each destination and populates the routing table with these best paths.

LSAs are removed from the link-state database if no LSA update has been received within a set interval, called the MaxAge. Routers flood a repeat of the LSA every 30 minutes to prevent accurate link-state information from being aged out. Cisco NX-OS supports the LSA grouping feature to prevent all LSAs from refreshing at the same time. For more information, see the “Flooding and LSA Group Pacing” section.

Multi-Area Adjacency

OSPFv3 multi-area adjacency allows you to configure a link on the primary interface that is in more than one area. This link becomes the preferred intra-area link in those areas. Multi-area adjacency establishes a point-to-point unnumbered link in an OSPFv3 area that provides a topological path for that area. The primary adjacency uses the link to advertise an unnumbered point-to-point link in the Router LSA for the corresponding area when the neighbor state is full.

The multi-area interface exists as a logical construct over an existing primary interface for OSPF; however, the neighbor state on the primary interface is independent of the multi-area interface. The multi-area interface establishes a neighbor relationship with the corresponding multi-area interface on the neighboring router. See the “Configuring Multi-Area Adjacency” section for more information.

OSPFv3 and the IPv6 Unicast RIB

OSPFv3 runs the Dijkstra shortest path first algorithm on the link-state database. This algorithm selects the best path to each destination based on the sum of all the link costs for each link in the path. The shortest path for each destination is then put in the OSPFv3 route table. When the OSPFv3 network is converged, this route table feeds into the IPv6 unicast RIB. OSPFv3 communicates with the IPv6 unicast RIB to do the following:

- Add or remove routes

- Handle route redistribution from other protocols

- Provide convergence updates to remove stale OSPFv3 routes and for stub router advertisements (see the “Multiple OSPFv3 Instances” section)

OSPFv3 also runs a modified Dijkstra algorithm for fast recalculation for Inter-Area Prefix, Inter-Area Router, AS-External, type-7, and Intra-Area Prefix (type 3, 4, 5, 7, 8) LSA changes.

Address Family Support

Cisco NX-OS supports multiple address families, such as unicast IPv6 and multicast IPv6. OSPFv3 features that are specific to an address family are as follows:

- Default routes

- Route summarization

- Route redistribution

- Filter lists for border routers

- SPF optimization

Use the address-family ipv6 unicast command to enter the IPv6 unicast address family configuration mode when configuring these features.

Advanced Features

Cisco NX-OS supports advanced OSPFv3 features that enhance the usability and scalability of OSPFv3 in the network.

This section includes the following topics:

- Stub Area

- Not-So-Stubby Area

- Virtual Links

- Route Redistribution

- Route Summarization

- High Availability and Graceful Restart

- Multiple OSPFv3 Instances

- SPF Optimization

- Virtualization Support

Stub Area

You can limit the amount of external routing information that floods an area by making it a stub area. A stub area is an area that does not allow AS External (type 5) LSAs (see the “Link-State Advertisement” section). These LSAs are usually flooded throughout the local autonomous system to propagate external route information. Stub areas have the following requirements:

- All routers in the stub area are stub routers. See the “Stub Routing” section.

- No ASBR routers exist in the stub area.

- You cannot configure virtual links in the stub area.

Figure 7-3 shows an example an OSPFv3 autonomous system where all routers in area 0.0.0.10 have to go through the ABR to reach external autonomous systems. Area 0.0.0.10 can be configured as a stub area.

Figure 7-3 Stub Area

Stub areas use a default route for all traffic that needs to go through the backbone area to the external autonomous system. The default route is an Inter-Area-Prefix LSA with the prefix length set to 0 for IPv6.

Not-So-Stubby Area

A Not-So-Stubby Area (NSSA) is similar to the stub area, except that an NSSA allows you to import autonomous system external routes within an NSSA using redistribution. The NSSA ASBR redistributes these routes and generates type-7 LSAs that it floods throughout the NSSA. You can optionally configure the ABR that connects the NSSA to other areas to translate this type-7 LSA to AS External (type 5) LSAs. The ABR then floods these AS External LSAs throughout the OSPFv3 autonomous system. Summarization and filtering are supported during the translation. See the “Link-State Advertisement” section for details on type-7 LSAs.

You can, for example, use NSSA to simplify administration if you are connecting a central site using OSPFv3 to a remote site that is using a different routing protocol. Before NSSA, the connection between the corporate site border router and a remote router could not be run as an OSPFv3 stub area because routes for the remote site could not be redistributed into a stub area. With NSSA, you can extend OSPFv3 to cover the remote connection by defining the area between the corporate router and remote router as an NSSA (see the “Configuring NSSA” section).

The backbone Area 0 cannot be an NSSA.

Virtual Links

Virtual links allow you to connect an OSPFv3 area ABR to a backbone area ABR when a direct physical connection is not available. Figure 7-4 shows a virtual link that connects Area 3 to the backbone area through Area 5.

Figure 7-4 Virtual Links

You can also use virtual links to temporarily recover from a partitioned area, which occurs when a link within the area fails, isolating part of the area from reaching the designated ABR to the backbone area.

Route Redistribution

OSPFv3 can learn routes from other routing protocols by using route redistribution. See the “Route Redistribution” section. You configure OSPFv3 to assign a link cost for these redistributed routes or a default link cost for all redistributed routes.

Route redistribution uses route maps to control which external routes are redistributed. You must configure a route map with the redistribution to control which routes are passed into OSPFv2. A route map allows you to filter routes based on attributes such as the destination, origination protocol, route type, route tag, and so on. You can use route maps to modify parameters in the AS External (type 5) and NSSA External (type 7) LSAs before these external routes are advertised in the local OSPFv3 autonomous system. For more information, see “Configuring Route Policy Manager,”

Route Summarization

Because OSPFv3 shares all learned routes with every OSPF-enabled router, you might want to use route summarization to reduce the number of unique routes that are flooded to every OSPF-enabled router. Route summarization simplifies route tables by replacing more-specific addresses with an address that represents all the specific addresses. For example, you can replace 2010:11:22:0:1000::1 and 2010:11:22:0:2000:679:1 with one summary address, 2010:11:22::/32.

Typically, you would summarize at the boundaries of area border routers (ABRs). Although you could configure summarization between any two areas, it is better to summarize in the direction of the backbone so that the backbone receives all the aggregate addresses and injects them, already summarized, into other areas. The two types of summarization are as follows:

- Inter-area route summarization

- External route summarization

You configure inter-area route summarization on ABRs, summarizing routes between areas in the autonomous system. To take advantage of summarization, assign network numbers in areas in a contiguous way to be able to lump these addresses into one range.

External route summarization is specific to external routes that are injected into OSPFv3 using route redistribution. You should make sure that external ranges that are being summarized are contiguous. Summarizing overlapping ranges from two different routers could cause packets to be sent to the wrong destination. Configure external route summarization on ASBRs that are redistributing routes into OSPF.

When you configure a summary address, Cisco NX-OS automatically configures a discard route for the summary address to prevent routing black holes and route loops.

High Availability and Graceful Restart

Cisco NX-OS provides a multilevel high-availability architecture. OSPFv3 supports stateful restart, which is also referred to as non-stop routing (NSR). If OSPFv3 experiences problems, it attempts to restart from its previous run-time state. The neighbors do not register any neighbor event in this case. If the first restart is not successful and another problem occurs, OSPFv3 attempts a graceful restart.

A graceful restart, or non-stop forwarding (NSF), allows OSPFv3 to remain in the data forwarding path through a process restart. When OSPFv3 needs to perform a graceful restart, it sends a link-local Grace (type 11) LSA. This restarting OSPFv3 platform is called NSF capable.

The Grace LSA includes a grace period, which is a specified time that the neighbor OSPFv3 interfaces hold onto the LSAs from the restarting OSPFv3 interface. (Typically, OSPFv3 tears down the adjacency and discards all LSAs from a down or restarting OSPFv3 interface.) The participating neighbors, which are called NSF helpers, keep all LSAs that originate from the restarting OSPFv3 interface as if the interface was still adjacent.

When the restarting OSPFv3 interface is operational again, it rediscovers its neighbors, establishes adjacency, and starts sending its LSA updates again. At this point, the NSF helpers recognize that the graceful restart has finished.

Stateful restart is used in the following scenarios:

- First recovery attempt after the process experiences problems

- ISSU

- User-initiated switchover using the system switchover command

Graceful restart is used in the following scenarios:

- Second recovery attempt after the process experiences problems within a 4-minute interval

- Manual restart of the process using the restart ospfv3 command

- Active supervisor removal

- Active supervisor reload using the reload module active-sup command

Multiple OSPFv3 Instances

Cisco NX-OS supports multiple instances of the OSPFv3 protocol. By default, every instance uses the same system router ID. You must manually configure the router ID for each instance if the instances are in the same OSPFv3 autonomous system.

The OSPFv3 header includes an instance ID field to identify that OSPFv3 packet for a particular OSPFv3 instance. You can assign the OSPFv3 instance. The interface drops all OSPFv3 packets that do not have a matching OSPFv3 instance ID in the packet header.

Cisco NX-OS allows only one OSPFv3 instance on an interface.

SPF Optimization

Cisco NX-OS optimizes the SPF algorithm in the following ways:

- Partial SPF for Network (type 2) LSAs, Inter-Area Prefix (type 3) LSAs, and AS External (type 5) LSAs—When there is a change on any of these LSAs, Cisco NX-OS performs a faster partial calculation rather than running the whole SPF calculation.

- SPF timers—You can configure different timers for controlling SPF calculations. These timers include exponential backoff for subsequent SPF calculations. The exponential backoff limits the CPU load of multiple SPF calculations.

Virtualization Support

OSPFv3 supports virtual routing and forwarding (VRF) instances. VRFs exist within virtual device contexts (VDCs). By default, Cisco NX-OS places you in the default VDC and default VRF unless you specifically configure another VDC and VRF. Each OSPFv3 instance can support multiple VRFs, up to the system limit. For more information, see the Cisco Nexus 7000 Series NX-OS Virtual Device Context Configuration Guide, Release 5.x, and see Chapter14, “Configuring Layer 3 Virtualization”

Licensing Requirements for OSPFv3

The following table shows the licensing requirements for this feature:

Product

License Requirement

Cisco NX-OS

OSPFv3 requires an Enterprise Services license. For a complete explanation of the Cisco NX-OS licensing scheme and how to obtain and apply licenses, see the Cisco NX-OS Licensing Guide.

Prerequisites for OSPFv3

OSPFv3 has the following prerequisites:

- You must be familiar with routing fundamentals to configure OSPFv3.

- You must be logged on to the switch.

- You have configured at least one interface for IPv6 that is capable of communicating with a remote OSPFv3 neighbor.

- You have installed the Enterprise Services license.

- You have completed the OSPFv3 network strategy and planning for your network. For example, you must decide whether multiple areas are required.

- You have enabled OSPF (see the “Enabling OSPFv3” section).

- You have installed the Advanced Services license and entered the desired VDC (see the Cisco Nexus 7000 Series NX-OS Virtual Device Context Configuration Guide, Release 5.x) if you are configuring VDCs.

- You are familiar with IPv6 addressing and basic configuration. See Chapter 3, “Configuring IPv6” for information on IPv6 routing and addressing.

Guidelines and Limitations for OSPFv3

OSPFv3 has the following configuration guidelines and limitations:

- You can have up to four instances of OSPFv3 in a VDC.

- BFD is not supported for OSPFv3.

- Cisco NX-OS displays areas in dotted decimal notation regardless of whether you enter the area in decimal or dotted decimal notation.

- If you configure OSPFv3 in a virtual port channel (vPC) environment, use the following timer commands in router configuration mode on the core switch to ensure fast OSPF convergence when a vPC peer link is shut down:

switch (config-router)# timers throttle spf 1 50 50

switch (config-router)# timers lsa-arrival 10

Note If you are familiar with the Cisco IOS CLI, be aware that the Cisco NX-OS commands for this feature might differ from the Cisco IOS commands that you would use.

Default Settings

Table 7-2 Default OSPFv3 Parameters

Parameters

Default

Hello interval

10 seconds

Dead interval

40 seconds

Graceful restart grace period

60 seconds

Graceful restart notify period

15 seconds

OSPFv3 feature

Disabled

Stub router advertisement announce time

600 seconds

Reference bandwidth for link cost calculation

40 Gb/s

LSA minimal arrival time

1000 milliseconds

LSA group pacing

10 seconds

SPF calculation initial delay time

0 milliseconds

SPF calculation hold time

5000 milliseconds

SPF calculation initial delay time

0 milliseconds

Configuring Basic OSPFv3

Configure OSPFv3 after you have designed your OSPFv3 network.

This section includes the following topics:

- Enabling OSPFv3

- Creating an OSPFv3 Instance

- Configuring Networks in OSPFv3

Enabling OSPFv3

You must enable OSPFv3 before you can configure OSPFv3.

BEFORE YOU BEGIN

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. feature ospfv3

3. (Optional) show feature

4. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

feature ospfv3

Example:

switch(config)# feature ospfv3

Enables OSPFv3.

Step 3

show feature

Example:

switch(config)# show feature

(Optional) Displays enabled and disabled features.

Step 4

copy running-config startup-config

Example:

switch(config)# copy running-config startup-config

(Optional) Saves this configuration change.

To disable the OSPFv3 feature and remove all associated configuration, use the following command in configuration mode.

Command

Purpose

no feature ospfv3

Example:

switch(config)# no feature ospfv3

Disables the OSPFv3 feature and removes all associated configuration.

Creating an OSPFv3 Instance

The first step in configuring OSPFv3 is to create an instance or OSPFv3 instance. You assign a unique instance tag for this OSPFv3 instance. The instance tag can be any string. For each OSPFv3 instance, you can also configure the following optional parameters:

- Router ID—Configures the router ID for this OSPFv3 instance. If you do not use this parameter, the router ID selection algorithm is used. For more information, see the “Router IDs” section.

- Administrative distance—Rates the trustworthiness of a routing information source. For more information, see the “Administrative Distance” section.

- Log adjacency changes—Creates a system message whenever an OSPFv3 neighbor changes its state.

- Maximum paths—Sets the maximum number of equal paths that OSPFv3 installs in the route table for a particular destination. Use this parameter for load balancing between multiple paths.

- Reference bandwidth—Controls the calculated OSPFv3 cost metric for a network. The calculated cost is the reference bandwidth divided by the interface bandwidth. You can override the calculated cost by assigning a link cost when a network is added to the OSPFv3 instance. For more information, see the “Configuring Networks in OSPFv3” section.

For more information about OSPFv3 instance parameters, see the“Configuring Advanced OSPFv3” section.

BEFORE YOU BEGIN

You must enable OSPFv3 (see the “Enabling OSPFv3” section).

Ensure that the OSPFv3 instance tag that you plan on using is not already in use on this router.

Use the show ospfv3 instance-tag command to verify that the instance tag is not in use.

OSPFv3 must be able to obtain a router identifier (for example, a configured loopback address) or you must configure the router ID option.

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. router ospfv3 instance-tag

3. (Optional) router-id ip-address

4. (Optional) show ipv6 ospfv3 instance-tag

5. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

router ospfv3 instance-tag

Example:

switch(config)# router ospfv3 201

switch(config-router)#

Creates a new OSPFv3 instance with the configured instance tag.

Step 3

router-id ip-address

Example:

switch(config-router)# router-id 192.0.2.1

(Optional) Configures the OSPFv3 router ID. This ID uses the dotted decimal notation and identifies this OSPFv3 instance and must exist on a configured interface in the system.

Step 4

show ipv6 ospfv3 instance-tag

Example:

switch(config-router)# show ipv6 ospfv3 201

(Optional) Displays OSPFv3 information.

Step 5

copy running-config startup-config

Example:

switch(config)# copy running-config startup-config

(Optional) Saves this configuration change.

To remove the OSPFv3 instance and all associated configuration, use the following command in configuration mode:

Command

Purpose

no router ospfv3 instance-tag

Example:

switch(config)# no router ospfv3 201

Deletes the OSPFv3 instance and all associated configuration.

Note This command does not remove OSPF configuration in interface mode. You must manually remove any OSPFv3 commands configured in interface mode.

Command

Purpose

log-adjacency-changes [detail]

Example:

switch(config-router)# log-adjacency-changes

Generates a system message whenever a neighbor changes state.

passive-interface default

Example:

switch(config-router)# passive-interface default

Suppresses routing updates on all interfaces. This command is overridden by the VRF or interface command mode configuration.

You can configure the following optional parameters for OSPFv3 in address family configuration mode:

Command

Purpose

distance number

Example:

switch(config-router-af)# distance 25

Configures the administrative distance for this OSPFv3 instance. The range is from 1 to 255. The default is 110.

maximum-paths paths

Example:

switch(config-router-af)# maximum-paths 4

Configures the maximum number of equal OSPFv3 paths to a destination in the route table. The range is from 1 to 16. The default is 8. This command is used for load balancing.

This example shows how to create an OSPFv3 instance:

switch# configure terminal

switch(config)# router ospfv3 201

switch(config-router)# copy running-config startup-config

Configuring Networks in OSPFv3

You can configure a network to OSPFv3 by associating it through the interface that the router uses to connect to that network (see the “Neighbors” section). You can add all networks to the default backbone area (Area 0), or you can create new areas using any decimal number or an IP address.

Note All areas must connect to the backbone area either directly or through a virtual link.

Note OSPFv3 is not enabled on an interface until you configure a valid IPv6 address for that interface.

BEFORE YOU BEGIN

You must enable OSPFv3 (see the “Enabling OSPFv3” section).

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. interface interface-type slot/port

3. ipv6 address ipv6-prefix/length

4. ipv6 router ospfv3 instance-tag area area-id [secondaries none]

5. (Optional) show ipv6 ospfv3 instance-tag interface interface-type slot/port

6. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

interface interface-type slot/port

Example:

switch(config)# interface ethernet 1/2

switch(config-if)#

Enters interface configuration mode.

Step 3

ipv6 address ipv6-prefix/length

Example:

switch(config-if)# ipv6 address 2001:0DB8::1/48

Assigns an IPv6 address to this interface.

Step 4

ipv6 router ospfv3 instance-tag area area-id [secondaries none]

Example:

switch(config-if)# ipv6 router ospfv3 201 area 0

Adds the interface to the OSPFv3 instance and area.

Step 5

show ipv6 ospfv3 instance-tag interface interface-type slot/port

Example:

switch(config-if)# show ipv6 ospfv3 201 interface ethernet 1/2

(Optional) Displays OSPFv3 information.

Step 6

copy running-config startup-config

Example:

switch(config)# copy running-config startup-config

(Optional) Saves this configuration change.

You can configure the following optional parameters for OSPFv3 in interface configuration mode:

Command

Purpose

ospfv3 cost number

Example:

switch(config-if)# ospfv3 cost 25

Configures the OSPFv3 cost metric for this interface. The default is to calculate a cost metric, based on the reference bandwidth and interface bandwidth. The range is from 1 to 65535.

ospfv3 dead-interval seconds

Example:

switch(config-if)# ospfv3 dead-interval 50

Configures the OSPFv3 dead interval, in seconds. The range is from 1 to 65535. The default is four times the hello interval, in seconds.

ospfv3 hello-interval seconds

Example:

switch(config-if)# ospfv3 hello-interval 25

Configures the OSPFv3 hello interval, in seconds. The range is from 1 to 65535. The default is 10 seconds.

ospfv3 instance instance

Example:

switch(config-if)# ospfv3 instance 25

Configures the OSPFv3 instance ID. The range is from 0 to 255. The default is 0. The instance ID is link-local in scope.

ospfv3 mtu-ignore

Example:

switch(config-if)# ospfv3 mtu-ignore

Configures OSPFv3 to ignore any IP maximum transmission unit (MTU) mismatch with a neighbor. The default is to not establish adjacency if the neighbor MTU does not match the local interface MTU.

ospfv3 network {broadcast | point-point}

Example:

switch(config-if)# ospfv3 network broadcast

Sets the OSPFv3 network type.

[default | no] ospfv3 passive-interface

Example:

switch(config-if)# ospfv3 passive-interface

ospfv3 priority number

Example:

switch(config-if)# ospfv3 priority 25

Configures the OSPFv3 priority, used to determine the DR for an area. The range is from 0 to 255. The default is 1. See the “Designated Routers” section.

ospfv3 shutdown

Example:

switch(config-if)# ospfv3 shutdown

Shuts down the OSPFv3 instance on this interface.

This example shows how to add a network area 0.0.0.10 in OSPFv3 instance 201:

switch# configure terminal

switch(config)# interface ethernet 1/2

switch(config-if)# ipv6 address 2001:0DB8::1/48

switch(config-if)# ipv6 ospfv3 201 area 0.0.0.10

switch(config-if)# copy running-config startup-config

Configuring Advanced OSPFv3

Configure OSPFv3 after you have designed your OSPFv3 network.

This section includes the following topics:

- Configuring Filter Lists for Border Routers

- Configuring Stub Areas

- Configuring a Totally Stubby Area

- Configuring NSSA

- Configuring Multi-Area Adjacency

- Configuring Virtual Links

- Configuring Redistribution

- Limiting the Number of Redistributed Routes

- Configuring Route Summarization

- Modifying the Default Timers

- Configuring Graceful Restart

- Restarting an OSPFv3 Instance

- Configuring OSPFv3 with Virtualization

Configuring Filter Lists for Border Routers

You can separate your OSPFv3 domain into a series of areas that contain related networks. All areas must connect to the backbone area through an area border router (ABR). OSPFv3 domains can connect to external domains as well through an autonomous system border router (ASBR). See the “Areas” section.

ABRs have the following optional configuration parameters:

- Area range—Configures route summarization between areas. For more information, see the “Configuring Route Summarization” section.

- Filter list—Filters the Inter-Area Prefix (type 3) LSAs on an ABR that are allowed in from an external area.

ASBRs also support filter lists.

BEFORE YOU BEGIN

Create the route map that the filter list uses to filter IP prefixes in incoming or outgoing Inter-Area Prefix (type 3) LSAs. See Chapter16, “Configuring Route Policy Manager”

You must enable OSPFv3 (see the “Enabling OSPFv3” section).

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. router ospfv3 instance-tag

3. address-family ipv6 unicast

4. area area-id filter-list route-map map-name {in | out}

5. (Optional) show ipv6 ospfv3 policy statistics area id filter-list {in | out}

6. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

router ospfv3 instance-tag

Example:

switch(config)# router ospfv3 201

switch(config-router)#

Creates a new OSPFv3 instance with the configured instance tag.

Step 3

address-family ipv6 unicast

Example:

switch(config-router)# address-family ipv6 unicast

switch(config-router-af)#

Enters IPv6 unicast address family mode.

Step 4

area area-id filter-list route-map map-name {in | out}

Example:

switch(config-router-af)# area 0.0.0.10 filter-list route-map FilterLSAs in

Filters incoming or outgoing Inter-Area Prefix (type 3) LSAs on an ABR.

Step 5

show ipv6 ospfv3 policy statistics area id filter-list {in | out}

Example:

switch(config-if)# show ipv6 ospfv3 policy statistics area 0.0.0.10 filter-list in

(Optional) Displays OSPFv3 policy information.

Step 6

copy running-config startup-config

Example:

switch(config-router)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to enable graceful restart if it has been disabled:

switch# configure terminal

switch(config)# router ospfv3 201

switch(config-router)# address-family ipv6 unicast

switch(config-router-af)# area 0.0.0.10 filter-list route-map FilterLSAs in

switch(config-router-af)# copy running-config startup-config

Configuring Stub Areas

You can configure a stub area for part of an OSPFv3 domain where external traffic is not necessary. Stub areas block AS External (type 5) LSAs, limiting unnecessary routing to and from selected networks. See the “Stub Area” section. You can optionally block all summary routes from going into the stub area.

BEFORE YOU BEGIN

You must enable OSPF (see the “Enabling OSPFv3” section).

Ensure that there are no virtual links or ASBRs in the proposed stub area.

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. router ospfv3 instance-tag

3. area area-id stub

4. (Optional) address-family ipv6 unicast

5. (Optional) area area-id default-cost cost

6. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

router ospfv3 instance-tag

Example:

switch(config)# router ospfv3 201

switch(config-router)#

Creates a new OSPFv3 instance with the configured instance tag.

Step 3

area area-id stub

Example:

switch(config-router)# area 0.0.0.10 stub

Creates this area as a stub area.

Step 4

address-family ipv6 unicast

Example:

switch(config-router)# address-family ipv6 unicast

switch(config-router-af)#

(Optional) Enters IPv6 unicast address family mode.

Step 5

area area-id default-cost cost

Example:

switch(config-router-af)# area 0.0.0.10 default-cost 25

(Optional) Sets the cost metric for the default summary route sent into this stub area. The range is from 0 to 16777215.

Step 6

copy running-config startup-config

Example:

switch(config-router)# copy running-config startup-config

This shows how to create a stub area that blocks all summary route updates:

switch# configure terminal

switch(config)# router ospfv3 201

switch(config-router)# area 0.0.0.10 stub no-summary

switch(config-router)# copy running-config startup-config

Configuring a Totally Stubby Area

You can create a totally stubby area and prevent all summary route updates from going into the stub area.

To create a totally stubby area, use the following command in router configuration mode:

Command

Purpose

area area-id stub no-summary

Example:

switch(config-router)# area 20 stub no-summary

Creates this area as a totally stubby area.

Configuring NSSA

You can configure an NSSA for part of an OSPFv3 domain where limited external traffic is required. See the “Not-So-Stubby Area” section. You can optionally translate this external traffic to an AS External (type 5) LSA and flood the OSPFv3 domain with this routing information. An NSSA can be configured with the following optional parameters:

- No redistribution— Redistributes routes that bypass the NSSA to other areas in the OSPFv3 autonomous system. Use this option when the NSSA ASBR is also an ABR.

- Default information originate—Generates a Type-7 LSA for a default route to the external autonomous system. Use this option on an NSSA ASBR if the ASBR contains the default route in the routing table. This option can be used on an NSSA ABR whether or not the ABR contains the default route in the routing table.

- Route map—Filters the external routes so that only those routes you want are flooded throughout the NSSA and other areas.

- Translate—Translates Type-7 LSAs to AS External (type 5) LSAs for areas outside the NSSA. Use this command on an NSSA ABR to flood the redistributed routes throughout the OSPFv3 autonomous system. You can optionally suppress the forwarding address in these AS External LSAs.

- No summary—Blocks all summary routes from flooding the NSSA. Use this option on the NSSA ABR.

BEFORE YOU BEGIN

You must enable OSPF (see the “Enabling OSPFv3” section).

Ensure that there are no virtual links in the proposed NSSA and that it is not the backbone area.

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. router ospfv3 instance-tag

3. area area-id nssa [no-redistribution] [default-information-originate] [route-map map-name] [no-summary] [translate type7 {always | never} [suppress-fa]]

4. (Optional) address-family ipv6 unicast

5. (Optional) area area-id default-cost cost

6. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

router ospfv3 instance-tag

Example:

switch(config)# router ospfv3 201

switch(config-router)#

Creates a new OSPFv3 instance with the configured instance tag.

Step 3

area area-id nssa [no-redistribution] [default-information-originate]

[route-map map-name][no-summary] [translate type7 {always | never} [suppress-fa]]

Example:

switch(config-router)# area 0.0.0.10 nssa

Creates this area as an NSSA.

Step 4

address-family ipv6 unicast

Example:

switch(config-router)# address-family ipv6 unicast

switch(config-router-af)#

(Optional) Enters IPv6 unicast address family mode.

Step 5

area area-id default-cost cost

Example:

switch(config-router-af)# area 0.0.0.10 default-cost 25

(Optional) Sets the cost metric for the default summary route sent into this NSSA. The range is from 0 to 16777215.

Step 6

copy running-config startup-config

Example:

switch(config-router)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to create an NSSA that blocks all summary route updates:

switch# configure terminal

switch(config)# router ospfv3 201

switch(config-router)# area 0.0.0.10 nssa no-summary

switch(config-router)# copy running-config startup-config

This example shows how to create an NSSA that generates a default route:

switch# configure terminal

switch(config)# router ospfv3 201

switch(config-router)# area 0.0.0.10 nssa default-info-originate

switch(config-router)# copy running-config startup-config

This example shows how to create an NSSA that filters external routes and blocks all summary route updates:

switch# configure terminal

switch(config)# router ospfv3 201

switch(config-router)# area 0.0.0.10 nssa route-map ExternalFilter no-summary

switch(config-router)# copy running-config startup-config

This example shows how to create an NSSA that always translates Type-7 LSAs to AS External (type 5) LSAs:

switch# configure terminal

switch(config)# router ospfv3 201

switch(config-router)# area 0.0.0.10 nssa translate type 7 always

switch(config-router)# copy running-config startup-config

This example shows how to create an NSSA that blocks all summary route updates:

switch# configure terminal

switch(config)# router ospfv3 201

switch(config-router)# area 0.0.0.10 nssa no-summary

switch(config-router)# copy running-config startup-config

Configuring Multi-Area Adjacency

You can add more than one area to an existing OSPFv3 interface. The additional logical interfaces support multi-area adjacency.

BEFORE YOU BEGIN

You must enable OSPFv3 (see the “Enabling OSPFv3” section).

Ensure that you are in the correct VDC (or use the switchto vdc command).

Ensure that you have configured a primary area for the interface (see the “Configuring Networks in OSPFv3” section

SUMMARY STEPS

1. configure terminal

2. interface interface-type slot/port

3. ipv6 router ospfv3 instance-tag multi-area area-id

4. (Optional) show ipv6 ospfv3 instance-tag interface interface-type slot/port

5. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

interface interface-type slot/port

Example:

switch(config)# interface ethernet 1/2

switch(config-if)#

Enters interface configuration mode.

Step 3

ipv6 router ospfv3 instance-tag multi-area area-id

Example:

switch(config-if)# ipv6 router ospfv3 201 multi-area 3

Adds the interface to another area.

Step 4

show ipv6 ospfv3 instance-tag interface interface-type slot/port

Example:

switch(config-if)# show ipv6 ospfv3 201 interface ethernet 1/2

(Optional) Displays OSPFv3 information.

Step 5

copy running-config startup-config

Example:

switch(config)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to add a second area to an OSPFv3 interface:

switch# configure terminal

switch(config)# interface ethernet 1/2

switch(config-if)# ipv6 address 2001:0DB8::1/48

switch(config-if)# ipv6 ospfv3 201 area 0.0.0.10

switch(config-if)# ipv6 ospfv3 201 multi-area 20

switch(config-if)# copy running-config startup-config

Configuring Virtual Links

A virtual link connects an isolated area to the backbone area through an intermediate area. See the “Virtual Links” section. You can configure the following optional parameters for a virtual link:

- Dead interval—Sets the time that a neighbor waits for a Hello packet before declaring the local router as dead and tearing down adjacencies.

- Hello interval—Sets the time between successive Hello packets.

- Retransmit interval—Sets the estimated time between successive LSAs.

- Transmit delay—Sets the estimated time to transmit an LSA to a neighbor.

Note You must configure the virtual link on both routers involved before the link becomes active.

BEFORE YOU BEGIN

You must enable OSPF (see the “Enabling OSPFv3” section).

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. router ospfv3 instance-tag

3. area area-id virtual-link router-id

4. (Optional) show ipv6 ospfv3 virtual-link [brief]

5. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

router ospfv3 instance-tag

Example:

switch(config)# router ospfv3 201

switch(config-router)#

Creates a new OSPFv3 instance with the configured instance tag.

Step 3

area area-id virtual-link router-id

Example:

switch(config-router)# area 0.0.0.10 virtual-link 2001:0DB8::1

switch(config-router-vlink)#

Creates one end of a virtual link to a remote router. You must create the virtual link on that remote router to complete the link.

Step 4

show ipv6 ospfv3 virtual-link [brief]

Example:

switch(config-if)# show ipv6 ospfv3 virtual-link

(Optional) Displays OSPFv3 virtual link information.

Step 5

copy running-config startup-config

Example:

switch(config-router)# copy running-config startup-config

(Optional) Saves this configuration change.

You can configure the following optional commands in virtual link configuration mode:

Command

Purpose

dead-interval seconds

Example:

switch(config-router-vlink)# dead-interval 50

(Optional) Configures the OSPFv3 dead interval, in seconds. The range is from 1 to 65535. The default is four times the hello interval, in seconds.

hello-interval seconds

Example:

switch(config-router-vlink)# hello-interval 25

(Optional) Configures the OSPFv3 hello interval, in seconds. The range is from 1 to 65535. The default is 10 seconds.

retransmit-interval seconds

Example:

switch(config-router-vlink)# retransmit-interval 50

(Optional) Configures the OSPFv3 retransmit interval, in seconds. The range is from 1 to 65535. The default is 5.

transmit-delay seconds

Example:

switch(config-router-vlink)# transmit-delay 2

(Optional) Configures the OSPFv3 transmit-delay, in seconds. The range is from 1 to 450. The default is 1.

These examples show how to create a simple virtual link between two ABRs:

Configuration for ABR 1 (router ID 2001:0DB8::1) is as follows:

switch# configure terminal

switch(config)# router ospfv3 201

switch(config-router)# area 0.0.0.10 virtual-link 2001:0DB8::10

switch(config-router)# copy running-config startup-config

Configuration for ABR 2 (router ID 2001:0DB8::10) is as follows:

switch# configure terminal

switch(config)# router ospf 101

switch(config-router)# area 0.0.0.10 virtual-link 2001:0DB8::1

switch(config-router)# copy running-config startup-config

Configuring Redistribution

You can redistribute routes learned from other routing protocols into an OSPFv3 autonomous system through the ASBR.

You can configure the following optional parameters for route redistribution in OSPF:

- Default information originate—Generates an AS External (type 5) LSA for a default route to the external autonomous system.

Note Default information originate ignores match statements in the optional route map.

- Default metric—Sets all redistributed routes to the same cost metric.

Note If you redistribute static routes, Cisco NX-OS also redistributes the default static route.

BEFORE YOU BEGIN

Create the necessary route maps used for redistribution.

You must enable OSPF (see the “Enabling OSPFv3” section).

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. router ospfv3 instance-tag

3. address-family ipv6 unicast

4. redistribute {bgp id | direct | isis id | rip id | static} route-map map-name

5. default-information originate [always] [route-map map-name]

6. default-metric cost

7. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

router ospfv3 instance-tag

Example:

switch(config)# router ospfv3 201

switch(config-router)#

Creates a new OSPFv3 instance with the configured instance tag.

Step 3

address-family ipv6 unicast

Example:

switch(config-router)# address-family ipv6 unicast

switch(config-router-af)#

Enters IPv6 unicast address family mode.

Step 4

redistribute {bgp id | direct | isis id | rip id | static} route-map map-name

Example:

switch(config-router-af)# redistribute bgp route-map FilterExternalBGP

Redistributes the selected protocol into OSPFv3 through the configured route map.

Note If you redistribute static routes, Cisco NX-OS also redistributes the default static route.

Step 5

default-information originate [always] [route-map map-name]

Example:

switch(config-router-af)# default-information-originate route-map DefaultRouteFilter

Creates a default route into this OSPFv3 domain if the default route exists in the RIB. Use the following optional keywords:

- always —Always generates the default route of 0.0.0. even if the route does not exist in the RIB.

- route-map —Generates the default route if the route map returns true.

statements in the route map.

Step 6

default-metric cost

Example:

switch(config-router-af)# default-metric 25

Sets the cost metric for the redistributed routes. The range is from 1 to 16777214. This command does not apply to directly connected routes. Use a route map to set the default metric for directly connected routes.

Step 7

copy running-config startup-config

Example:

switch(config-router)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to redistribute the Border Gateway Protocol (BGP) into OSPFv3:

switch# configure terminal

switch(config)# router ospfv3 201

switch(config-router)# address-family ipv6 unicast

switch(config-router-af)# redistribute bgp route-map FilterExternalBGP

switch(config-router-af)# copy running-config startup-config

Limiting the Number of Redistributed Routes

Route redistribution can add many routes to the OSPFv3 route table. You can configure a maximum limit to the number of routes accepted from external protocols. OSPFv3 provides the following options to configure redistributed route limits:

- Fixed limit—Logs a message when OSPFv3 reaches the configured maximum. OSPFv3 does not accept any more redistributed routes. You can optionally configure a threshold percentage of the maximum where OSPFv3 logs a warning when that threshold is passed.

- Warning only—Logs a warning only when OSPFv3 reaches the maximum. OSPFv3 continues to accept redistributed routes.

- Withdraw—Starts the configured timeout period when OSPFv3 reaches the maximum. After the timeout period, OSPFv3 requests all redistributed routes if the current number of redistributed routes is less than the maximum limit. If the current number of redistributed routes is at the maximum limit, OSPFv3 withdraws all redistributed routes. You must clear this condition before OSPFv3 accepts more redistributed routes. You can optionally configure the timeout period.

BEFORE YOU BEGIN

You must enable OSPF (see the “Enabling OSPFv3” section).

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. router ospfv3 instance-tag

3. address-family ipv6 unicast

4. redistribute {bgp id | direct | isis id | rip id | static} route-map map-name

5. redistribute maximum-prefix max [threshold] [warning-only | withdraw [num-retries timeout]]

6. (Optional) show running-config ospfv3

7. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

router ospfv3 instance-tag

Example:

switch(config)# router ospfv3 201

switch(config-router)#

Creates a new OSPFv3 instance with the configured instance tag.

Step 3

address-family ipv6 unicast

Example:

switch(config-router)# address-family ipv6 unicast

switch(config-router-af)#

Enters IPv6 unicast address family mode.

Step 4

redistribute {bgp id | direct | isis id | rip id | static} route-map map-name

Example:

switch(config-router-af)# redistribute bgp route-map FilterExternalBGP

Redistributes the selected protocol into OSPFv3 through the configured route map.

Step 5

redistribute maximum-prefix max [threshold] [warning-only | withdraw [num-retries timemout]]

Example:

switch(config-router)# redistribute maximum-prefix 1000 75 warning-only

Specifies a maximum number of prefixes that OSPFv2 distributes. The range is from 0 to 65536. Optionally, specifies the following:

- threshold —Percent of maximum prefixes that triggers a warning message.

- warning-only —Logs an warning message when the maximum number of prefixes is exceeded.

- withdraw —Withdraws all redistributed routes and optionally tries to retrieve the redistributed routes. The num-retries range is from 1 to 12. The timeout range is from 60 to 600 seconds. The default is 300 seconds.

Step 6

show running-config ospfv3

Example:

switch(config-router)# show running-config ospf

(Optional) Displays the OSPFv3 configuration.

Step 7

copy running-config startup-config

Example:

switch(config-router)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to limit the number of redistributed routes into OSPF:

switch# configure terminal

switch(config)# router ospfv3 201

switch(config-router)# address-family ipv6 unicast

switch(config-router-af)# redistribute bgp route-map FilterExternalBGP

switch(config-router-af)# redistribute maximum-prefix 1000 75

Configuring Route Summarization

You can configure route summarization for inter-area routes by configuring an address range that is summarized. You can also configure route summarization for external, redistributed routes by configuring a summary address for those routes on an ASBR. For more information, see the “Route Summarization” section.

BEFORE YOU BEGIN

You must enable OSPF (see the “Enabling OSPFv3” section).

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. router ospfv3 instance-tag

3. address-family ipv6 unicast

4. area area-id range ipv6-prefix/length [no-advertise] [cost cost]

or

5. summary-address ipv6-prefix/length [no-advertise] [tag tag]

6. (Optional) show ipv6 ospfv3 summary-address

7. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

router ospfv3 instance-tag

Example:

switch(config)# router ospfv3 201

switch(config-router)#

Creates a new OSPFv3 instance with the configured instance tag.

Step 3

address-family ipv6 unicast

Example:

switch(config-router)# address-family ipv6 unicast

switch(config-router-af)#

Enters IPv6 unicast address family mode.

Step 4

area area-id range ipv6-prefix/length [no-advertise] [cost cost]

Example:

switch(config-router-af)# area 0.0.0.10 range 2001:0DB8::/48 advertise

Creates a summary address on an ABR for a range of addresses and optionally advertises this summary address in a Inter-Area Prefix (type 3) LSA. The cost range is from 0 to 16777215.

Step 5

summary-address ipv6-prefix/length [no-advertise][tag tag]

Example:

switch(config-router-af)# summary-address 2001:0DB8::/48 tag 2

Creates a summary address on an ASBR for a range of addresses and optionally assigns a tag for this summary address that can be used for redistribution with route maps.

Step 6

show ipv6 ospfv3 summary-address

Example:

switch(config-router)# show ipv6 ospfv3 summary-address

(Optional) Displays information about OSPFv3 summary addresses.

Step 7

copy running-config startup-config

Example:

switch(config-router)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to create summary addresses between areas on an ABR:

switch# configure terminal

switch(config)# router ospfv3 201

switch(config-router)# address-family ipv6 unicast

switch(config-router)# area 0.0.0.10 range 2001:0DB8::/48

switch(config-router)# copy running-config startup-config

This example shows how to create summary addresses on an ASBR:

switch# configure terminal

switch(config)# router ospf 201

switch(config-router)# address-family ipv6 unicast

switch(config-router)# summary-address 2001:0DB8::/48

switch(config-router)# copy running-config startup-config

Modifying the Default Timers

OSPFv3 includes a number of timers that control the behavior of protocol messages and shortest path first (SPF) calculations. OSPFv3 includes the following optional timer parameters:

- LSA arrival time—Sets the minimum interval allowed between LSAs arriving from a neighbor. LSAs that arrive faster than this time are dropped.

- Pacing LSAs—Sets the interval at which LSAs are collected into a group and refreshed, checksummed, or aged. This timer controls how frequently LSA updates occur and optimizes how many are sent in an LSA update message (see the “Flooding and LSA Group Pacing” section).

- Throttle LSAs—Sets rate limits for generating LSAs. This timer controls how frequently LSAs are generated after a topology change occurs.

- Throttle SPF calculation—Controls how frequently the SPF calculation is run.

At the interface level, you can also control the following timers:

- Retransmit interval—Sets the estimated time between successive LSAs.

- Transmit delay—Sets the estimated time to transmit an LSA to a neighbor.

See the “Configuring Networks in OSPFv3” section for information on the hello interval and dead timer.

BEFORE YOU BEGIN

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. router ospfv3 instance-tag

3. timers lsa-arrival msec

4. timers lsa-group-pacing seconds

5. timers throttle lsa start-time hold-interval max-time

6. address-family ipv6 unicast

7. timers throttle spf delay-time hold-time

8. interface type slot/port

9. ospfv3 retransmit-interval seconds

10. ospfv3 transmit-delay seconds

11. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

router ospfv3 instance-tag

Example:

switch(config)# router ospfv3 201

switch(config-router)#

Creates a new OSPFv3 instance with the configured instance tag.

Step 3

timers lsa-arrival msec

Example:

switch(config-router)# timers lsa-arrival 2000

Sets the LSA arrival time in milliseconds. The range is from 10 to 600000. The default is 1000 milliseconds.

Step 4

timers lsa-group-pacing seconds

Example:

switch(config-router)# timers lsa-group-pacing 200

Sets the interval in seconds for grouping LSAs. The range is from 1 to 1800. The default is 10 seconds.

Step 5

timers throttle lsa start-time hold-interval max-time

Example:

switch(config-router)# timers throttle lsa network 350 5000 6000

Sets the rate limit in milliseconds for generating LSAs. You can configure the following timers:

start-time—The range is from 50 to 5000 milliseconds. The default value is 50 milliseconds.

hold-interval—The range is from 50 to 30,000 milliseconds. The default value is 5000 milliseconds.

max-time—The range is from 50 to 30,000 milliseconds. The default value is 5000 milliseconds.

Step 6

address-family ipv6 unicast

Example:

switch(config-router)# address-family ipv6 unicast

switch(config-router-af)#

Enters IPv6 unicast address family mode.

Step 7

timers throttle spf delay-time hold-time

Example:

switch(config-router)# timers throttle spf 3000 2000

Sets the SPF best path schedule initial delay time and the minimum hold time in seconds between SPF best path calculations. The range is from 1 to 600000. The default is no delay time and 5000 millisecond hold time.

Step 8

interface type slot/port

Example:

switch(config)# interface ethernet 1/2

switch(config-if)#

Enters interface configuration mode.

Step 9

ospfv3 retransmit-interval seconds

Example:

switch(config-if)# ospfv3 retransmit-interval 30

Sets the estimated time in seconds between LSAs transmitted from this interface. The range is from 1 to 65535. The default is 5.

Step 10

ospfv3 transmit-delay seconds

Example:

switch(config-if)# ospfv3 transmit-delay 600

switch(config-if)#

Sets the estimated time in seconds to transmit an LSA to a neighbor. The range is from 1 to 450. The default is 1.

Step 11

copy running-config startup-config

Example:

switch(config-if)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to control LSA flooding with the lsa-group-pacing option:

switch# configure terminal

switch(config)# router ospf 201

switch(config-router)# timers lsa-group-pacing 300

switch(config-router)# copy running-config startup-config

Configuring Graceful Restart

Graceful restart is enabled by default. You can configure the following optional parameters for graceful restart in an OSPFv3 instance:

- Grace period—Configures how long neighbors should wait after a graceful restart has started before tearing down adjacencies.

- Helper mode disabled—Disables helper mode on the local OSPFv3 instance. OSPFv3 does not participate in the graceful restart of a neighbor.

- Planned graceful restart only—Configures OSPFv3 to support graceful restart only in the event of a planned restart.

BEFORE YOU BEGIN

You must enable OSPFv3 (see the “Enabling OSPFv3” section).

Ensure that all neighbors are configured for graceful restart with matching optional parameters set.

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. router ospfv3 instance-tag

3. graceful-restart

4. graceful-restart grace-period seconds

5. graceful-restart helper-disable

6. graceful-restart planned-only

7. (Optional) show ipv6 ospfv3 instance-tag

8. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

router ospfv3 instance-tag

Example:

switch(config)# router ospfv3 201

switch(config-router)#

Creates a new OSPFv3 instance with the configured instance tag.

Step 3

graceful-restart

Example:

switch(config-router)# graceful-restart

Enables graceful restart. A graceful restart is enabled by default.

Step 4

graceful-restart grace-period seconds

Example:

switch(config-router)# graceful-restart grace-period 120

Sets the grace period, in seconds. The range is from 5 to 1800. The default is 60 seconds.

Step 5

graceful-restart helper-disable

Example:

switch(config-router)# graceful-restart helper-disable

Disables helper mode. Enabled by default.

Step 6

graceful-restart planned-only

Example:

switch(config-router)# graceful-restart planned-only

Configures graceful restart for planned restarts only.

Step 7

show ipv6 ospfv3 instance-tag

Example:

switch(config-if)# show ipv6 ospfv3 201

(Optional) Displays OSPFv3 information.

Step 8

copy running-config startup-config

Example:

switch(config)# copy running-config startup-config

(Optional) Saves this configuration change.

This shows how to enable graceful restart if it has been disabled and set the grace period to 120 seconds:

switch# configure terminal

switch(config)# router ospfv3 201

switch(config-router)# graceful-restart

switch(config-router)# graceful-restart grace-period 120

switch(config-router)# copy running-config startup-config

Restarting an OSPFv3 Instance

You can restart an OSPv3 instance. This action clears all neighbors for the instance.

To restart an OSPFv3 instance and remove all associated neighbors, use the following command:

Command

Purpose

restart ospfv3 instance-tag

Example:

switch(config)# restart ospfv3 201

Restarts the OSPFv3 instance and removes all neighbors.

Configuring OSPFv3 with Virtualization

You can configure multiple OSPFv3 instances in each VDC. You can also create multiple VRFs within each VDC and use the same or multiple OSPFv3 instances in each VRF. You assign an OSPFv3 interface to a VRF.

Note Configure all other parameters for an interface after you configure the VRF for an interface. Configuring a VRF for an interface deletes all the configuration for that interface.

BEFORE YOU BEGIN

Create the VDCs.

You must enable OSPF (see the “Enabling OSPFv3” section).

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. vrf context vrf_name

3. router ospfv3 instance-tag

4. vrf vrf-name

5. (Optional) maximum-paths paths

6. interface type slot/port

7. vrf member vrf-name

8. ipv6 address ipv6-prefix/length

9. ipv6 ospfv3 instance-tag area area-id

10. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

vrf context vrf-name

Example:

switch(config)# vrf context RemoteOfficeVRF

switch(config-vrf)#

Creates a new VRF and enters VRF configuration mode.

Step 3

router ospfv3 instance-tag

Example:

switch(config)# router ospfv3 201

switch(config-router)#

Creates a new OSPFv3 instance with the configured instance tag.

Step 4

vrf vrf-name

Example:

switch(config-router)# vrf RemoteOfficeVRF

switch(config-router-vrf)#

Enters VRF configuration mode.

Step 5

maximum-paths paths

Example:

switch(config-router-vrf)# maximum-paths 4

(Optional) Configures the maximum number of equal OSPFv3 paths to a destination in the route table for this VRF. Use this command for load balancing.

Step 6

interface type slot/port

Example:

switch(config)# interface ethernet 1/2

switch(config-if)#

Enters interface configuration mode.

Step 7

vrf member vrf-name

Example:

switch(config-if)# vrf member RemoteOfficeVRF

Adds this interface to a VRF.

Step 8

ipv6 address ipv6-prefix/length

Example:

switch(config-if)# ipv6 address 2001:0DB8::1/48

Configures an IP address for this interface. You must do this step after you assign this interface to a VRF.

Step 9

ipv6 ospfv3 instance-tag area area-id

Example:

switch(config-if)# ipv6 ospfv3 201 area 0

Assigns this interface to the OSPFv3 instance and area configured.

Step 10

copy running-config startup-config

Example:

switch(config)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to create a VRF and add an interface to the VRF:

switch# configure terminal

switch(config)# vrf context NewVRF

switch(config-vrf)# exit

switch(config)# router ospfv3 201

switch(config-router)# exit

switch(config)# interface ethernet 1/2

switch(config-if)# vrf member NewVRF

switch(config-if)# ipv6 address 2001:0DB8::1/48

switch(config-if)# ipv6 ospfv3 201 area 0

switch(config-if)# copy running-config startup-config

Verifying the OSPFv3 Configuration

Command

Purpose

show ipv6 ospfv3

Displays the OSPFv3 configuration.

show ipv6 ospfv3 border-routers

Displays the internal OSPF routing table entries to an ABR and ASBR.

show ipv6 ospfv3 database

Displays lists of information related to the OSPFv3 database for a specific router.

show ipv6 ospfv3 interface type number [vrf {vrf-name | all | default | management}]

Displays the OSPFv3 interface configuration.

show ipv6 ospfv3 neighbors

Displays the neighbor information. Use the clear ospfv3 neighbors command to remove adjacency with all neighbors.

show ipv6 ospfv3 request-list

Displays a list of LSAs requested by a router.

show ipv6 ospfv3 retransmission-list

Displays a list of LSAs waiting to be retransmitted.

show ipv6 ospfv3 summary-address

Displays a list of all summary address redistribution information configured under an OSPFv3 instance.

show running-configuration ospfv3

Displays the current running OSPFv3 configuration.

Monitoring OSPFv3

Command

Purpose

show ipv6 ospfv3 memory

Displays the OSPFv3 memory usage statistics.

show ipv6 ospfv3 policy statistics area area-id filter-list {in | out} [vrf {vrf-name | all | default | management}]

Displays the OSPFv3 route policy statistics for an area.

show ipv6 ospfv3 policy statistics redistribute {bgp id| direct | isis id | rip id | static} vrf {vrf-name | all | default | management}]

Displays the OSPFv3 route policy statistics.

show ipv6 ospfv3 statistics [vrf {vrf-name | all | default | management}]

Displays the OSPFv3 event counters.

show ipv6 ospfv3 traffic [interface-type number] [vrf {vrf-name | all | default | management}]

Displays the OSPFv3 packet counters.

Configuration Examples for OSPFv3

ipv6 ospfv3 201 area 0.0.0.10

Related Topics

The following topics can give more information on OSPF:

- Chapter 6, “Configuring OSPFv2”

- Chapter 16, “Configuring Route Policy Manager”

Additional References

For additional information related to implementing OSPF, see the following sections:

- Related Documents

- MIBs

Related Documents

Related Topic

Document Title

OSPFv3 CLI commands

Cisco Nexus 7000 Series NX-OS Unicast Routing Command Reference, Release 5.x

VDCs

Cisco Nexus 7000 Series NX-OS Virtual Device Context Configuration Guide, Release 5.x

MIBs

MIBs

MIBs Link

- OSPF-MIB

- OSPF-TRAP-MIB

To locate and download MIBs, go to the following URL:

http://www.cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml

Feature History for OSPFv3

Table 7-3 Feature History for IOSPFv3

Feature Name

Releases

Feature Information

Passive interface

5.2(1)

Added support for setting the passive interface mode on all interfaces in the router or VRF.

OSPFv3

4.0(1)

Configuring Policy-Based Routing

This chapter describes how to configure policy-based routing on the Cisco NX-OS device.

This chapter includes the following sections:

- Information About Policy-Based Routing

- Licensing Requirements for Policy-Based Routing

- Prerequisites for Policy-Based Routing

- Guidelines and Limitations for Policy-Based Routing

- Default Settings

- Configuring Policy-Based Routing

- Verifying the Policy-Based Routing Configuration

- Configuration Examples for Policy-BasedRouting

- Related Topics

- Additional References

- Feature History for Policy-Based Routing

Information About Policy-Based Routing

Policy-based routing allows you to configure a defined policy for IPv4 and IPv6 traffic flows, lessening reliance on routes derived from routing protocols. All packets received on an interface with policy-based routing enabled are passed through enhanced packet filters or route maps. The route maps dictate the policy, determining where to forward packets.

Route maps are composed of match and set statements that you can mark as permit or deny. You can interpret the statements as follows:

- If the packets match any route map statements, all the set statements are applied. One of these actions involves choosing the next hop.

- If a statement is marked as deny, the packets that meet the match criteria are sent back through the normal forwarding channels and destination-based routing is performed.

- If the statement is marked as permit and the packets do not match any route-map statements, the packets are sent back through the normal forwarding channels and destination-based routing is performed.

For more information, see the “Route Maps” section.

Policy-based routing includes the following features:

- Source-based routing—Routes traffic that originates from different sets of users through different connections across the policy routers.

- Quality of Service (QoS)—Differentiates traffic by setting the precedence or type of service (ToS) values in the IP packet headers at the periphery of the network and leveraging queuing mechanisms to prioritize traffic in the core or backbone of the network (see the Cisco Nexus 7000 Series NX-OS Quality of Service Configuration Guide, Release 5.x ).

- Load sharing—Distributes traffic among multiple paths based on the traffic characteristics.

This section includes the following topics:

- Policy Route Maps

- Set Criteria for Policy-Based Routing

Policy Route Maps

Each entry in a route map contains a combination of match and set statements. The match statements define the criteria for whether appropriate packets meet the particular policy (that is, the conditions to be met). The set clauses explain how the packets should be routed once they have met the match criteria.

You can mark the route-map statements as permit or deny. If the statement is marked as a deny, the packets that meet the match criteria are sent back through the normal forwarding channels (destination-based routing is performed). If the statement is marked as permit and the packets meet the match criteria, all the set clauses are applied. If the statement is marked as permit and the packets do not meet the match criteria, those packets are also forwarded through the normal routing channel.

Note Policy routing is specified on the interface that receives the packets, not on the interface from which the packets are sent.

Set Criteria for Policy-Based Routing

The set criteria in a route map is evaluated in the order listed in the route map. Set criteria specific to route maps used for policy-based routing are as follows:

1. List of interfaces through which the packets can be routed—If more than one interface is specified, the first interface that is found to be up is used for forwarding the packets.

2. List of specified IP addresses—The IP address can specify the adjacent next-hop router in the path toward the destination to which the packets should be forwarded. The first IP address associated with a currently up connected interface is used to route the packets.

Note You can optionally configure the set criteria for next-hop addresses to load balance traffic across up to 16 IP addresses. In this case, Cisco NX-OS sends all traffic for each IP flow to a particular IP next-hop address.

3. List of default interfaces—If there is no explicit route available to the destination address of the packet being considered for policy routing, the route map routes it to the first up interface in the list of specified default interfaces.

4. List of default next-hop IP addresses—Route to the interface or the next-hop address specified by this set statement only if there is no explicit route for the destination address of the packet in the routing table.

Note You can optionally configure the set criteria for the default next-hop addresses to load balance traffic across a maximum of 16 IP addresses. In this case, Cisco NX-OS sends all traffic for each IP flow to a particular IP next-hop address.

If the packets do not meet any of the defined match criteria, those packets are routed through the normal destination-based routing process.

Licensing Requirements for Policy-Based Routing

The following table shows the licensing requirements for this feature:

Product

License Requirement

Cisco NX-OS

Policy-based routing requires an Enterprise Services license. For a complete explanation of the Cisco NX-OS licensing scheme and how to obtain and apply licenses, see the Cisco NX-OS Licensing Guide.

Prerequisites for Policy-Based Routing

Policy-based routing has the following prerequisites:

- Install the correct license.

- You must enable policy-based routing (see the “Enabling the Policy-Based Routing Feature” section).

- Assign an IP address on the interface and bring the interface up before you apply a route map on the interface for policy-based routing.

- If you configure VDCs, install the Advanced Services license and enter the desired VDC (see the Cisco NX-OS Virtual Device Context Configuration Guide).

Guidelines and Limitations for Policy-Based Routing

Policy-based routing has the following configuration guidelines and limitations:

- A policy-based routing route map can have only one match or set statement per route-map statement.

- A match command cannot refer to more than one ACL in a single route-map statement/clause.

- Policy-based routing is not supported with inbound traffic on FEX ports.

- An ACL used in a policy-based routing route map cannot include a deny statement.

- The same route map can be shared among different interfaces for policy-based routing as long as the interfaces belong to the same virtual routing and forwarding (VRF) instance.

- Setting a tunnel interface or an IP address via a tunnel interface as a next hop in a policy-based routing policy is not supported.

- Using a prefix-list as a match criteria is not supported. Do not use a prefix-list in a policy-based routing route-map.

- Beginning with Cisco NX-OS Release 5.2(4), policy-based routing and WCCPv2 are supported on the same interface. However, policy-based routing with statistics and WCCPv2 is supported on the same interface only if bank chaining is disabled.

Default Settings

Table 17-1 Default Policy-based Routing Parameters

Parameters

Default

Policy-based routing

Disabled

Configuring Policy-Based Routing

This section includes the following topics:

- Enabling the Policy-Based Routing Feature

- Configuring a Route Policy

Note If you are familiar with the Cisco IOS CLI, be aware that the Cisco NX-OS commands for this feature might differ from the Cisco IOS commands that you would use.

Enabling the Policy-Based Routing Feature

You must enable the policy-based routing feature before you can configure a route policy.

BEFORE YOU BEGIN

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. feature pbr

3. (Optional) show feature

4. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

feature pbr

Example:

switch(config)# feature pbr

Enables the policy-based routing feature.

Step 3

show feature

Example:

switch(config)# show feature

(Optional) Displays enabled and disabled features.

Step 4

copy running-config startup-config

Example:

switch(config)# copy running-config startup-config

(Optional) Saves this configuration change.

Use the no feature pbr command to disable the policy-based routing feature and remove all associated configuration.

Command

Purpose

no feature pbr

Example:

switch(config)# no feature pbr

Disables policy-based routing and removes all associated configuration.

Configuring a Route Policy

You can use route maps in policy-based routing to assign routing policies to the inbound interface. See the “Configuring Route Maps” section.

SUMMARY STEPS

1. configure terminal

2. interface type slot/port

3. ip policy route-map map-name

or

ipv6 policy route-map map-nam

4. (Optional) exit

5. (Optional) exit

6. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

interface type slot/port

Example:

switch(config)# interface ethernet 1/2

switch(config-if)#

Enters interface configuration mode.

Step 3

ip policy route-map map-name

Example:

switch(config-if)# ip policy route-map Testmap

Assigns a route map for IPv4 policy-based routing to the interface.

ipv6 policy route-map map-name

Example:

switch(config-if)# ipv6 policy route-map TestIPv6map

Assigns a route map for IPv6 policy-based routing to the interface.

Step 4

exit

Example:

switch(config-route-map)# exit

(Optional) Exits route-map configuration mode.

Step 5

exit

Example:

switch(config)# exit

(Optional) Exits global configuration mode.

Step 6

copy running-config startup-config

Example:

switch# copy running-config startup-config

This example shows how to add a route map to an interface:

switch# configure terminal

switch(config)# interface ethernet 1/2

switch(config-if)# ip policy route-map Testmap

switch(config)# exit

switch(config)# copy running-config startup-config

You can configure the following optional match parameters for route maps in route-map configuration mode:

Command

Purpose

match ip address access-list-name name [name...]

Example:

switch(config-route-map)# match ip address access-list-name ACL1

Matches an IPv4 address against one or more IP access control lists (ACLs). This command is used for policy-based routing and is ignored by route filtering or redistribution.

match ipv6 address access-list-name name [name...]

Example:

switch(config-route-map)# match ipv6 address access-list-name ACLv6

match length min max

Example:

switch(config-route-map)# match length 64 1500

Matches against the length of the packet. This command is used for policy-based routing.

match mac-list maclist [...maclist ]

Example:

switch(config-route-map)# match mac-list MacList10

Matches against a list of MAC addresses. This command is used for policy-based routing.

match metric metric-value [+- deviation-number] [...metric-value [+- deviation-number]]

Example:

switch(config-route-map)# match metric 10

Matches against the routing protocol metric. This command is used for policy-based routing.

match vlan vlan-range

Example:

switch(config-route-map)# match vlan 64

Matches against the VLAN ID of the packet. This command is used for policy-based routing.

You can configure the following optional set parameters for route maps in route-map configuration mode:

Command

Purpose

set ip next-hop address1 [address2...] {load-share | peer-address}

Example:

switch(config-route-map)# set ip next-hop 192.0.2.1

Sets the IPv4 next-hop address for policy-based routing. This command uses the first valid next-hop address if multiple addresses are configured.

Use the optional load-share keyword to load balance traffic across a maximum of 16 next-hop addresses.

set ip default next-hop address1 [address2...] {load-share}

Example:

switch(config-route-map)# set ip default next-hop 192.0.2.2

Sets the IPv4 next-hop address for policy-based routing when there is no explicit route to a destination. This command uses the first valid next-hop address if multiple addresses are configured.

Use the optional load-share keyword to load balance traffic across a maximum of 16 next-hop addresses.

set ipv6 next-hop address1 [address2...] {load-share | peer-address}

Example:

switch(config-route-map)# set ipv6 next-hop 2001:0DB8::1

Sets the IPv6 next-hop address for policy-based routing. This command uses the first valid next-hop address if multiple addresses are configured.

Use the optional load-share keyword to load balance traffic across a maximum of 16 next-hop addresses.

set ipv6 default next-hop address1 [address2...]

Example:

switch(config-route-map)# set ipv6 default next-hop 2001:0DB8::2

Sets the IPv6 next-hop address for policy-based routing when there is no explicit route to a destination. This command uses the first valid next-hop address if multiple addresses are configured.

set interface {null0 | tunnel-te)

Example:

switch(config-route-map)# set interface null0

Sets the interface used for routing. Use the null0 interface to drop packets. Use the tunnel-te interface to forward packets on the MPLS TE tunnel.

set vrf vrf-name

Example:

switch(config-route-map)# set vrf MainVRF

Sets the VRF for next-hop resolution.

Cisco NX-OS routes the packet as soon as it finds a next hop and an interface.

Verifying the Policy-Based Routing Configuration

Command

Purpose

show [ip | ipv6] policy [name]

Displays information about an IPv4 or IPv6 policy.

show route-map [name] pbr-statistics

Displays policy statistics.

Use the route-map map-name pbr-statistics to enable policy statistics. Use the clear route-map map-name pbr-statistics to clear these policy statistics

Configuration Examples for Policy-BasedRouting

This example shows how to configure a simple route policy on an interface:

feature pbr

ip access-list pbr-sample

permit tcp host 10.1.1.1 host 192.168.2.1 eq 80

!

route-map pbr-sample

match ip address pbr-sample

set ip next-hop 192.168.1.1

!

route-map pbr-sample pbr-statistics

interface ethernet 1/2

ip policy route-map pbr-sample

The following output verifies this configuration:

n7000# show route-map pbr-sample

route-map pbr-sample, permit, sequence 10

Match clauses:

ip address (access-lists): pbr-sample

Set clauses:

ip next-hop 192.168.1.1

n7000# show route-map pbr-sample pbr-statistics

route-map pbr-sample, permit, sequence 10

Policy routing matches: 84 packets

Default routing: 233 packets

Related Topics

The following topics can give more information on Policy Based Routing:

- Chapter 16, “Configuring Route Policy Manager”

Additional References

For additional information related to implementing IP, see the following sections:

- Related Documents

- Standards

Related Documents

Related Topic

Document Title

Policy-based routing CLI commands

Cisco Nexus 7000 Series NX-OS Unicast Routing Command Reference, Release 5.x

VDCs and VRFs

Cisco Nexus 7000 Series NX-OS Virtual Device Context Configuration Guide, Release 5.x

Standards

Standards

Title

No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.

—

Feature History for Policy-Based Routing

Table 17-2 Feature History for Policy-Based Routing

Feature Name

Releases

Feature Information

Policy-based routing

5.2(4)

Added support for policy-based routing and WCCPv2 on the same interface if bank chaining is disabled.

Interfaces

5.2(1)

Added support for set interface route-map command.

IPv6 policies

4.2(1)

Added support for IPv6 policies.

Policy-based routing

4.0(1)

Configuring RIP

This chapter describes how to configure the Routing Information Protocol (RIP) on the Cisco NX-OS device.

This chapter includes the following sections:

- Information About RIP

- Licensing Requirements for RIP

- Prerequisites for RIP

- Guidelines and Limitations

- Default Settings

- Configuring RIP

- Verifying the RIP Configuration

- Displaying RIP Statistics

- Configuration Examples for RIP

- Related Topics

- Additional References

- Feature History for RIP

Information About RIP

This section includes the following topics:

- RIP Overview

- RIPv2 Authentication

- Split Horizon

- Route Filtering

- Route Summarization

- Route Redistribution

- Load Balancing

- High Availability

- Virtualization Support

RIP Overview

RIP uses User Datagram Protocol (UDP) data packets to exchange routing information in small internetworks. RIPv2 supports IPv4. RIPv2 uses an optional authentication feature supported by the RIPv2 protocol (see the “RIPv2 Authentication” section).

Note Cisco NX-OS does not support IPv6 for RIP.

RIP uses the following two message types:

- Request—Sent to the multicast address 224.0.0.9 to request route updates from other RIP-enabled routers.

- Response—Sent every 30 seconds by default (see the “Verifying the RIP Configuration” section). The router also sends response messages after it receives a Request message. The response message contains the entire RIP route table. RIP sends multiple response packets for a request if the RIP routing table cannot fit in one response packet.

RIP uses a hop count for the routing metric. The hop count is the number of routers that a packet can traverse before reaching its destination. A directly connected network has a metric of 1; an unreachable network has a metric of 16. This small range of metrics makes RIP an unsuitable routing protocol for large networks.

RIPv2 Authentication

You can configure authentication on RIP messages to prevent unauthorized or invalid routing updates in your network. Cisco NX-OS supports a simple password or an MD5 authentication digest.

You can configure the RIP authentication per interface by using key-chain management for the authentication keys. Key-chain management allows you to control changes to the authentication keys used by an MD5 authentication digest or simple text password authentication. See the Cisco Nexus 7000 Series NX-OS Security Configuration Guide, Release 5.x, for more details about creating key-chains.

To use an MD5 authentication digest, you configure a password that is shared at the local router and all remote RIP neighbors. Cisco NX-OS creates an MD5 one-way message digest based on the message itself and the encrypted password and sends this digest with the RIP message (Request or Response). The receiving RIP neighbor validates the digest by using the same encrypted password. If the message has not changed, the calculation is identical and the RIP message is considered valid.

An MD5 authentication digest also includes a sequence number with each RIP message to ensure that no message is replayed in the network.

Split Horizon

You can use split horizon to ensure that RIP never advertises a route out of the interface where it was learned.

Split horizon is a method that controls the sending of RIP update and query packets. When you enable split horizon on an interface, Cisco NX-OS does not send update packets for destinations that were learned from this interface. Controlling update packets in this manner reduces the possibility of routing loops.

You can use split horizon with poison reverse to configure an interface to advertise routes learned by RIP as unreachable over the interface that learned the routes. Figure 12-1 shows a sample RIP network with split horizon and poison reverse enabled.

Figure 12-1 RIP with Split Horizon Poison Reverse

Router C learns about route X and advertises that route to Router B. Router B in turn advertises route X to Router A, but sends a route X unreachable update back to Router C.

By default, split horizon is enabled on all interfaces.

Route Filtering

You can configure a route policy on a RIP-enabled interface to filter the RIP updates. Cisco NX-OS updates the route table with only those routes that the route policy allows.

Route Summarization

You can configure multiple summary aggregate addresses for a specified interface. Route summarization simplifies route tables by replacing a number of more-specific addresses with an address that represents all the specific addresses. For example, you can replace 10.1.1.0/24, 10.1.2.0/24, and 10.1.3.0/24 with one summary address, 10.1.0.0/16.

If more specific routes are in the routing table, RIP advertises the summary address from the interface with a metric equal to the maximum metric of the more specific routes.

Note Cisco NX-OS does not support automatic route summarization.

Route Redistribution

You can use RIP to redistribute static routes or routes from other protocols. You must configure a route map with the redistribution to control which routes are passed into RIP. A route policy allows you to filter routes based on attributes such as the destination, origination protocol, route type, route tag, and so on. For more information, see Chapter16, “Configuring Route Policy Manager”

Whenever you redistribute routes into a RIP routing domain, Cisco NX-OS does not, by default, redistribute the default route into the RIP routing domain. You can generate a default route into RIP, which can be controlled by a route policy.

You also configure the default metric that is used for all imported routes into RIP.

Load Balancing

You can use load balancing to allow a router to distribute traffic over all the router network ports that are the same distance from the destination address. Load balancing increases the usage of network segments and increases effective network bandwidth.

Cisco NX-OS supports the Equal Cost Multiple Paths (ECMP) feature with up to 16 equal-cost paths in the RIP route table and the unicast RIB. You can configure RIP to load balance traffic across some or all of those paths.

High Availability

Cisco NX-OS supports stateless restarts for RIP. After a reboot or supervisor switchover, Cisco NX-OS applies the running configuration and RIP immediately sends request packets to repopulate its routing table.

Virtualization Support

Cisco NX-OS supports multiple instances of the RIP protocol that run on the same system. RIP supports virtual routing and forwarding (VRF) instances. VRFs exist within virtual device contexts (VDCs).

You can configure up to four RIP instances on a VDC. By default, Cisco NX-OS places you in the default VDC and default VRF unless you specifically configure another VDC and VRF. See the Cisco NX-OS Virtual Device Context Configuration Guide and Chapter14, “Configuring Layer 3 Virtualization”

Licensing Requirements for RIP

The following table shows the licensing requirements for this feature:

Product

License Requirement

Cisco NX-OS

RIP requires no license. Any feature not included in a license package is bundled with the Cisco NX-OS system images and is provided at no extra charge to you. For a complete explanation of the Cisco NX-OS licensing scheme, see the Cisco NX-OS Licensing Guide.

Prerequisites for RIP

RIP has the following prerequisites:

- You must enable RIP (see the “Enabling RIP” section).

- If you configure VDCs, install the Advanced Services license and enter the desired VDC (see the Cisco NX-OS Virtual Device Context Configuration Guide).

Guidelines and Limitations

RIP has the following configuration guidelines and limitations:

- Cisco NX-OS does not support RIPv1. If Cisco NX-OS receives a RIPv1 packet, it logs a message and drops the packet.

- Cisco NX-OS does not establish adjacencies with RIPv1 routers.

Default Settings

Table 12-1 lists the default settings for RIP parameters.

Table 12-1 Default RIP Parameters

Parameters

Default

Maximum paths for load balancing

8

RIP feature

Disabled

Split horizon

Enabled

Configuring RIP

This section includes the following topics:

- Enabling RIP

- Creating a RIP Instance

- Configuring RIP on an Interface

- Configuring a Passive Interface

- Configuring Route Summarization

- Configuring Route Summarization

- Configuring Route Redistribution

- Configuring Virtualization

- Tuning RIP

Note If you are familiar with the Cisco IOS CLI, be aware that the Cisco NX-OS commands for this feature might differ from the Cisco IOS commands that you would use.

Enabling RIP

You must enable RIP before you can configure RIP.

BEFORE YOU BEGIN

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. feature rip

3. (Optional) show feature

4. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

feature rip

Example:

switch(config)# feature rip

Enables the RIP feature.

Step 3

show feature

Example:

switch(config)# show feature

(Optional) Displays enabled and disabled features.

Step 4

copy running-config startup-config

Example:

switch(config)# copy running-config startup-config

(Optional) Saves this configuration change.

To disable the RIP feature and remove all associated configurations, use the following command in global configuration mode.

Command

Purpose

no feature rip

Example:

switch(config)# no feature rip

Disables the RIP feature and removes all associated configurations.

Creating a RIP Instance

You can create a RIP instance and configure the address family for that instance.

BEFORE YOU BEGIN

You must enable RIP (see the “Enabling RIP” section).

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. router rip instance-tag

3. address-family ip unicast

4. (Optional) show ip rip [instance instance-tag] [vrf vrf-name]

5. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

router rip instance-tag

Example:

switch(config)# router RIP Enterprise

switch(config-router)#

Creates a new RIP instance with the configured instance-tag.

Step 3

address-family ipv4 unicast

Example:

switch(config-router)# address-family ipv4 unicast

switch(config-router-af)#

Configures the address family for this RIP instance and enters address-family configuration mode.

Step 4

show ip rip [instance instance-tag] [vrf vrf-name]

Example:

switch(config-router-af)# show ip rip

(Optional) Displays a summary of RIP information for all RIP instances.

Step 5

copy running-config startup-config

Example:

switch(config-router-af)# copy running-config startup-config

(Optional) Saves this configuration change.

To remove the RIP instance and the associated configurations, use the following command in global configuration mode.

Command

Purpose

no router rip instance-tag

Example:

switch(config)# no router rip Enterprise

Deletes the RIP instance and all associated configuration.

Note You must also remove any RIP commands configured in interface mode.

You can configure the following optional parameters for RIP in address-family configuration mode:

Command

Purpose

distance value

Example:

switch(config-router-af)# distance 30

Sets the administrative distance for RIP. The range is from 1 to 255. The default is 120. See the “Administrative Distance” section.

maximum-paths number

Example:

switch(config-router-af)# maximum-paths 6

Configures the maximum number of equal-cost paths that RIP maintains in the route table. The range is from 1 to 16.

The following example shows how to create a RIP instance for IPv4 and set the number of equal-cost paths for load balancing:

switch# configure terminal

switch(config)# router rip Enterprise

switch(config-router)# address-family ipv4 unicast

switch(config-router-af)# max-paths 10

switch(config-router-af)# copy running-config startup-config

Restarting a RIP Instance

You can restart a RIP instance. This clears all neighbors for the instance.

To restart an RIP instance and remove all associated neighbors, use the following command:

Command

Purpose

restart rip instance-tag

Example:

switch(config)# restart rip Enterprise

Restarts the RIP instance and removes all neighbors.

Configuring RIP on an Interface

You can add an interface to a RIP instance.

BEFORE YOU BEGIN

You must enable RIP (see the “Enabling RIP” section).

Enter the correct VDC if necessary before configuring RIP.

SUMMARY STEPS

1. configure terminal

2. interface interface-type slot/port

3. ip router rip instance-tag

4. (Optional) show ip rip [instance instance-tag] interface [interface-type slot/port] [vrf vrf-name] [detail]

5. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

interface interface-type slot/port

Example:

switch(config)# interface ethernet 1/2

switch(config-if)#

Enters interface configuration mode.

Step 3

ip router rip instance-tag

Example:

switch(config-if)# ip router rip Enterprise

Associates this interface with a RIP instance.

Step 4

show ip rip [instance instance-tag] interface [interface-type slot/port] [vrf vrf-name] [detail]

Example:

switch(config-if)# show ip rip Enterprise tethernet 1/2

(Optional) Displays RIP information for an interface.

Step 5

copy running-config startup-config

Example:

switch(config-if)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to add Ethernet 1/2 interface to a RIP instance:

switch# configure terminal

switch(config)# interface ethernet 1/2

switch(config-if)# ip router rip Enterprise

switch(config)# copy running-config startup-config

Configuring RIP Authentication

You can configure authentication for RIP packets on an interface.

BEFORE YOU BEGIN

You must enable RIP (see the “Enabling RIP” section).

Ensure that you are in the correct VDC (or use the switchto vdc command).

Configure a key chain if necessary before enabling authentication. See the Cisco Nexus 7000 Series NX-OS Security Configuration Guide, Release 5.x, for details on implementing key chains.

SUMMARY STEPS

1. configure terminal

2. interface interface-type slot/port

3. ip rip authentication mode{text | md5}

4. ip rip authentication keychain key

5. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

interface interface-type slot/port

Example:

switch(config)# interface ethernet 1/2

switch(config-if)#

Enters interface configuration mode.

Step 3

ip rip authentication mode {text | md5}

Example:

switch(config-if)# ip rip authentication mode md5

Sets the authentication type for RIP on this interface as cleartext or MD5 authentication digest.

Step 4

ip rip authentication keychain key

Example:

switch(config-if)# ip rip authentication keychain RIPKey

Configures the authentication key used for RIP on this interface.

Step 5

copy running-config startup-config

Example:

switch(config-if)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to create a key chain and configure MD5 authentication on a RIP interface:

switch# configure terminal

switch(config)# key chain RIPKey

switch(config)# key-string myrip

switch(config)# accept-lifetime 00:00:00 Jan 01 2000 infinite

switch(config)# send-lifetime 00:00:00 Jan 01 2000 infinite

switch(config)# interface ethernet 1/2

switch(config-if)# ip rip authentication mode md5

switch(config-if)# ip rip authentication keychain RIPKey

switch(config-if)# copy running-config startup-config

Configuring a Passive Interface

You can configure a RIP interface to receive routes but not send route updates by setting the interface to passive mode.

To configure a RIP interface in passive mode, use the following command in interface configuration mode:

Command

Purpose

ip rip passive-interface

Example:

switch(config-if)# ip rip passive-interface

Sets the interface into passive mode.

Configuring Split Horizon with Poison Reverse

You can configure an interface to advertise routes learned by RIP as unreachable over the interface that learned the routes by enabling poison reverse.

To configure split horizon with poison reverse on an interface, use the following command in interface configuration mode:

Command

Purpose

ip rip poison-reverse

Example:

switch(config-if)# ip rip poison-reverse

Enables split horizon with poison reverse. Split horizon with poison reverse is disabled by default.

Configuring Route Summarization

You can create aggregate addresses that are represented in the routing table by a summary address. Cisco NX-OS advertises the summary address metric that is the smallest metric of all the more-specific routes.

To configure a summary address on an interface, use the following command in interface configuration mode:

Command

Purpose

ip rip summary-address ip-prefix/mask-len

Example:

switch(config-if)# ip router rip summary-address 192.0.2.0/24

Configures a summary address for RIP for IPv4 addresses.

Configuring Route Redistribution

You can configure RIP to accept routing information from another routing protocol and redistribute that information through the RIP network. Redistributed routes can optionally be assigned a default route.

BEFORE YOU BEGIN

You must enable RIP (see the “Enabling RIP” section).

Enter the correct VDC if necessary before configuring RIP.

Configure a route map before configuring redistribution. See the“Configuring Route Maps” section for details on configuring route maps.

SUMMARY STEPS

1. configure terminal

2. router rip instance-tag

3. address-family ipv4 unicast

4. redistribute {bgp as | direct | eigrp | isis | ospf | ospfv3 | rip} instance-tag | static} route-map map-name

5. (Optional) default-information originate [always] [route-map map-name]

6. (Optional) default-metric value

7. (Optional) show ip rip route [{ip-prefix [longer-prefixes | shorter-prefixes]] [vrf vrf-name] [summary]

8. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

router rip instance-tag

Example:

switch(config)# router rip Enterprise

switch(config-router)#

Creates a new RIP instance with the configured instance-tag.

Step 3

address-family ipv4 unicast

Example:

switch(config-router)# address-family ipv4 unicast

switch(config-router-af)#

Enters address family configuration mode.

Step 4

redistribute {bgp as | direct |{eigrp | isis | ospf | ospfv3 | rip} instance-tag | static} route-map map-name

Example:

switch(config-router-af)# redistribute eigrp 201 route-map RIPmap

Redistributes routes from other protocols into RIP. See the “Configuring Route Maps” section for more information about route maps.

Step 5

default-information originate [always] [route-map map-name]

Example:

switch(config-router-af)# default-information originate always

(Optional) Generates a default route into RIP, optionally controlled by a route map.

Step 6

default-metric value

Example:

switch(config-router-af)# distribute level-1 into level-2 all

(Optional) Sets the default metric for all redistributed routes. The range is from 1 to 15. The default is 1.

Step 7

show ip rip route [ip-prefix [longer-prefixes | shorter-prefixes] [vrf vrf-name] [summary]

Example:

switch(config-router-af)# show ip rip route

(Optional) Shows the routes in RIP.

Step 8

copy running-config startup-config

Example:

switch(config-router-af)# copy running-config startup-config

(Optional) Saves this configuration change.

The following example shows how to redistribute EIGRP into RIP:

switch# configure terminal

switch(config)# router rip Enterprise

switch(config-router)# address-family ipv4 unicast

switch(config-router-af)# redistribute eigrp 201 route-map RIPmap

switch(config-router-af)# copy running-config startup-config

Configuring Virtualization

You can configure multiple RIP instances in each VDC. You can also create multiple VRFs within each VDC and use the same or multiple RIP instances in each VRF. You assign a RIP interface to a VRF.

Note Configure all other parameters for an interface after you configure the VRF for an interface. Configuring a VRF for an interface deletes all the configurations for that interface.

BEFORE YOU BEGIN

You must enable RIP (see the “Enabling RIP” section).

Create the VDCs.

SUMMARY STEPS

1. configure terminal

2. vrf context vrf_name

3. exit

4. router rip instance-tag

5. vrf vrf-name

6. (Optional) address-family ipv4 unicast

7. (Optional) redistribute {bgp as | direct | {eigrp | isis | ospf | ospfv3 | rip} instance-tag | static} route-map map-name

8. interface ethernet slot/port

9. vrf member vrf-name

10. ip-address ip-prefix/length

11. ip router rip instance-tag

12. (Optional) show ip rip [instance instance-tag] interface [interface-type slot/port] [vrf vrf-name]

13. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

vrf vrf-name

Example:

switch(config)# vrf RemoteOfficeVRF

switch(config-vrf)#

Creates a new VRF.

Step 3

exit

Example:

switch(config-vrf)# exit

switch(config)#

Exits VRF configuration mode.

Step 4

router rip instance-tag

Example:

switch(config)# router rip Enterprise

switch(config-router)#

Creates a new RIP instance with the configured instance tag.

Step 5

vrf context vrf-name

Example:

switch(config)# vrf context RemoteOfficeVRF

switch(config-vrf)#

Creates a new VRF and enters VRF configuration mode.

Step 6

address-family ipv4 unicast

Example:

switch(config-router-vrf)# address-family ipv4 unicast

switch(config-router-vrf-af)#

(Optional) Configures the VRF address family for this RIP instance.

Step 7

redistribute {bgp as | direct | {eigrp | isis | ospf | ospfv3 | rip} instance-tag | static} route-map map-name

Example:

switch(config-router-vrf-af)# redistribute eigrp 201 route-map RIPmap

(Optional) Redistributes routes from other protocols into RIP. See the “Configuring Route Maps” section for more information about route maps.

Step 8

interface ethernet slot/port

Example:

switch(config-router-vrf-af)# interface ethernet 1/2

switch(config-if)#

Enters interface configuration mode.

Step 9

vrf member vrf-name

Example:

switch(config-if)# vrf member RemoteOfficeVRF

Adds this interface to a VRF.

Step 10

ip address ip-prefix/length

Example:

switch(config-if)# ip address 192.0.2.1/16

Configures an IP address for this interface. You must do this step after you assign this interface to a VRF.

Step 11

ip router rip instance-tag

Example:

switch(config-if)# ip router rip Enterprise

Associates this interface with a RIP instance.

Step 12

show ip rip [instance instance-tag] interface [interface-type slot/port] [vrf vrf-name]

Example:

switch(config-if)# show ip rip Enterprise ethernet 1/2

(Optional) Displays RIP information for an interface. in a VRF.

Step 13

copy running-config startup-config

Example:

switch(config-if)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to create a VRF and add an interface to the VRF:

switch# configure terminal

switch(config)# vrf context RemoteOfficeVRF

switch(config-vrf)# exit

switch(config)# router rip Enterprise

switch(config-router)# vrf RemoteOfficeVRF

switch(config-router-vrf)# address-family ipv4 unicast

switch(config-router-vrf-af)# redistribute eigrp 201 route-map RIPmap

switch(config-router-vrf-af)# interface ethernet 1/2

switch(config-if)# vrf member RemoteOfficeVRF

switch(config-if)# ip address 192.0.2.1/16

switch(config-if)# ip router rip Enterprise

switch(config-if)# copy running-config startup-config

Tuning RIP

You can tune RIP to match your network requirements. RIP uses several timers that determine the frequency of routing updates, the length of time before a route becomes invalid, and other parameters. You can adjust these timers to tune routing protocol performance to better suit your internetwork needs.

Note You must configure the same values for the RIP timers on all RIP-enabled routers in your network.

You can use the following optional commands in address-family configuration mode to tune RIP:

Command

Purpose

timers basic update timeout holddown garbage-collection

Example:

switch(config-router-af)# timers basic 40 120 120 100

Sets the RIP timers in seconds. The parameters are as follows:

- update—The range is from 5 to any positive integer. The default is 30.

- timeout—The time that Cisco NX-OS waits before declaring a route as invalid. If Cisco NX-OS does not receive route update information for this route before the timeout interval ends, Cisco NX-OS declares the route as invalid. The range is from 1 to any positive integer. The default is 180.

- holddown—The time during which Cisco NX-OS ignores better route information for an invalid route. The range is from 0 to any positive integer. The default is 180.

- garbage-collection—The time from when Cisco NX-OS marks a route as invalid until Cisco NX-OS removes the route from the routing table. The range is from 1 to any positive integer. The default is 120.

You can use the following optional commands in interface configuration mode to tune RIP:

Command

Purpose

ip rip metric-offset value

Example:

switch(config-if)# ip rip metric-offset 10

Adds a value to the metric for every router received on this interface. The range is from 1 to 15. The default is 1.

ip rip route-filter {prefix-list list-name | route-map map-name| [in | out]

Example:

switch(config-if)# ip rip route-filter route-map InputMap in

Specifies a route map to filter incoming or outgoing RIP updates.

Verifying the RIP Configuration

To display RIP configuration, perform one of the following tasks:

Command

Purpose

show ip rip instance [instance-tag] [vrf vrf-name]

Displays the status for an instance of RIP.

show ip rip [instance instance-tag] interface slot/port detail [vrf vrf-name]

Displays the RIP status for an interface.

show ip rip [instance instance-tag] neighbor [interface-type number] [vrf vrf-name]

Displays the RIP neighbor table.

show ip} rip [instance instance-tag] route [ip-prefix/lengh [longer-prefixes | shorter--prefixes]] [summary] [vrf vrf-name]

Displays the RIP route table.

show running-configuration rip

Displays the current running RIP configuration.

Displaying RIP Statistics

To display RIP statistics, use the following commands:

Command

Purpose

show ip rip [instance instance-tag] policy statistics redistribute {bgp as | direct | {eigrp | isis | ospf | ospfv3 | rip} instance-tag | static} [vrf vrf-name]

Displays the RIP policy status.

show ip rip [instance instance-tag] statistics interface-type number] [vrf vrf-name]

Displays the RIP statistics.

Use the clear ip rip policy command to clear policy statistics.

Use the clear ip rip statistics command to clear RIP statistics.

Configuration Examples for RIP

This example creates the Enterprise RIP instance in a VRF and adds Ethernet interface 1/2 to this RIP instance. The example also configures authentication for Ethernet interface 1/2 and redistributes EIGRP into this RIP domain.

vrf context NewVRF

!

feature rip

router rip Enterprise

vrf NewVRF

address-family ip unicast

redistribute eigrp 201 route-map RIPmap

max-paths 10

!

interface ethernet 1/2

vrf NewVRF

ip address 192.0.2.1/16

ip router rip Enterprise

ip rip authentication mode md5

ip rip authentication keychain RIPKey

Related Topics

See Chapter 16, “Configuring Route Policy Manager” for more information on route maps.

Additional References

For additional information related to implementing RIP, see the following sections:

- Related Documents

- Standards

Related Documents

Related Topic

Document Title

RIP CLI commands

Cisco Nexus 7000 Series NX-OS Unicast Routing Command Reference, Release 5.x

VDCs and VRFs

Cisco Nexus 7000 Series NX-OS Virtual Device Context Configuration Guide, Release 5.x

Standards

Standards

Title

No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.

—

Feature History for RIP

Table 12-2 lists the release history for this feature.

Table 12-2 Feature History for RIP

Feature Name

Releases

Feature Information

RIP

4.0(1)

This feature was introduced.

Configuring Static Routing

This chapter describes how to configure static routing on the Cisco NX-OS device.

This chapter includes the following sections:

- Information About Static Routing

- Licensing Requirements for Static Routing

- Prerequisites for Static Routing

- Guidelines and Limitations for Static Routing

- Default Settings

- Configuring Static Routing

- Verifying the Static Routing Configuration

- Configuration Examples for Static Routing

- Additional References

- Feature History for Static Routing

Information About Static Routing

Routers forward packets using either route information from route table entries that you manually configure or the route information that is calculated using dynamic routing algorithms.

Static routes, which define explicit paths between two routers, cannot be automatically updated; you must manually reconfigure static routes when network changes occur. Static routes use less bandwidth than dynamic routes. No CPU cycles are used to calculate and analyze routing updates.

You can supplement dynamic routes with static routes where appropriate. You can redistribute static routes into dynamic routing algorithms but you cannot redistribute routing information calculated by dynamic routing algorithms into the static routing table.

You should use static routes in environments where network traffic is predictable and where the network design is simple. You should not use static routes in large, constantly changing networks because static routes cannot react to network changes. Most networks use dynamic routes to communicate between routers but might have one or two static routes configured for special cases. Static routes are also useful for specifying a gateway of last resort (a default router to which all unroutable packets are sent).

This section includes the following topics:

- Administrative Distance

- Directly Connected Static Routes

- Fully Specified Static Routes

- Floating Static Routes

- Remote Next Hops for Static Routes

- BFD

- Virtualization Support

Administrative Distance

An administrative distance is the metric used by routers to choose the best path when there are two or more routes to the same destination from two different routing protocols. An administrative distance guides the selection of one routing protocol (or static route) over another, when more than one protocol adds the same route to the unicast routing table. Each routing protocol is prioritized in order of most to least reliable using an administrative distance value.

Static routes have a default administrative distance of 1. A router prefers a static route to a dynamic route because the router considers a route with a low number to be the shortest. If you want a dynamic route to override a static route, you can specify an administrative distance for the static route. For example, if you have two dynamic routes with an administrative distance of 120, you would specify an administrative distance that is greater than 120 for the static route if you want the dynamic route to override the static route.

Directly Connected Static Routes

You must specify only the output interface (the interface on which all packets are sent to the destination network) in a directly connected static route. The router assumes the destination is directly attached to the output interface and the packet destination is used as the next-hop address. The next hop can be an interface, only for point-to-point interfaces. For broadcast interfaces, the next hop must be an IPv4/IPv6 address.

Fully Specified Static Routes

You must specify either the output interface (the interface on which all packets are sent to the destination network) or the next-hop address in a fully specified static route. You can use a fully specified static route when the output interface is a multi-access interface and you need to identify the next-hop address. The next-hop address must be directly attached to the specified output interface.

Floating Static Routes

A floating static route is a static route that the router uses to back up a dynamic route. You must configure a floating static route with a higher administrative distance than the dynamic route that it backs up. In this instance, the router prefers a dynamic route to a floating static route. You can use a floating static route as a replacement if the dynamic route is lost.

Note By default, a router prefers a static route to a dynamic route because a static route has a smaller administrative distance than a dynamic route.

Remote Next Hops for Static Routes

You can specify the next-hop address of a neighboring router that is not directly connected to the router for static routes with remote (nondirectly attached) next-hops. If a static route has remote next hops during data forwarding, the next hops are recursively used in the unicast routing table to identify the corresponding directly attached next hops that have reachability to the remote next hops.

BFD

This feature supports bidirectional forwarding detection (BFD). BFD is a detection protocol designed to provide fast forwarding-path failure detection times. BFD provides subsecond failure detection between two adjacent devices and can be less CPU-intensive than protocol hello messages because some of the BFD load can be distributed onto the data plane on supported modules. See the Cisco Nexus 7000 Series NX-OS Interfaces Configuration Guide, Release 5.x, for more information.

Virtualization Support

Static routes support virtual routing and forwarding (VRF) instances. VRFs exist within virtual device contexts (VDCs). By default, Cisco NX-OS places you in the default VDC and default VRF unless you specifically configure another VDC and VRF. For more information, see the Cisco Nexus 7000 Series NX-OS Virtual Device Context Configuration Guide, Release 5.x, and Chapter14, “Configuring Layer 3 Virtualization”

Licensing Requirements for Static Routing

The following table shows the licensing requirements for this feature:

Product

License Requirement

Cisco NX-OS

Static routing requires no license. Any feature not included in a license package is bundled with the Cisco NX-OS system images and is provided at no extra charge to you. For a complete explanation of the Cisco NX-OS licensing scheme, see the Cisco NX-OS Licensing Guide.

Prerequisites for Static Routing

Static routing has the following prerequisites:

- If the next-hop address for a static route is unreachable, the static route is not added to the unicast routing table.

Guidelines and Limitations for Static Routing

Static routing has the following configuration guidelines and limitations:

- You can specify an interface as the next-hop address for a static route only for point-to-point interfaces such as generic routing encapsulation (GRE) tunnels.

Default Settings

Table 13-1 Default Static Routing Parameters

Parameters

Default

administrative distance

1

RIP feature

Disabled

Configuring Static Routing

This section includes the following topics:

- Configuring a Static Route

- Configuring Virtualization

- Verifying the Static Routing Configuration

Note If you are familiar with the Cisco IOS CLI, be aware that the Cisco NX-OS commands for this feature might differ from the Cisco IOS commands that you would use.

Configuring a Static Route

You can configure a static route on the router.

BEFORE YOU BEGIN

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. ip route {ip-prefix | ip-addr/ip-mask} {[next-hop | nh-prefix] | [interface next-hop | nh-prefix]} [name nexthop-name] [tag tag-value] [pref]

or

ipv6 route ip6-prefix {nh-prefix | link-local-nh-prefix} | {nh-prefix [interface] | link-local-nh-prefix [interface]} [name nexthop-name] [tag tag-value] [pref]

3. (Optional) show {ip | ipv6} static-route

4. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

ip route {ip-prefix | ip-addr/ip-mask} {[next-hop | nh-prefix] | [interface next-hop | nh-prefix]} [name nexthop-name] [tag tag-value] [pref]

Example:

switch(config)# ip route 192.0.2.0/8 ethernet 1/2 192.0.2.4

Configures a static route and the interface for this static route. Use ? to display a list of supported interfaces. You can specify a null interface by using null 0.

You can optionally configure the next-hop address.

The preference value sets the administrative distance. The range is from 1 to 255. The default is 1.

ipv6 route ip6-prefix {nh-prefix|link-local-nh-prefix} | (nexthop [interface] | link-local-nexthop [interface]} [name nexthop-name] [tag tag-value] [pref]

Example:

switch(config)# ipv6 route 2001:0DB8::/48 6::6 ethernet 2/1

Configures a static route and the interface for this static route. Use ? to display a list of supported interfaces. You can specify a null interface by using null 0.

You can optionally configure the next-hop address.

The preference value sets the administrative distance. The range is from 1 to 255. The default is 1.

Step 3

show {ip | ipv6} static-route

Example:

switch(config)# show ip static-route

(Optional) Displays information about static routes.

Step 4

copy running-config startup-config

Example:

switch(config)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to configure a static route for a null interface:

switch# configure terminal

switch(config)# ip route 1.1.1.1/32 null 0

switch(config)# copy running-config startup-config

Use the no {ip | ipv6} static-route command to remove the static route.

Configuring Virtualization

You can configure a static route in a VRF.

BEFORE YOU BEGIN

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. vrf context vrf-name

3. ip route {ip-prefix | ip-addr ip-mask} {next-hop | nh-prefix | interface} [name nexthop-name] [tag tag-value] [pref]

or

ipv6 route ip6-prefix {nh-prefix | link-local-nh-prefix} | {next-hop [interface] | link-local-next-hop [interface]} [name nexthop-name] [tag tag-value] [pref]

4. (Optional) show {ip | ipv6} static-route vrf vrf-name

5. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

vrf context vrf-name

Example:

switch(config)# vrf context StaticVrf

Creates a VRF and enters VRF configuration mode.

Step 3

ip route {ip-prefix | ip-addr ip-mask} {next-hop | nh-prefix | interface} [name nexthop-name] [tag tag-value] [pref]

Example:

switch(config-vrf)# ip route 192.0.2.0/8 ethernet 1/2

Configures a static route and the interface for this static route. Use ? to display a list of supported interfaces. You can specify a null interface by using null 0.

You can optionally configure the next-hop address.

The preference value sets the administrative distance. The range is from 1 to 255. The default is 1.

ipv6 route ip6-prefix {nh-prefix|link-local-nh-prefix} | (nexthop [interface] | link-local-nexthop [interface]} [name nexthop-name] [tag tag-value] [pref]

Example:

switch(config)# ipv6 route 2001:0DB8::/48 6::6 ethernet 2/1

Configures a static route and the interface for this static route. Use ? to display a list of supported interfaces. You can specify a null interface by using null 0.

You can optionally configure the next-hop address.

The preference value sets the administrative distance. The range is from 1 to 255. The default is 1.

Step 4

show {ip | ipv6} static-route vrf vrf-name

Example:

switch(config-vrf)# show ip static-route

(Optional) Displays information on static routes.

Step 5

copy running-config startup-config

Example:

switch(config-vrf)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to configure a static route:

switch# configure terminal

switch(config)# vrf context StaticVrf

switch(config-vrf)# ip route 192.0.2.0/8 192.0.2.10

switch(config-vrf)# copy running-config startup-config

Configuring Layer 3 Routing Using a Mixed Chassis

A mixed chassis is a Cisco Nexus 7000 Series chassis that contains at least one M-Series module and at least one N7K-F132-15 module. Because the N7K-F132-15 module processes only Layer 2 traffic, you must use this configuration to pass Layer 3 traffic through the chassis.

Note This is an optional procedure.

To configure a Layer 3 gateway in a mixed chassis, you use the proxy routing functionality. You enable routing on a specific VLAN by configuring a VLAN interface and the system automatically provides load-balanced routing functionality. (See the Cisco Nexus 7000 Series NX-OS Interfaces Configuration Guide, Release 5.x, for more information about Layer 3 routing and VLAN interfaces.)

Optionally, you can specify which physical interfaces on the N7K-M Series modules you want to use for Layer 3 routing.

BEFORE YOU BEGIN

You must configure a VLAN interface for each VLAN on the N7K-F132-15 module that you want to use the proxy-routing functionality in a mixed chassis.

You must have interfaces from both the M Series and the N7K-F132-15 modules in the same VDC.

SUMMARY STEPS

1. configure terminal

2. (Optional) hardware proxy layer-3 routing {use | exclude} {module mod-number | interface slot/port} [module-type f1]

3. exit

4. (Optional) show hardware proxy layer-3 detail

5. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters global configuration mode.

Step 2

hardware proxy layer-3 routing {use | exclude} {module mod-number | interface slot/port} [module-type f1]

Example:

switch(config)# hardware proxy layer-3 forwarding use module 1, 2-6,7

(Optional) Configures specific modules and physical interfaces on the N7K-M Series module to provide the proxy routing on the N7K-F132-15 module.

Step 3

exit

Example:

switch(config)# exit

switch#

Exits configuration mode.

Step 4

show hardware proxy layer-3 detail

Example:

switch# show hardware proxy layer-3 detail

(Optional) Displays the information about the proxy Layer 3 functionality.

Step 5

copy running-config startup-config

Example:

switch# copy running-config startup-config

(Optional) Copies the running configuration to the startup configuration.

This example shows how to specify certain physical interfaces on the N7K-M Series modules to perform proxy routing on the N7K-F132-15 module in a mixed chassis:

switch# configure terminal

switch(config)# hardware proxy later-3 routing use module 1, 2-6, 7

switch(config)#

switch(config)#

Verifying the Static Routing Configuration

Command

Purpose

show ip static-route

Displays the configured static routes.

show ipv6 static-route vrf vrf-name

Displays static route information for each VRF.

show ipv6 static-route

Displays the configured static routes.

show hardware proxy layer-3 detail

Displays information on the proxy routing from an N7K-F132-15 module to the M Series module in the chassis that contains both types of modules.

show hardware proxy layer-3 counters {brief | detail}

Displays the number of packets sent by the N7K-F132-15 modules to each M Series module for proxy forwarding.
command to clear the counters.

Configuration Examples for Static Routing

This example shows how to configure static routing:

configure terminal

ip route 192.0.2.0/8 192.0.2.10

copy running-config startup-config

switch# configure terminal

switch(config)# hardware proxy later-3 forwarding use module 1, 2-6, 7

switch(config)# show hardware proxy layer-3 detail

Additional References

For additional information related to implementing static routing, see the following sections:

- Related Documents

Related Documents

Related Topic

Document Title

Static Routing CLI

Cisco Nexus 7000 Series NX-OS Unicast Routing Command Reference, Release 5.x

VDCs

Cisco Nexus 7000 Series NX-OS Virtual Device Context Configuration Guide, Release 5.x

Feature History for Static Routing

Table 13-2 lists the release history for this feature.

Table 13-2 Feature History for Static Routing

Feature Name

Releases

Feature Information

Layer 3 routing using a mixed chassis

5.1(1)

This feature was introduced.

Static routing

5.1(1)

Added the name option to the ip route command.

BFD

5.0(2)

Added support for BFD. See the Cisco Nexus 7000 Series NX-OS Interfaces Configuration Guide, Release 5.x, for more information.

Static routing

4.0(1)

Configuring Route Policy Manager

This chapter describes how to configure the Route Policy Manager on the Cisco NX-OS device.

This chapter includes the following sections:

- Information About Route Policy Manager

- Licensing Requirements for Route Policy Manager

- Prerequisites for Route Policy Manager

- Guidelines and Limitations

- Default Settings

- Configuring Route Policy Manager

- Verifying the Route Policy Manager Configuration

- Configuration Examples for Route Policy Manager

- Related Topics

- Additional References

- Feature History for Route Policy Manager

Information About Route Policy Manager

Route Policy Manager supports route maps and IP prefix lists. These features are used for route redistribution and policy-based routing. A prefix list contains one or more IPv4 or IPv6 network prefixes and the associated prefix length values. You can use a prefix list by itself in features such as Border Gateway Protocol (BGP) templates, route filtering, or redistribution of routes that are exchanged between routing domains.

Route maps can apply to both routes and IP packets. Route filtering and redistribution pass a route through a route map while policy based routing passes IP packets through a route map.

This section includes the following topics:

- Prefix Lists

- MAC Lists

- Route Maps

- Route Redistribution and Route Maps

- Policy-Based Routing

Prefix Lists

You can use prefix lists to permit or deny an address or range of addresses. Filtering by a prefix list involves matching the prefixes of routes or packets with the prefixes listed in the prefix list. An implicit deny is assumed if a given prefix does not match any entries in a prefix list.

You can configure multiple entries in a prefix list and permit or deny the prefixes that match the entry. Each entry has an associated sequence number that you can configure. If you do not configure a sequence number, Cisco NX-OS assigns a sequence number automatically. Cisco NX-OS evaluates prefix lists starting with the lowest sequence number. Cisco NX-OS processes the first successful match for a given prefix. Once a match occurs, Cisco NX-OS processes the permit or deny statement and does not evaluate the rest of the prefix list.

Note An empty prefix list permits all routes.

MAC Lists

You can use MAC lists to permit or deny a MAC address or range of addresses. A MAC list consists of a list of MAC addresses and optional MAC masks. A MAC mask is a wild-card mask that is logically AND-ed with the MAC address when the route map matches on the MAC list entry. Filtering by a MAC list involves matching the MAC address of packets with the MAC addresses listed in the MAC list. An implicit deny is assumed if a given MAC address does not match any entries in a MAC list.

You can configure multiple entries in a MAC list and permit or deny the MAC addresses that match the entry. Each entry has an associated sequence number that you can configure. If you do not configure a sequence number, Cisco NX-OS assigns a sequence number automatically. Cisco NX-OS evaluates MAC lists starting with the lowest sequence number. Cisco NX-OS processes the first successful match for a given MAC address. Once a match occurs, Cisco NX-OS processes the permit or deny statement and does not evaluate the rest of the MAC list.

Route Maps

You can use route maps for route redistribution or policy-based routing. Route map entries consist of a list of match and set criteria. The match criteria specify match conditions for incoming routes or packets, and the set criteria specify the action taken if the match criteria are met.

You can configure multiple entries in the same route map. These entries contain the same route map name and are differentiated by a sequence number.

You create a route map with one or more route map entries arranged by the sequence number under a unique route map name. The route map entry has the following parameters:

- Sequence number

- Permission—permit or deny

- Match criteria

- Set changes

By default, a route map processes routes or IP packets in a linear fashion, that is, starting from the lowest sequence number. You can configure the route map to process in a different order using the continue statement, which allows you to determine which route map entry to process next.

Match Criteria

You can use a variety of criteria to match a route or IP packet in a route map. Some criteria, such as BGP community lists, are applicable only to a specific routing protocol, while other criteria, such as the IP source or the destination address, can be used for any route or IP packet.

When Cisco NX-OS processes a route or packet through a route map, it compares the route or packet to each of the match statements configured. If the route or packet matches the configured criteria, Cisco NX-OS processes it based on the permit or deny configuration for that match entry in the route map and any set criteria configured.

The match categories and parameters are as follows:

- IP access lists—(For policy-based routing only). Match based on source or destination IP address, protocol, or QoS parameters.

- BGP parameters—Match based on AS numbers, AS-path, community attributes, or extended community attributes.

- Prefix lists—Match based on an address or range of addresses.

- Multicast parameters—Match based on rendezvous point, groups, or sources.

- Other parameters—Match based on IP next-hop address or packet length.

Set Changes

Once a route or packet matches an entry in a route map, the route or packet can be changed based on one or more configured set statements.

The set changes are as follows:

- BGP parameters—Change the AS-path, tag, community, extended community, dampening, local preference, origin, or weight attributes.

- Metrics—Change the route-metric, the route-tag, or the route-type.

- Policy-based routing only—Change the interface or the default next-hop address.

- Other parameters—Change the forwarding address or the IP next-hop address.

Access Lists

IP access lists can match the packet to a number of IP packet fields such as the following:

- Source or destination IPv4 or IPv6 address

- Protocol

- Precedence

- ToS

You can use ACLs in a route map for policy-based routing only. See the Cisco Nexus 7000 Series NX-OS Security Configuration Guide, Release 5.x, for more information on ACLs.

AS Numbers for BGP

You can configure a list of AS numbers to match against BGP peers. If a BGP peer matches an AS number in the list and matches the other BGP peer configuration, BGP creates a session. If the BGP peer does not match an AS number in the list, BGP ignores the peer. You can configure the AS numbers as a list, a range of AS numbers, or you can use an AS-path list to compare the AS numbers against a regular expression.

AS-path Lists for BGP

You can configure an AS-path list to filter inbound or outbound BGP route updates. If the route update contains an AS-path attribute that matches an entry in the AS-path list, the router processes the route based on the permit or deny condition configured. You can configure AS-path lists within a route map.

You can configure multiple AS-path entries in an AS-path list by using the same AS-path list name. The router processes the first entry that matches.

Community Lists for BGP

You can filter BGP route updates based on the BGP community attribute by using community lists in a route map. You can match the community attribute based on a community list, and you can set the community attribute using a route map.

A community list contains one or more community attributes. If you configure more than one community attribute in the same community list entry, the BGP route must match all community attributes listed to be considered a match.

You can also configure multiple community attributes as individual entries in the community list by using the same community list name. In this case, the router processes the first community attribute that matches the BGP route, using the permit or deny configuration for that entry.

You can configure community attributes in the community list in one of the following formats:

- A named community attribute, such as internet or no-export.

- In aa:nn format, where the first two bytes represent the two-byte AS number and the last two bytes represent a user-defined network number.

- A regular expression.

See the Cisco Nexus 7000 Series NX-OS Unicast Routing Command Reference, Release 5.x, for more information on regular expressions.

Extended Community Lists for BGP

Extended community lists support 4-byte AS numbers. You can configure community attributes in the extended community list in one of the following formats:

- In aa4:nn format, where the first four bytes represent the four-byte AS number and the last two bytes represent a a user-defined network number.

- A regular expression.

See the Cisco Nexus 7000 Series NX-OS Unicast Routing Command Reference, Release 5.x, for more information on regular expressions.

Cisco NX-OS supports generic specific extended community lists, which provide similar functionality to regular community lists for four-byte AS numbers. You can configure generic specific extended community lists with the following properties:

- Transitive—BGP propagates the community attributes across autonomous systems.

- Nontransitive—BGP removes community attributes before propagating the route to another autonomous system.

Route Redistribution and Route Maps

You can use route maps to control the redistribution of routes between routing domains. Route maps match on the attributes of the routes to redistribute only those routes that pass the match criteria. The route map can also modify the route attributes during this redistribution using the set changes.

The router matches redistributed routes against each route map entry. If there are multiple match statements, the route must pass all of the match criteria. If a route passes the match criteria defined in a route map entry, the actions defined in the entry are executed. If the route does not match the criteria, the router compares the route against subsequent route map entries. Route processing continues until a match is made or the route is processed by all entries in the route map with no match. If the router processes the route against all entries in a route map with no match, the router accepts the route (inbound route maps) or forwards the route (outbound route maps).

Note When you redistribute BGP to IGP, iBGP is redistributed as well. To override this behavior, you must insert an additional deny statement into the route map.

Policy-Based Routing

You can use policy-based routing to forward a packet to a specified next-hop address based on the source of the packet or other fields in the packet header. For more information, see Chapter17, “Configuring Policy-Based Routing”

Licensing Requirements for Route Policy Manager

The following table shows the licensing requirements for this feature:

Product

License Requirement

Cisco NX-OS

Route Policy Manager requires no license. Any feature not included in a license package is bundled with the Cisco NX-OS system images and is provided at no extra charge to you. For a complete explanation of the Cisco NX-OS licensing scheme, see the Cisco NX-OS Licensing Guide.

Prerequisites for Route Policy Manager

Route Policy Manager has the following prerequisites:

- If you configure VDCs, install the Advanced Services license and enter the desired VDC (see the Cisco NX-OS Virtual Device Context Configuration Guide).

Guidelines and Limitations

Route Policy Manager has the following configuration guidelines and limitations:

- An empty route map denies all the routes.

- An empty prefix list permits all the routes.

- Without any match statement in a route-map entry, the permission (permit or deny) of the route-map entry decides the result for all the routes or packets.

- If referred policies (for example, prefix lists) within a match statement of a route-map entry return either a no-match or a deny-match, Cisco NX-OS fails the match statement and processes the next route-map entry.

- When you change a route map, Cisco NX-OS holds all the changes until you exit from the route-map configuration submode. Cisco NX-OS then sends all the changes to the protocol clients to take effect.

- Because you can use a route map before you define it, verify that all your route maps exist when you finish a configuration change.

- You can view the route-map usage for redistribution and filtering. Each individual routing protocol provides a way to display these statistics.

- When you redistribute BGP to IGP, iBGP is redistributed as well. To override this behavior, you must insert an additional deny statement into the route map.

Default Settings

Table 16-1 Default Route Policy Manager Parameters

Parameters

Default

Route Policy Manager

Enabled

Configuring Route Policy Manager

This section includes the following topics:

- Configuring IP Prefix Lists

- Configuring AS-path Lists

- Configuring Community Lists

- Configuring Extended Community Lists

- Configuring Route Maps

Note If you are familiar with the Cisco IOS CLI, be aware that the Cisco NX-OS commands for this feature might differ from the Cisco IOS commands that you would use.

Configuring IP Prefix Lists

IP prefix lists match the IP packet or route against a list of prefixes and prefix lengths. You can create an IP prefix list for IPv4 and create an IPv6 prefix list for IPv6.

You can configure the prefix list entry to match the prefix length exactly or to match any prefix with a length that matches the configured range of prefix lengths.

Use the ge and lt keywords to create a range of possible prefix lengths. The incoming packet or route matches the prefix list if the prefix matches and if the prefix length is greater than or equal to the ge keyword value (if configured) and less than or equal to the lt keyword value (if configured).

SUMMARY STEPS

1. configure terminal

2. {ip | ipv6} prefix-list name description string

3. ip prefix-list name [seq number] [{permit | deny} prefix {[eq prefix-length] | [ge prefix-length] [le prefix-length]}]

or

ipv6 prefix-list name [seq number] [{permit | deny} prefix {[eq prefix-length] | [ge prefix-length] [le prefix-length]}]

4. (Optional) show {ip | ipv6} prefix-list name

5. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

{ip | ipv6} prefix-list name description string

Example:

switch(config)# ip prefix-list AllowPrefix description allows engineering server

(Optional) Adds an information string about the prefix list.

Step 3

ip prefix-list name [seq number] [{permit | deny} prefix {[eq prefix-length] | [ge prefix-length] [le prefix-length]}]

Example:

switch(config)# ip prefix-list AllowPrefix seq 10 permit 192.0.2.0/24 eq 24

Creates an IPv4 prefix list or adds a prefix to an existing prefix list. The prefix length is matched as follows:

- eq—Matches the exact prefix length .

- ge—Matches a prefix length that is equal to or greater than the configured prefix length .

- le—Matches a prefix length that is equal to or less than the configured prefix length .

ipv6 prefix-list name [seq number] [{permit | deny} prefix {[eq prefix-length] | [ge prefix-length] [le prefix-length]}]

Example:

switch(config)# ipv6 prefix-list AllowIPv6Prefix seq 10 permit 2001:0DB8:: le 32

Creates an IPv6 prefix list or adds a prefix to an existing prefix list. The prefix length is configured as follows:

- eq—Matches the exact prefix length .

- ge—Matches a prefix length that is equal to or greater than the configured prefix length .

- le—Matches a prefix length that is equal to or less than the configured prefix length .

Step 4

show {ip | ipv6} prefix-list name

Example:

switch(config)# show ip prefix-list AllowPrefix

(Optional) Displays information about prefix lists.

Step 5

copy running-config startup-config

Example:

switch# copy running-config startup-config

(Optional) Saves this configuration change.

The following example shows how to create an IPv4 prefix list with two entries and apply the prefix list to a BGP neighbor:

switch# configure terminal

switch(config)# ip prefix-list allowprefix seq 10 permit 192.0.2.0/24 eq 24

switch(config)# ip prefix-list allowprefix seq 20 permit 209.165.201.0/27 eq 27

switch(config)# router bgp 65536:20

switch(config-router)# neighbor 192.0.2.1/16 remote-as 65535:20

switch(config-router-neighbor)# address-family ipv4 unicast

switch(config-router-neighbor-af)# prefix-list allowprefix in

Configuring MAC Lists

You can configure a MAC list to permit or deny a range of MAC addresses.

SUMMARY STEPS

1. configure terminal

2. mac-list name [seq number] {permit | deny} mac-address [mac-mask]

3. (Optional) show mac-list name

4. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

mac-list name [seq number] {permit | deny} mac-address [mac-mask]

Example:

switch(config)# mac-list AllowMac seq 1 permit 0022.5579.a4c1 ffff.ffff.0000

Creates a MAC list or adds a MAC address to an existing MAC list. The seq range is from 1 to 4294967294. The mac-mask specifies the portion of the MAC address to match against and is in MAC address format.

Step 3

show mac-list name

Example:

switch(config)# show mac-list AllowMac

(Optional) Displays information about MAC lists.

Step 4

copy running-config startup-config

Example:

switch# copy running-config startup-config

(Optional) Saves this configuration change.

Configuring AS-path Lists

You can specify an AS-path list filter on both inbound and outbound BGP routes. Each filter is an access list based on regular expressions. If the regular expression matches the representation of the AS-path attribute of the route as an ASCII string, the permit or deny condition applies.

SUMMARY STEPS

1. configure terminal

2. ip as-path access-list name {deny | permit} expression

3. (Optional) show {ip | ipv6} as-path list name

4. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

ip as-path access-list name {deny | permit} expression

Example:

switch(config)# ip as-path access-list Allow40 permit 40

Creates a BGP AS-path list using a regular expression.

Step 3

show {ip | ipv6} as-path-access-list name

Example:

switch(config)# show ip as-path-access-list Allow40

(Optional) Displays information about as-path access lists.

Step 4

copy running-config startup-config

Example:

switch# copy running-config startup-config

(Optional) Saves this configuration change.

The following example shows how to create an AS-path list with two entries and apply the AS path list to a BGP neighbor:

switch# configure terminal

switch(config)# ip as-path access-list AllowAS permit 64510

switch(config)# ip as-path access-list AllowAS permit 64496

switch(config)# copy running-config startup-config

switch(config)# router bgp 65536:20

switch(config-router)# neighbor 192.0.2.1/16 remote-as 65535:20

switch(config-router-neighbor)# address-family ipv4 unicast

switch(config-router-neighbor-af)# filter-list AllowAS in

Configuring Community Lists

You can use community lists to filter BGP routes based on the community attribute. The community number consists of a 4-byte value in the aa:nn format. The first two bytes represent the autonomous system number, and the last two bytes represent a user-defined network number.

When you configure multiple values in the same community list statement, all community values must match to satisfy the community list filter. When you configure multiple values in separate community list statements, the first list that matches a condition is processed.

Use community lists in a match statement to filter BGP routes based on the community attribute.

SUMMARY STEPS

1. configure terminal

2. ip community-list standard list-name {deny | permit} [community-list] [internet] [local-AS] [no-advertise] [no-export]

or

ip community-list expanded list-name {deny | permit} expression

3. (Optional) show ip community-list name

4. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

ip community-list standard list-name {deny | permit} [community-list] [internet] [local-AS] [no-advertise] [no-export]

Example:

switch(config)# ip community-list standard BGPCommunity permit no-advertise 65536:20

Creates a standard BGP community list. The list-name can be any case-sensitive, alphanumeric string up to 63 characters. The community-list can be one or more communities in the aa:nn format.

ip community-list expanded list-name {deny | permit} expression

Example:

switch(config)# ip community-list expanded BGPComplex deny 50000:[0-9][0-9]_

Creates an expanded BGP community list using a regular expression.

Step 3

show ip community-list name

Example:

switch(config)# show ip community-list BGPCommunity

(Optional) Displays information about community lists.

Step 4

copy running-config startup-config

Example:

switch# copy running-config startup-config

(Optional) Saves this configuration change.

The following example shows how to create a community list with two entries:

switch# configure terminal

switch(config)# ip community-list standard BGPCommunity permit no-advertise 65536:20

switch(config)# ip community-list standard BGPCommunity permit local-AS no-export

switch(config)# copy running-config startup-config

Configuring Extended Community Lists

You can use extended community lists to filter BGP routes based on the community attribute. The community number consists of a 6-byte value in the aa4:nn format. The first four bytes represent the autonomous system number, and the last two bytes represent a user-defined network number.

When you configure multiple values in the same extended community list statement, all extended community values must match to satisfy the extended community list filter. When you configure multiple values in separate extended community list statements, the first list that matches a condition is processed.

Use extended community lists in a match statement to filter BGP routes based on the extended community attribute.

SUMMARY STEPS

1. configure terminal

2. ip extcommunity-list standard list-name {deny | permit} 4bytegeneric {transitive | non-transitive} aa4:nn

or

ip extcommunity-list expanded list-name {deny | permit} expression

3. (Optional) show ip extcommunity-list name

4. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

ip extcommunity-list standard list-name {deny | permit} 4bytegeneric {transitive | nontransitive} community1 [community2...]

Example:

switch(config)# ip extcommunity-list standard BGPExtCommunity permit 4bytegeneric transitive 65536:20

Creates a standard BGP extended community list. The community can be one or more extended communities in the aa4:nn format.

ip extcommunity-list expanded list-name {deny | permit} expression

Example:

switch(config)# ip extcommunity-list expanded BGPExtComplex deny 1.5:[0-9][0-9]_

Creates an expanded BGP extended community list using a regular expression.

Step 3

show ip community-list name

Example:

switch(config)# show ip community-list BGPCommunity

(Optional) Displays information about extended community lists.

Step 4

copy running-config startup-config

Example:

switch# copy running-config startup-config

(Optional) Saves this configuration change.

The following example shows how to create a generic specific extended community list:

switch# configure terminal

switch(config)# ip extcommunity-list standard test1 permit 4bytegeneric transitive 65536:40 65536:60

switch(config)# copy running-config startup-config

Configuring Route Maps

You can use route maps for route redistribution or route filtering. Route maps can contain multiple match criteria and multiple set criteria.

Configuring a route map for BGP triggers an automatic soft clear or refresh of BGP neighbor sessions.

SUMMARY STEPS

1. configure terminal

2. route-map map-name [permit | deny] [seq]

3. (Optional) continue seq

4. (Optional) exit

5. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

route-map map-name [permit | deny] [seq]

Example:

switch(config)# route-map Testmap permit 10

switch(config-route-map)#

Creates a route map or enters route-map configuration mode for an existing route map. Use seq to order the entries in a route map.

Step 3

continue seq

Example:

switch(config-route-map)# continue 10

(Optional) Determines what sequence statement to process next in the route map. Used only for filtering and redistribution.

Step 4

exit

Example:

switch(config-route-map)# exit

(Optional) Exits route-map configuration mode.

Step 5

copy running-config startup-config

Example:

switch(config)# copy running-config startup-config

(Optional) Saves this configuration change.

You can configure the following optional match parameters for route maps in route-map configuration mode:

Note The default-information originate command ignores match statements in the optional route map.

Command

Purpose

match as-path name [name...]

Example:

switch(config-route-map)# match as-path Allow40

Matches against one or more AS-path lists. Create the AS-path list with the ip as-path access-list command.

match as-number {number [,number...] | as-path-list name [name...]}

Example:

switch(config-route-map)# match as-number 33,50-60

Matches against one or more AS numbers or AS-path lists. Create the AS-path list with the ip as-path access-list command. The number range is from 1 to 65535. The AS-path list name can be any case-sensitive, alphanumeric string up to 63 characters.

match community name [name...][exact-match]

Example:

switch(config-route-map)# match community BGPCommunity

Matches against one or more community lists. Create the community list with the ip community-list command.

match extcommunity name [name...][exact-match]

Example:

switch(config-route-map)# match extcommunity BGPextCommunity

Matches against one or more extended community lists. Create the community list with the ip extcommunity-list command.

match interface interface-type number [interface-type number...]

Example:

switch(config-route-map)# match interface e 1/2

Matches any routes that have their next hop out one of the configured interfaces. Use ? to find a list of supported interface types.

match ip address prefix-list name [name...]

Example:

switch(config-route-map)# match ip address prefix-list AllowPrefix

Matches against one or more IPv4 prefix lists. Use the ip prefix-list command to create the prefix list.

match ipv6 address prefix-list name [name...]

Example:

switch(config-route-map)# match ip address prefix-list AllowIPv6Prefix

Matches against one or more IPv6 prefix lists. Use the ipv6 prefix-list command to create the prefix list.

match ip multicast [source ipsource] [[group ipgroup] [rp iprp]]

Example:

switch(config-route-map)# match ip multicast rp 192.0.2.1

Matches an IPv4 multicast packet based on the multicast source, group, or rendezvous point.

match ipv6 multicast [source ipsource] [[group ipgroup] [rp iprp]]

Example:

switch(config-route-map)# match ip multicast source 2001:0DB8::1

Matches an IPv6 multicast packet based on the multicast source, group, or rendezvous point.

match ip next-hop prefix-list name [name...]

Example:

switch(config-route-map)# match ip next-hop prefix-list AllowPrefix

Matches the IPv4 next-hop address of a route to one or more IP prefix lists. Use the ip prefix-list command to create the prefix list.

match ipv6 next-hop prefix-list name [name...]

Example:

switch(config-route-map)# match ipv6 next-hop prefix-list AllowIPv6Prefix

match ip route-source prefix-list name [name...]

Example:

switch(config-route-map)# match ip route-source prefix-list AllowPrefix

Matches the IPv4 route source address of a route to one or more IP prefix lists. Use the ip prefix-list command to create the prefix list.

match ipv6 route-source prefix-list name [name...]

Example:

switch(config-route-map)# match ipv6 route-source prefix-list AllowIPv6Prefix

Matches the IPv6 route-source address of a route to one or more IP prefix lists. Use the ipv6 prefix-list command to create the prefix list.

match mac-list name [name...]

Example:

switch(config-route-map)# match mac-list AllowMAC

Matches against one or more MAC lists. Use the mac-list command to create the MAC list.

match metric value [+- deviation.] [value..]

Example:

switch(config-route-map)# match metric 50 + 10

Matches the route metric against one or more metric values or value ranges. Use +- deviation argument to set a metric range. The route map matches any route metric that falls within the range:

value - deviation to value + deviation.

match route-type route-type

Example:

switch(config-route-map)# match route-type level 1 level 2

Matches against a type of route. The route-type can be one or more of the following:

- external

- internal

- level-1

- level-2

- local

- nssa-external

- type-1

- type-2

match tag tagid [tagid...]

Example:

switch(config-route-map)# match tag 2

Matches a route against one or more tags for filtering or redistribution.

match vlan vlan-id [vlan-range]

Example:

switch(config-route-map)# match vlan 3, 5-10

Matches against a VLAN.

You can configure the following optional set parameters for route maps in route-map configuration mode:

Command

Purpose

set as-path {tag | prepend {last-as number | as-1 [as-2...]}}

Example:

switch(config-route-map)# set as-path prepend 10 100 110

Modifies an AS-path attribute for a BGP route. You can prepend the configured number of last AS numbers or a string of particular AS-path values (as-1 as-2...as-n).

set comm-list name delete

Example:

switch(config-route-map)# set comm-list BGPCommunity delete

Removes communities from the community attribute of an inbound or outbound BGP route update. Use the ip community-list command to create the community list.

set community {none | additive | local-AS | no-advertise | no-export | community-1 [community-2...]}

Example:

switch(config-route-map)# set community local-AS

Sets the community attribute for a BGP route update.
commands in the same sequence of a route map attribute, the deletion operation is performed before the set operation. command in BGP neighbor address family configuration mode to propagate BGP community attributes to BGP peers.

set dampening halflife reuse suppress duration

Example:

switch(config-route-map)# set dampening 30 1500 10000 120

Sets the following BGP route dampening parameters:

- halflife —The range is from 1 to 45 minutes. The default is 15.

- reuse —The range is from is 1 to 20000 seconds. The default is 750.

- suppress —The range is from is 1 to 20000. The default is 2000.

- duration —The range is from is 1 to 255 minutes. The default is 60.

set extcomm-list name delete

Example:

switch(config-route-map)# set extcomm-list BGPextCommunity delete

Removes communities from the extended community attribute of an inbound or outbound BGP route update. Use the ip extcommunity-list command to create the extended community list.

set extcommunity 4byteas-generic {transitive | nontransitive} {none | additive] community-1 [community-2...]}

Example:

switch(config-route-map)# set extcommunity generic transitive 1.0:30

Sets the extended community attribute for a BGP route update.
commands in the same sequence of a route map attribute, the deletion operation is performed before the set operation. command in BGP neighbor address family configuration mode to propagate BGP extended community attributes to BGP peers.

set extcommunity cost community-id1 cost [igp | pre-bestpath] [community-id2...]}

Example:

switch(config-route-map)# set extcommunity cost 33 1.0:30

Sets the cost community attribute for a BGP route update. This attribute allows you to customize the BGP best path selection process for a local autonomous system or confederation. The community-id range is from 0 to 255. The cost range is from 0 to 4294967295. The path with the lowest cost is preferred. For paths with equal cost, the path with the lowest community ID is preferred.

The igp keyword compares the cost after the IGP cost comparison. The pre-bestpath keyword compares before all other steps in the bestpath algorithm.

set extcommunity rt community-1 [additive] [community-2...]}

Example:

switch(config-route-map)# set extcommunity rt 1.0:30

Sets the extended community route target attribute for a BGP route update. The community value can be a 2-byte AS number:4-byte network number, a 4-byte AS number:2-byte network number, or an IP address:2-byte network number.

Use the additive keyword to add a route target to an existing extended community route target attribute.

set forwarding-address

Example:

switch(config-route-map)# set forwarding-address

Sets the forwarding address for OSPF.

set level {backbone | level-1 | level-1-2 | level-2}

Example:

switch(config-route-map)# set level backbone

Sets what area to import routes to for IS-IS. The options for IS-IS are level-1, level-1-2, or level-2. The default is level-1.

set local-preference value

Example:

switch(config-route-map)# set local-preference 4000

Sets the BGP local preference value. The range is from 0 to 4294967295.

set metric [+ | -]bandwidth-metric

Example:

switch(config-route-map)# set metric +100

Adds or subtracts from the existing metric value. The metric is in Kb/s. The range is from 0 to 4294967295.

set metric bandwidth [delay reliability load mtu]

Example:

switch(config-route-map)# set metric 33 44 100 200 1500

Sets the route metric values.

Metrics are as follows:

- metric0 —Bandwidth in Kb/s. The range is from 0 to 4294967295.

- metric1 —Delay in 10-microsecond units.

- metric2 —Reliability. The range is from 0 to 255 (100 percent reliable).

- metric3 —Loading. The range is from 1 to 200 (100 percent loaded).

- metric4 —MTU of the path. The range is from 1 to 4294967295.

set metric-type {external | internal | type-1 | type-2}

Example:

switch(config-route-map)# set metric-type internal

Sets the metric type for the destination routing protocol. The options are as follows:

external—IS-IS external metric

internal— IGP metric as the MED for BGP

type-1—OSPF external type 1 metric

type-2—OSPF external type 2 metric

set nssa-only

Example:

switch(config-route-map)# set nssa-only

Sets Type-7 LSA generated on ASBR with no P bit set. This prevents Type-7 to Type-5 LSA translation in OSPF.

set origin {egp as-number | igp | incomplete}

Example:

switch(config-route-map)# set origin incomplete

Sets the BGP origin attribute. The EGP as-number range is from 0 to 65535.

set tag name

Example:

switch(config-route-map)# set tag 33

Sets the tag value for the destination routing protocol. The name parameter is an unsigned integer.

set weight count

Example:

switch(config-route-map)# set weight 33

Sets the weight for the BGP route. The range is from 0 to 65535.

The set metric-type internal command affects an outgoing policy and an eBGP neighbor only. If you configure both the metric and metric-type internal commands in the same BGP peer outgoing policy, Cisco NX-OS ignores the metric-type internal command.

Verifying the Route Policy Manager Configuration

Command

Purpose

show ip community-list [name]

Displays information about a community list.

show ip extcommunity-list [name]

Displays information about an extended community list.

show [ip | ipv6] prefix-list [name]

Displays information about an IPv4 or IPv6 prefix list.

show route-map [name]

Displays information about a route map.

Configuration Examples for Route Policy Manager

This example shows how to use an address family to configure Route Policy Manager so that any unicast and multicast routes from neighbor 209.0.2.1 are accepted if they match prefix-list AllowPrefix:

router bgp 64496

neighbor 209.0.2.1 remote-as 64497

address-family ipv4 unicast

route-map filterBGP in

route-map filterBGP

match ip address prefix-list AllowPrefix

ip prefix-list AllowPrefix 10 permit 192.0.2.0/24

ip prefix-list AllowPrefix 20 permit 209.165.201.0/27

Related Topics

The following topics can give more information on Route Policy Manager:

- Chapter 10, “Configuring Basic BGP”

- Chapter 17, “Configuring Policy-Based Routing”

Additional References

For additional information related to implementing IP, see the following sections:

- Related Documents

- Standards

Related Documents

Related Topic

Document Title

Route Policy Manager CLI commands

Cisco Nexus 7000 Series NX-OS Unicast Routing Command Reference, Release 5.x

VDCs and VRFs

Cisco Nexus 7000 Series NX-OS Virtual Device Context Configuration Guide, Release 5.x

Standards

Standards

Title

No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.

—

Feature History for Route Policy Manager

Table 16-2 Feature History for Route Policy Manager

Feature Name

Releases

Feature Information

MPLS set clauses

5.2(1)

Added support for set extcommunity cost, set extcommunity rt,and set nssa-only commands.

MAC lists , metric, and VLANs

5.0(2)

Added support for match mac-list, match metric, and match vlan commands.

Extended community lists

4.2(1)

Added support for generic specific extended community lists.

Match interfaces

4.1(2)

Added support to match a list of interfaces in a route map.

Match AS numbers

4.1(2)

Added support to match a range of AS numbers in a route map.

Route Policy Manager

4.0(1)

Configuring Layer 3 Virtualization

This chapter describes how to configure Layer 3 virtualization on the Cisco NX-OS device.

This chapter includes the following sections:

- Layer 3 Virtualization

- Licensing Requirements for VRFs

- Prerequisites for VRF

- Guidelines and Limitations for VRFs

- Default Settings

- Configuring VRFs

- Verifying the VRF Configuration

- Configuration Examples for VRF

- Additional References

- Feature History for VRF

Layer 3 Virtualization

This section contains the following topics:

- Overview of Layer 3 Virtualization

- VRF and Routing

- VRF-Aware Services

Overview of Layer 3 Virtualization

Cisco NX-OS supports a hierarchy of virtualization that can divide the physical system resources into multiple virtual device contexts (VDCs). Each VDC acts as a standalone device with both Layer 2 and Layer 3 services available. You can configure up to 4 VDCs, including the default VDC. See the Cisco Nexus 7000 Series NX-OS Virtual Device Context Configuration Guide, Release 5.x, for more information on VDCs.

Cisco NX-OS further virtualizes each VDC to support virtual routing and forwarding instances (VRFs). You can configure multiple VRFs in a VDC. Each VRF contains a separate address space with unicast and multicast route tables for IPv4 and IPv6 and makes routing decisions independent of any other VRF.

Figure 14-1 shows multiple independent VRFs in two different VDCs.

Figure 14-1 Multiple VRFs in VDCs

A VRF name is local to a VDC, so you can configure two VRFs with the same name if the VRFs exist in different VDCs. In Figure 14-1, VRF A in VDC 2 is independent of VRF B and VRF A in VDC n.

Each router has a management VRF and a default VRF:

Management VRF

- The management VRF is for management purposes only.

- Only the mgmt 0 interface can be in the management VRF.

- The mgmt 0 interface cannot be assigned to another VRF.

- The mgmt 0 interface is shared among multiple VDCs.

- No routing protocols can run in the management VRF (static only).

Default VRF

- All Layer 3 interfaces exist in the default VRF until they are assigned to another VRF.

- Routing protocols run in the default VRF context unless another VRF context is specified.

- The default VRF uses the default routing context for all show commands.

- The default VRF is similar to the global routing table concept in Cisco IOS.

VRF and Routing

All unicast and multicast routing protocols support VRFs. When you configure a routing protocol in a VRF, you set routing parameters for the VRF that are independent of routing parameters in another VRF for the same routing protocol instance.

You can assign interfaces and route protocols to a VRF to create virtual Layer 3 networks. An interface exists in only one VRF. Figure 14-2 shows one physical network split into two virtual networks with two VRFs. Routers Z, A, and B exist in VRF Red and form one address domain. These routers share route updates that do not include Router C because Router C is configured in a different VRF.

Figure 14-2 VRFs in a Network

By default, Cisco NX-OS uses the VRF of the incoming interface to select which routing table to use for a route lookup. You can configure a route policy to modify this behavior and set the VRF that Cisco NX-OS uses for incoming packets. See Chapter 17, “Configuring Policy-Based Routing” for more information.

Cisco NX-OS supports route leaking (import or export) between VRFs, both in VRF lite and MPLS VPN scenarios. For more information on route leaking, see the Cisco Nexus 7000 Series NX-OS MPLS Configuration Guide.

VRF-Aware Services

A fundamental feature of the Cisco NX-OS architecture is that every IP-based feature is VRF aware.

The following VRF-aware services can select a particular VRF to reach a remote server or to filter information based on the selected VRF:

- AAA—See the Cisco Nexus 7000 Series NX-OS Security Configuration Guide, Release 5.x for more information.

- Call Home—See the Cisco Nexus 7000 Series NX-OS System Management Configuration Guide, Release 5.x for more information.

- DNS—See Chapter 4, “Configuring DNS” for more information.

- GLBP—See Chapter 18, “Configuring GLBP” for more information.

- HSRP—See Chapter 19, “Configuring HSRP” for more information.

- HTTP—See the Cisco Nexus 7000 Series NX-OS Fundamentals Configuration Guide, Release 5.x , for more information.

- NetFlow—See the Cisco Nexus 7000 Series NX-OS System Management Configuration Guide, Release 5.x , for more information.

- NTP—See the Cisco Nexus 7000 Series NX-OS System Management Configuration Guide, Release 5.x , for more information.

- RADIUS—See the Cisco Nexus 7000 Series NX-OS Security Configuration Guide, Release 5.x , for more information.

- Ping and Traceroute —See the Cisco Nexus 7000 Series NX-OS Fundamentals Configuration Guide, Release 5.x , for more information.

- SSH—See the Cisco Nexus 7000 Series NX-OS Fundamentals Configuration Guide, Release 5.x , for more information.

- SNMP—See the Cisco Nexus 7000 Series NX-OS System Management Configuration Guide, Release 5.x , for more information.

- Syslog—See the Cisco Nexus 7000 Series NX-OS System Management Configuration Guide, Release 5.x , for more information.

- TACACS+—See the Cisco Nexus 7000 Series NX-OS Security Configuration Guide, Release 5.x , for more information.

- TFTP—See the Cisco Nexus 7000 Series NX-OS Fundamentals Configuration Guide, Release 5.x , for more information.

- VRRP—See Chapter 20, “Configuring VRRP” for more information.

- XML—See the Cisco NX-OS XML Management Interface User Guide, Release 5.x , for more information.

See the appropriate configuration guide for each service for more information on configuring VRF support in that service.

This section contains the following topics:

- Reachability

- Filtering

- Combining Reachability and Filtering

Reachability

Reachability indicates which VRF contains the routing information needed to get to the server providing the service. For example, you can configure an SNMP server that is reachable on the management VRF. When you configure that server address on the router, you also configure which VRF that Cisco NX-OS must use to reach the server.

Figure 14-3 shows an SNMP server that is reachable over the management VRF. You configure Router A to use the management VRF for the SNMP server host 192.0.2.1.

Figure 14-3 Service VRF Reachability

Filtering

Filtering allows you to limit the type of information that goes to a VRF-aware service based on the VRF. For example, you can configure a syslog server to support a particular VRF. Figure 14-4 shows two syslog servers with each server supporting one VRF. syslog server A is configured in VRF Red, so Cisco NX-OS sends only system messages generated in VRF Red to syslog server A.

Figure 14-4 Service VRF Filtering

Combining Reachability and Filtering

You can combine reachability and filtering for VRF-aware services. You can configure the VRF that Cisco NX-OS uses to connect to that service as well as the VRF that the service supports. If you configure a service in the default VRF, you can optionally configure the service to support all VRFs.

Figure 14-5 shows an SNMP server that is reachable on the management VRF. You can configure the SNMP server to support only the SNMP notifications from VRF Red, for example.

Figure 14-5 Service VRF Reachability Filtering

Licensing Requirements for VRFs

The following table shows the licensing requirements for this feature:

Product

License Requirement

Cisco NX-OS

VRFs require no license. Any feature not included in a license package is bundled with the Cisco NX-OS system images and is provided at no extra charge to you. For a complete explanation of the Cisco NX-OS licensing scheme, see the Cisco NX-OS Licensing Guide.

Prerequisites for VRF

VRFs have the following prerequisites:

- You must install the Advanced Services license to use VDCs besides the default VDC.

Guidelines and Limitations for VRFs

VRFs have the following configuration guidelines and limitations:

- When you make an interface a member of an existing VRF, Cisco NX-OS removes all Layer 3 configurations. You should configure all Layer 3 parameters after adding an interface to a VRF.

- You should add the mgmt0 interface to the management VRF and configure the mgmt0 IP address and other parameters after you add it to the management VRF.

- If you configure an interface for a VRF before the VRF exists, the interface is operationally down until you create the VRF.

- Cisco NX-OS creates the default and management VRFs by default. You should make the mgmt0 interface a member of the management VRF.

- The write erase boot command does not remove the management VRF configurations. You must use the write erase command and then the write erase boot command.

Default Settings

Table 14-1 lists the default settings for VRF parameters.

Table 14-1 Default VRF Parameters

Parameters

Default

Configured VRFs

Default, management

routing context

Default VRF

Configuring VRFs

This section contains the following topics:

- Creating a VRF

- Assigning VRF Membership to an Interface

- Configuring VRF Parameters for a Routing Protocol

- Configuring a VRF-Aware Service

- Setting the VRF Scope

Note If you are familiar with the Cisco IOS CLI, be aware that the Cisco NX-OS commands for this feature might differ from the Cisco IOS commands that you would use.

Creating a VRF

You can create a VRF in a VDC.

BEFORE YOU BEGIN

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. vrf context vrf-name

3. (Optional) ip route {ip-prefix | ip-addr ip-mask} {[next-hop | nh-prefix] | [interface next-hop | nh-prefix]} [tag tag-value [pref]

4. (Optional) show vrf [vrf-name]

5. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

vrf context name

Example:

switch(config)# vrf context Enterprise

switch(config-vrf)#

Creates a new VRF and enters VRF configuration mode. The name can be any case-sensitive, alphanumeric string up to 32 characters.

Step 3

ip route {ip-prefix | ip-addr ip-mask} {[next-hop | nh-prefix] | [interface next-hop | nh-prefix]} [tag tag-value [pref]

Example:

switch(config-vrf)# ip route 192.0.2.0/8 ethernet 1/2 192.0.2.4

(Optional) Configures a static route and the interface for this static route. You can optionally configure the next-hop address. The preference value sets the administrative distance. The range is from 1 to 255. The default is 1.

Step 4

show vrf [vrf-name]

Example:

switch(config-vrf)# show vrf Enterprise

(Optional) Displays VRF information.

Step 5

copy running-config startup-config

Example:

switch(config)# copy running-config startup-config

(Optional) Saves this configuration change.

To delete the VRF and the associated configuration, use the following command in global configuration mode:

Command

Purpose

no vrf context name

Example:

switch(config)# no vrf context Enterprise

Deletes the VRF and all associated configurations.

Any commands available in global configuration mode are also available in VRF configuration mode.

This example shows how to create a VRF and add a static route to the VRF:

switch# configure terminal

switch(config)# vrf context Enterprise

switch(config-vrf)# ip route 192.0.2.0/8 ethernet 1/2

switch(config-vrf)# exit

switch(config)# copy running-config startup-config

Assigning VRF Membership to an Interface

You can make an interface a member of a VRF.

BEFORE YOU BEGIN

Ensure that you are in the correct VDC (or use the switchto vdc command).

Assign the IP address for an interface after you have configured the interface for a VRF.

SUMMARY STEPS

1. configure terminal

2. interface interface-type slot/port

3. vrf member vrf-name

4. ip-address ip-prefix/length

5. (Optional) show vrf vrf-name interface interface-type number

6. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

interface interface-type slot/port

Example:

switch(config)# interface ethernet 1/2

switch(config-if)#

Enters interface configuration mode.

Step 3

vrf member vrf-name

Example:

switch(config-if)# vrf member RemoteOfficeVRF

Adds this interface to a VRF.

Step 4

ip address ip-prefix/length

Example:

switch(config-if)# ip address 192.0.2.1/16

Configures an IP address for this interface. You must do this step after you assign this interface to a VRF.

Step 5

show vrf vrf-name interface interface-type number

Example:

switch(config-vrf)# show vrf Enterprise interface ethernet 1/2

(Optional) Displays VRF information.

Step 6

copy running-config startup-config

Example:

switch(config)# copy running-config startup-config

(Optional) Saves this configuration change.

The following example shows how to add an interface to the VRF:

switch# configure terminal

switch(config)# interface ethernet 1/2

switch(config-if)# vrf member RemoteOfficeVRF

switch(config-if)# ip address 192.0.2.1/16

switch(config-if)# copy running-config startup-config

Configuring VRF Parameters for a Routing Protocol

You can associate a routing protocol with one or more VRFs. See the appropriate chapter for information on how to configure VRFs for the routing protocol. This section uses OSPFv2 as an example protocol for the detailed configuration steps.

BEFORE YOU BEGIN

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. router ospf instance-tag

3. vrf vrf-name

4. (Optional) maximum-paths paths

5. interface interface-type slot/port

6. vrf member vrf-name

7. ip address ip-prefix/length

8. ip router ospf instance-tag area area-id

9. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

router ospf instance-tag

Example:

switch(config-vrf)# router ospf 201

switch(config-router)#

Creates a new OSPFv2 instance with the configured instance tag.

Step 3

vrf vrf-name

Example:

switch(config-router)# vrf RemoteOfficeVRF

switch(config-router-vrf)#

Enters VRF configuration mode.

Step 4

maximum-paths paths

Example:

switch(config-router-vrf)# maximum-paths 4

(Optional) Configures the maximum number of equal OSPFv2 paths to a destination in the route table for this VRF. Used for load balancing.

Step 5

interface interface-type slot/port

Example:

switch(config)# interface ethernet 1/2

switch(config-if)#

Enters interface configuration mode.

Step 6

vrf member vrf-name

Example:

switch(config-if)# vrf member RemoteOfficeVRF

Adds this interface to a VRF.

Step 7

ip address ip-prefix/length

Example:

switch(config-if)# ip address 192.0.2.1/16

Configures an IP address for this interface. You must do this step after you assign this interface to a VRF.

Step 8

ip router ospf instance-tag area area-id

Example:

switch(config-if)# ip router ospf 201 area 0

Assigns this interface to the OSPFv2 instance and area configured.

Step 9

copy running-config startup-config

Example:

switch(config)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to create a VRF and add an interface to the VRF:

switch# configure terminal

switch(config)# vrf context RemoteOfficeVRF

switch(config-vrf)# exit

switch(config)# router ospf 201

switch(config-router)# vrf RemoteOfficeVRF

switch(config-router-vrf)# maximum-paths 4

switch(config-router-vrf)# interface ethernet 1/2

switch(config-if)# vrf member RemoteOfficeVRF

switch(config-if)# ip address 192.0.2.1/16

switch(config-if)# ip router ospf 201 area 0

switch(config-if)# exit

switch(config)# copy running-config startup-config

Configuring a VRF-Aware Service

You can configure a VRF-aware service for reachability and filtering. See the “VRF-Aware Services” section for links to the appropriate chapter or configuration guide for information on how to configure the service for VRFs. This section uses SNMP and IP domain lists as example services for the detailed configuration steps.

BEFORE YOU BEGIN

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. snmp-server host ip-address [filter-vrf vrf-name] [use-vrf vrf-name]

3. vrf context [vrf-name]

4. ip domain-list domain-name [all-vrfs][use-vrf vrf-name]

5. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

snmp-server host ip-address [filter-vrf vrf-name] [use-vrf vrf-name]

Example:

switch(config)# snmp-server host 192.0.2.1 use-vrf Red

switch(config-vrf)#

Configures a global SNMP server and configures the VRF that Cisco NX-OS uses to reach the service. Use the filter-vrf keyword to filter information from the selected VRF to this server.

Step 3

vrf context vrf-name

Example:

switch(config)# vrf context Blue

switch(config-vrf)#

Creates a new VRF.

Step 4

ip domain-list domain-name [all-vrfs][use-vrf vrf-name]

Example:

switch(config-vrf)# ip domain-list List all-vrfs use-vrf Blue

switch(config-vrf)#

Configures the domain list in the VRF and optionally configures the VRF that Cisco NX-OS uses to reach the domain name listed.

Step 5

copy running-config startup-config

Example:

switch(config)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to send SNMP information for all VRFs to SNMP host 192.0.2.1, reachable on VRF Red:

switch# configure terminal

switch(config)# snmp-server host 192.0.2.1 for-all-vrfs use-vrf Red

switch(config)# copy running-config startup-config

This example shows how to filter SNMP information for VRF Blue to SNMP host 192.0.2.12, reachable on VRF Red:

switch# configure terminal

switch(config)# vrf context Blue

switch(config-vrf)# snmp-server host 192.0.2.12 use-vrf Red

switch(config)# copy running-config startup-config

Setting the VRF Scope

You can set the VRF scope for all EXEC commands (for example, show commands). This automatically restricts the scope of the output of EXEC commands to the configured VRF. You can override this scope by using the VRF keywords available for some EXEC commands.

To set the VRF scope, use the following command in EXEC mode:

Command

Purpose

routing-context vrf vrf-name

Example:

switch# routing-context vrf red

switch%red#

Sets the routing context for all EXEC commands. Default routing context is the default VRF.

To return to the default VRF scope, use the following command in EXEC mode:

Command

Purpose

routing-context vrf default

Example:

switch%red# routing-context vrf default

switch#

Sets the default routing context.

Verifying the VRF Configuration

To display VRF configuration information, perform one of the following tasks:

Command

Purpose

show vrf [vrf-name]

Displays the information for all or one VRF.

show vrf [vrf-name] detail

Displays detailed information for all or one VRF.

show vrf [vrf-name] [interface interface-type slot/port]

Displays the VRF status for an interface.

Configuration Examples for VRF

This example shows how to configure VRF Red, add an SNMP server to that VRF, and add an instance of OSPF to VRF Red:

configure terminal

vrf context Red

snmp-server host 192.0.2.12 use-vrf Red

router ospf 201

vrf Red

interface ethernet 1/2

vrf member Red

ip address 192.0.2.1/16

ip router ospf 201 area 0

This example shows how to configure VRF Red and Blue, add an instance of OSPF to each VRF, and create an SNMP context for each OSPF instance in each VRF:

configure terminal

!Create the VRFs

vrf context Red

vrf context Blue

vrf context Green

!Create the OSPF instances and associate them with a single VRF or multiple VRFs (recommended)

feature ospf

router ospf Lab

vrf Red

!

router ospf Production

vrf Blue

router-id 1.1.1.1

vrf Green

router-id 2.2.2.2

!Configure one interface to use ospf Lab on VRF Red

interface ethernet 1/2

vrf member Red

ip address 192.0.2.1/16

ip router ospf Lab area 0

no shutdown

!Configure another interface to use ospf Production on VRF Blue

interface ethernet 10/2

vrf member Blue

ip address 192.0.2.1/16

ip router ospf Production area 0

no shutdown

!

interface ethernet 10/3

vrf member Green

ip address 192.0.2.1/16

ip router ospf Production area 0

no shutdown

!configure the SNMP server

snmp-server user admin network-admin auth md5 nbv-12345

snmp-server community public ro

!Create the SNMP contexts for each VRF

snmp-server context lab instance Lab vrf Red

snmp-server context production instance Production vrf Blue

!Use the SNMP context lab to access the OSPF-MIB values for the OSPF instance Lab in VRF Red in this example.

Use the SNMP context lab to access the OSPF-MIB values for the OSPF instance Lab in VRF Red in this example.

Additional References

For additional information related to implementing virtualization, see the following sections:

- Related Documents

- Standards

Related Documents

Related Topic

Document Title

VRF CLI

Cisco Nexus 7000 Series NX-OS Unicast Routing Command Reference, Release 5.x

VRFs

Cisco Nexus 7000 Series NX-OS Fundamentals Configuration Guide, Release 5.x

Cisco Nexus 7000 Series NX-OS MPLS Configuration Guide

Cisco Nexus 7000 Series NX-OS System Management Configuration Guide, Release 5.x

VDCs

Cisco Nexus 7000 Series NX-OS Virtual Device Context Configuration Guide, Release 5.x

Standards

Standards

Title

No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.

—

Feature History for VRF

Table 14-2 lists the release history for this feature.

Table 14-2 Feature History for VRF

Feature Name

Releases

Feature Information

VRF

4.0(1)

This feature was introduced.

Configuring VRRP

This chapter describes how to configure the Virtual Router Redundancy Protocol (VRRP) on the Cisco NX-OS device.

This chapter includes the following sections:

- Information About VRRP

- Licensing Requirements for VRRP

- Guidelines and Limitations for VRRP

- Default Settings

- Configuring VRRP

- Verifying the VRRP Configuration

- Monitoring VRRP Statistics

- Configuration Examples for VRRP

- Additional References

- Feature History for VRRP

Information About VRRP

VRRP allows for transparent failover at the first-hop IP router by configuring a group of routers to share a virtual IP address. VRRP selects a master router in that group to handle all packets for the virtual IP address. The remaining routers are in standby and take over if the master router fails.

This section includes the following topics:

- VRRP Operation

- VRRP Benefits

- Multiple VRRP Groups

- VRRP Router Priority and Preemption

- vPC and VRRP

- VRRP Advertisements

- VRRP Authentication

- VRRP Tracking

- BFD

- High Availability

- Virtualization Support

VRRP Operation

A LAN client can determine which router should be the first hop to a particular remote destination by using a dynamic process or static configuration. Examples of dynamic router discovery are as follows:

- Proxy ARP—The client uses Address Resolution Protocol (ARP) to get the destination it wants to reach, and a router responds to the ARP request with its own MAC address.

- Routing protocol—The client listens to dynamic routing protocol updates (for example, from Routing Information Protocol [RIP]) and forms its own routing table.

- ICMP Router Discovery Protocol (IRDP) client—The client runs an Internet Control Message Protocol (ICMP) router discovery client.

The disadvantage to dynamic discovery protocols is that they incur some configuration and processing overhead on the LAN client. Also, if a router fails, the process of switching to another router can be slow.

An alternative to dynamic discovery protocols is to statically configure a default router on the client. Although, this approach simplifies client configuration and processing, it creates a single point of failure. If the default gateway fails, the LAN client is limited to communicating only on the local IP network segment and is cut off from the rest of the network.

VRRP can solve the static configuration problem by enabling a group of routers (a VRRP group) to share a single virtual IP address. You can then configure the LAN clients with the virtual IP address as their default gateway.

Figure 20-1 shows a basic VLAN topology. In this example, Routers A, B, and C form a VRRP group. The IP address of the group is the same address that was configured for the Ethernet interface of Router A (10.0.0.1).

Figure 20-1 Basic VRRP Topology

Because the virtual IP address uses the IP address of the physical Ethernet interface of Router A, Router A is the master (also known as the IP address owner). As the master, Router A owns the virtual IP address of the VRRP group and forwards packets sent to this IP address. Clients 1 through 3 are configured with the default gateway IP address of 10.0.0.1.

Routers B and C function as backups. If the master fails, the backup router with the highest priority becomes the master and takes over the virtual IP address to provide uninterrupted service for the LAN hosts. When router A recovers, it becomes the master again. For more information, see the “VRRP Router Priority and Preemption” section.

Note In Cisco NX-OS Release 4.1(2) and later, packets received on a routed port destined for the VRRP virtual IP address terminates on the local router, regardless of whether that router is the master VRRP router or a backup VRRP router. This includes ping and Telnet traffic. Packets received on a Layer 2 (VLAN) interface destined for the VRRP virtual IP address terminates on the master router.

VRRP Benefits

The benefits of VRRP are as follows:

- Redundancy—Enables you to configure multiple routers as the default gateway router, which reduces the possibility of a single point of failure in a network.

- Load sharing—Allows traffic to and from LAN clients to be shared by multiple routers. The traffic load is shared more equitably among available routers.

- Multiple VRRP groups—Supports up to 255 VRRP groups on a router physical interface if the platform supports multiple MAC addresses. Multiple VRRP groups enable you to implement redundancy and load sharing in your LAN topology.

- Multiple IP addresses—Allows you to manage multiple IP addresses, including secondary IP addresses. If you have multiple subnets configured on an Ethernet interface, you can configure VRRP on each subnet.

- Preemption—Enables you to preempt a backup router that has taken over for a failing master with a higher priority backup router that has become available.

- Advertisement protocol—Uses a dedicated Internet Assigned Numbers Authority (IANA) standard multicast address (224.0.0.18) for VRRP advertisements. This addressing scheme minimizes the number of routers that must service the multicasts and allows test equipment to accurately identify VRRP packets on a segment. IANA has assigned the IP protocol number 112 to VRRP.

- VRRP tracking—Ensures that the best VRRP router is the master for the group by altering VRRP priorities based on interface states.

Multiple VRRP Groups

You can configure up to 255 VRRP groups on a physical interface. The number of VRRP groups that a router interface can support depends on the following factors:

- Router processing capability

- Router memory capability

In a topology where multiple VRRP groups are configured on a router interface, the interface can act as a master for one VRRP group and as a backup for one or more other VRRP groups.

Figure 20-2 shows a LAN topology in which VRRP is configured so that Routers A and B share the traffic to and from clients 1 through 4. Routers A and B act as backups to each other if either router fails.

Figure 20-2 Load Sharing and Redundancy VRRP Topology

This topology contains two virtual IP addresses for two VRRP groups that overlap. For VRRP group 1, Router A is the owner of IP address 10.0.0.1 and is the master. Router B is the backup to Router A. Clients 1 and 2 are configured with the default gateway IP address of 10.0.0.1.

For VRRP group 2, Router B is the owner of IP address 10.0.0.2 and is the master. Router A is the backup to router B. Clients 3 and 4 are configured with the default gateway IP address of 10.0.0.2.

VRRP Router Priority and Preemption

An important aspect of the VRRP redundancy scheme is the VRRP router priority because the priority determines the role that each VRRP router plays and what happens if the master router fails.

If a VRRP router owns the virtual IP address and the IP address of the physical interface, this router functions as the master. The priority of the master is 255.

Priority also determines if a VRRP router functions as a backup router and the order of ascendancy to becoming a master if the master fails.

For example, if Router A, the master in a LAN topology, fails, VRRP must determine if backups B or C should take over. If you configure Router B with priority 101 and Router C with the default priority of 100, VRRP selects Router B to become the master because it has the higher priority. If you configure routers B and C with the default priority of 100, VRRP selects the backup with the higher IP address to become the master.

VRRP uses preemption to determine what happens after a VRRP backup router becomes the master. With preemption enabled by default, VRRP switches to a backup if that backup comes online with a priority higher than the new master. For example, if Router A is the master and fails, VRRP selects Router B (next in order of priority). If Router C comes online with a higher priority than Router B, VRRP selects Router C as the new master, even though Router B has not failed.

If you disable preemption, VRRP switches only if the original master recovers or the new master fails.

vPC and VRRP

VRRP interoperates with virtual port channels (vPCs). vPCs allow links that are physically connected to two different Cisco Nexus 7000 series devices to appear as a single port channel by a third device. See the Cisco Nexus 7000 Series NX-OS Layer 2 Switching Configuration Guide, Release 5.x, for more information on vPCs.

vPC forwards traffic through both the master VRRP router as well as the backup VRRP router. See the “Configuring VRRP Priority” section.

Note You should configure VRRP on the primary vPC peer device as active and VRRP on the vPC secondary device as standby.

VRRP Advertisements

The VRRP master sends VRRP advertisements to other VRRP routers in the same group. The advertisements communicate the priority and state of the master. Cisco NX-OS encapsulates the VRRP advertisements in IP packets and sends them to the IP multicast address assigned to the VRRP group. Cisco NX-OS sends the advertisements once every second by default, but you can configure a different advertisement interval.

VRRP Authentication

VRRP supports the following authentication functions:

- No authentication

- Plain text authentication

VRRP rejects packets in any of the following cases:

- The authentication schemes differ on the router and in the incoming packet.

- Text authentication strings differ on the router and in the incoming packet.

VRRP Tracking

VRRP supports the following two options for tracking:

- Native interface tracking— Tracks the state of an interface and uses that state to determine the priority of the VRRP router in a VRRP group. The tracked state is down if the interface is down or if the interface does not have a primary IP address.

- Object tracking—Tracks the state of a configured object and uses that state to determine the priority of the VRRP router in a VRRP group. See Chapter 21, “Configuring Object Tracking” for more information on object tracking.

If the tracked state (interface or object) goes down, VRRP updates the priority based on what you configure the new priority to be for the tracked state. When the tracked state comes up, VRRP restores the original priority for the virtual router group.

For example, you may want to lower the priority of a VRRP group member if its uplink to the network goes down so another group member can take over as master for the VRRP group. See the “Configuring VRRP Interface State Tracking” section for more information.

Note VRRP does not support Layer 2 interface tracking.

BFD

This feature supports bidirectional forwarding detection (BFD). BFD is a detection protocol that provides fast-forwarding and path-failure detection times. BFD provides subsecond failure detection between two adjacent devices and can be less CPU-intensive than protocol hello messages because some of the BFD load can be distributed onto the data plane on supported modules. See the Cisco Nexus 7000 Series NX-OS Interfaces Configuration Guide, Release 5.x, for more information.

High Availability

VRRP supports high availability through stateful restarts and stateful switchovers. A stateful restart occurs when the VRRP process fails and is restarted. Stateful switchover occurs when the active supervisor switches to the standby supervisor. Cisco NX-OS applies the run-time configuration after the switchover.

Virtualization Support

VRRP supports virtual routing and forwarding (VRF) instances. VRF exists within virtual device contexts (VDCs). By default, Cisco NX-OS places you in the default VDC and default VRF unless you specifically configure another VDC and VRF.

If you change the VRF membership of an interface, Cisco NX-OS removes all Layer 3 configurations, including VRRP.

For more information, see the Cisco Nexus 7000 Series NX-OS Virtual Device Context Configuration Guide, Release 5.x, and see Chapter14, “Configuring Layer 3 Virtualization”

Licensing Requirements for VRRP

The following table shows the licensing requirements for this feature:

Product

License Requirement

Cisco NX-OS

VRRP requires no license. Any feature not included in a license package is bundled with the Cisco NX-OS system images and is provided at no extra charge to you. For a complete explanation of the Cisco NX-OS licensing scheme, see the Cisco NX-OS Licensing Guide.

Guidelines and Limitations for VRRP

VRRP has the following configuration guidelines and limitations:

- You cannot configure VRRP on the management interface.

- When VRRP is enabled, you should replicate the VRRP configuration across devices in your network.

- We recommend that you do not configure more than one first-hop redundancy protocol on the same interface.

- You must configure an IP address for the interface that you configure VRRP on and enable that interface before VRRP becomes active.

- Cisco NX-OS removes all Layer 3 configurations on an interface when you change the interface VRF membership, port channel membership, or when you change the port mode to Layer 2.

- When you configure VRRP to track a Layer 2 interface, you must shut down the Layer 2 interface and reenable the interface to update the VRRP priority to reflect the state of the Layer 2 interface

- BFD for VRRP can only be configured between two routers..

Default Settings

Table 20-1 lists the default settings for VRRP parameters.

Table 20-1 Default VRRP Parameters

Parameters

Default

advertisement interval

1 seconds

authentication

No authentication

preemption

Enabled

priority

100

VRRP feature

Disabled

Configuring VRRP

This section includes the following topics:

- Enabling the VRRP Feature

- Configuring VRRP Groups

- Configuring VRRP Priority

- Configuring VRRP Authentication

- Configuring Time Intervals for Advertisement Packets

- Disabling Preemption

- Configuring VRRP Interface State Tracking

Note If you are familiar with the Cisco IOS CLI, be aware that the Cisco NX-OS commands for this feature might differ from the Cisco IOS commands that you would use.

Enabling the VRRP Feature

You must globally enable the VRRP feature before you can configure and enable any VRRP groups.

To enable the VRRP feature, use the following command in global configuration mode:

Command

Purpose

feature vrrp

Example:

switch(config)# feature vrrp

Enables VRRP.

To disable the VRRP feature in a VDC and remove all associated configurations, use the following command in global configuration mode:

Command

Purpose

no feature vrrp

Example:

switch(config)# no feature vrrp

Disables the VRRP feature in a VDC.

Configuring VRRP Groups

You can create a VRRP group, assign the virtual IP address, and enable the group.

You can configure one virtual IPv4 address for a VRRP group. By default, the master VRRP router drops the packets addressed directly to the virtual IP address because the VRRP master is only intended as a next-hop router to forward packets. Some applications require that Cisco NX-OS accept packets addressed to the virtual router IP. Use the secondary option to the virtual IP address to accept these packets when the local router is the VRRP master.

Once you have configured the VRRP group, you must explicitly enable the group before it becomes active.

BEFORE YOU BEGIN

Ensure that you are in the correct VDC (or use the switchto vdc command).

Ensure that you configure an IP address on the interface (see the “Configuring IPv4 Addressing” section).

SUMMARY STEPS

1. configure terminal

2. interface interface-type slot/port

3. vrrp number

4. address ip-address [secondary]

5. no shutdown

6. (Optional) show vrrp

7. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

interface interface-type slot/port

Example:

switch(config)#

switch(config-if)# interface ethernet 2/1

Enters interface configuration mode.

Step 3

vrrp number

Example:

switch(config-if)# vrrp 250

switch(config-if-vrrp)#

Creates a virtual router group. The range is from 1 to 255.

Step 4

address ip-address [secondary]

Example:

switch(config-if-vrrp)# address 192.0.2.8

Configures the virtual IPv4 address for the specified VRRP group. This address should be in the same subnet as the IPv4 address of the interface.

Use the secondary option only if applications require that VRRP routers accept the packets sent to the virtual router's IP address and deliver to applications.

Step 5

no shutdown

Example:

switch(config-if-vrrp)# no shutdown

switch(config-if-vrrp)#

Enables the VRRP group. Disabled by default.

Step 6

show vrrp

Example:

switch(config-if-vrrp)# show vrrp

(Optional) Displays VRRP information.

Step 7

copy running-config startup-config

Example:

switch(config-if-vrrp)# copy running-config startup-config

(Optional) Saves this configuration change.

Configuring VRRP Priority

The valid priority range for a virtual router is from 1 to 254 (1 is the lowest priority and 254 is the highest). The default priority value for backups is 100. For devices whose interface IP address is the same as the primary virtual IP address (the master), the default value is 255.

If you configure VRRP on a vPC-enabled interface, you can optionally configure the upper and lower threshold values to control when to fail over to the vPC trunk. If the backup router priority falls below the lower threshold, VRRP sends all backup router traffic across the vPC trunk to forward through the master VRRP router. VRRP maintains this scenario until the backup VRRP router priority increases above the upper threshold.

BEFORE YOU BEGIN

You must enable VRRP (see the “Configuring VRRP” section).

Ensure that you have configured an IP address on the interface (see the “Configuring IPv4 Addressing” section).

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. interface interface-type slot/port

3. vrrp number

4. shutdown

5. priority level [forwarding-threshold lower lower-value upper upper-value]

6. no shutdown

7. (Optional) show vrrp

8. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

interface interface-type slot/port

Example:

switch(config)# interface ethernet 2/1

switch(config-if)#

Enters interface configuration mode.

Step 3

vrrp number

Example:

switch(config-if)# vrrp 250

switch(config-if-vrrp)#

Creates a virtual router group.

Step 4

shutdown

Example:

switch(config-if-vrrp)# shutdown

switch(config-if-vrrp)#

Disables the VRRP group. Disabled by default.

Step 5

priority level [forwarding-threshold lower lower-value upper upper-value]

Example:

switch(config-if-vrrp)# priority 60 forwarding-threshold lower 40 upper 50

Sets the priority level used to select the active router in an VRRP group. The level range is from 1 to 254. The default is 100 for backups and 255 for a master that has an interface IP address equal to the virtual IP address.

Optionally, sets the upper and lower threshold values used by vPC to determine when to fail over to the vPC trunk. The lower-value range is from 1 to 255. The default is 1. The upper-value range is from 1 to 255. The default is 255.

Step 6

no shutdown

Example:

switch(config-if-vrrp)# no shutdown

switch(config-if-vrrp)#

Enables the VRRP group. Disabled by default.

Step 7

show vrrp

Example:

switch(config-if-vrrp)# show vrrp

(Optional) Displays a summary of VRRP information.

Step 8

copy running-config startup-config

Example:

switch(config-if-vrrp)# copy running-config startup-config

(Optional) Saves this configuration change.

Configuring VRRP Authentication

You can configure simple text authentication for a VRRP group.

BEFORE YOU BEGIN

Ensure that the authentication configuration is identical for all VRRP devices in the network.

Ensure that you have enabled VRRP (see the “Configuring VRRP” section).

Ensure that you have configured an IP address on the interface (see the “Configuring IPv4 Addressing” section).

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. interface interface-type slot/port

3. vrrp number

4. shutdown

5. authentication text password

6. no shutdown

7. (Optional) show vrrp

8. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

interface interface-type slot/port

Example:

switch(config)# interface ethernet 2/1

switch(config-if)#

Enters interface configuration mode.

Step 3

vrrp number

Example:

switch(config-if)# vrrp 250

switch(config-if-vrrp)#

Creates a virtual router group.

Step 4

shutdown

Example:

switch(config-if-vrrp)# shutdown

switch(config-if-vrrp)#

Disables the VRRP group. Disabled by default.

Step 5

authentication text password

Example:

switch(config-if-vrrp)# authentication text aPassword

Assigns the simple text authentication option and specifies the keyname password. The keyname range is from 1 to 255 characters. We recommend that you use at least 16 characters. The text password is up to eight alphanumeric characters.

Step 6

no shutdown

Example:

switch(config-if-vrrp)# no shutdown

switch(config-if-vrrp)#

Enables the VRRP group. Disabled by default.

Step 7

show vrrp

Example:

switch(config-if-vrrp)# show vrrp

(Optional) Displays a summary of VRRP information.

Step 8

copy running-config startup-config

Example:

switch(config-if-vrrp)# copy running-config startup-config

(Optional) Saves this configuration change.

Configuring Time Intervals for Advertisement Packets

You can configure the time intervals for advertisement packets.

BEFORE YOU BEGIN

You must enable VRRP (see the “Configuring VRRP” section).

Ensure that you have configured an IP address on the interface (see the “Configuring IPv4 Addressing” section).

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. interface interface-type slot/port

3. vrrp number

4. shutdown

5. advertisement-interval seconds

6. no shutdown

7. (Optional) show vrrp

8. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

interface interface-type slot/port

Example:

switch(config)# interface ethernet 2/1

switch(config-if)#

Enters interface configuration mode.

Step 3

vrrp number

Example:

switch(config-if)# vrrp 250

switch(config-if-vrrp)#

Creates a virtual router group.

Step 4

shutdown

Example:

switch(config-if-vrrp)# shutdown

switch(config-if-vrrp)#

Disables the VRRP group. Disabled by default.

Step 5

advertisement-interval seconds

Example:

switch(config-if-vrrp)# advertisement-interval 15

Sets the interval time in seconds between sending advertisement frames. The range is from 1 to 255. The default is 1 second.

Step 6

no shutdown

Example:

switch(config-if-vrrp)# no shutdown

switch(config-if-vrrp)#

Enables the VRRP group. Disabled by default.

Step 7

show vrrp

Example:

switch(config-if-vrrp)# show vrrp

(Optional) Displays a summary of VRRP information.

Step 8

copy running-config startup-config

Example:

switch(config-if-vrrp)# copy running-config startup-config

(Optional) Saves this configuration change.

Disabling Preemption

You can disable preemption for a VRRP group member. If you disable preemption, a higher-priority backup router does not take over for a lower-priority master router. Preemption is enabled by default.

BEFORE YOU BEGIN

You must enable VRRP (see the “Configuring VRRP” section).

Ensure that you have configured an IP address on the interface (see the “Configuring IPv4 Addressing” section).

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. interface interface-type slot/port

3. vrrp number

4. shutdown

5. no preempt

6. no shutdown

7. (Optional) show vrrp

8. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

interface interface-type slot/port

Example:

switch(config)# interface ethernet 2/1

switch(config-if)#

Enters interface configuration mode.

Step 3

vrrp number

Example:

switch(config-if)# vrrp 250

switch(config-if-vrrp)#

Creates a virtual router group.

Step 4

no shutdown

Example:

switch(config-if-vrrp)# no shutdown

Enables the VRRP group. Disabled by default.

Step 5

no preempt

Example:

switch(config-if-vrrp)# no preempt

Disables the preempt option and allows the master to remain when a higher-priority backup appears.

Step 6

no shutdown

Example:

switch(config-if-vrrp)# no shutdown

Enables the VRRP group. Disabled by default.

Step 7

show vrrp

Example:

switch(config-if-vrrp)# show vrrp

(Optional) Displays a summary of VRRP information.

Step 8

copy running-config startup-config

Example:

switch(config-if-vrrp)# copy running-config startup-config

(Optional) Saves this configuration change.

Configuring VRRP Interface State Tracking

Interface state tracking changes the priority of the virtual router based on the state of another interface in the device. When the tracked interface goes down or the IP address is removed, Cisco NX-OS assigns the tracking priority value to the virtual router. When the tracked interface comes up and an IP address is configured on this interface, Cisco NX-OS restores the configured priority to the virtual router (see the“Configuring VRRP Priority” section).

Note For interface state tracking to function, you must enable preemption on the interface.

Note VRRP does not support Layer 2 interface tracking.

BEFORE YOU BEGIN

You must enable VRRP (see the “Configuring VRRP” section).

Ensure that you have configured an IP address on the interface (see the “Configuring IPv4 Addressing” section).

Ensure that you have enabled the virtual router (see the “Configuring VRRP Groups” section).

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. interface interface-type slot/port

3. vrrp number

4. shutdown

5. track interface type number priority value

6. no shutdown

7. (Optional) show vrrp

8. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

interface interface-type slot/port

Example:

switch(config)# interface ethernet 2/1

switch(config-if)#

Enters interface configuration mode.

Step 3

vrrp number

Example:

switch(config-if)# vrrp 250

switch(config-if-vrrp)#

Creates a virtual router group.

Step 4

shutdown

Example:

switch(config-if-vrrp)# shutdown

switch(config-if-vrrp)#

Disables the VRRP group. Disabled by default.

Step 5

track interface type number priority value

Example:

switch(config-if-vrrp)# track interface ethernet 2/10 priority 254

Enables interface priority tracking for a VRRP group. The priority range is from 1 to 254.

Step 6

no shutdown

Example:

switch(config-if-vrrp)# no shutdown

switch(config-if-vrrp)#

Enables the VRRP group. Disabled by default.

Step 7

show vrrp

Example:

switch(config-if-vrrp)# show vrrp

(Optional) Displays a summary of VRRP information.

Step 8

copy running-config startup-config

Example:

switch(config-if-vrrp)# copy running-config startup-config

(Optional) Saves this configuration change.

Verifying the VRRP Configuration

To display VRRP configuration information, perform one of the following tasks:

Command

Purpose

show vrrp

Displays the VRRP status for all groups.

show vrrp vr group-number

Displays the VRRP status for a VRRP group.

show interface interface-type

Displays the virtual router configuration for an interface.

Monitoring VRRP Statistics

Command

Purpose

show vrrp statistics

Displays the VRRP statistics.

Use the clear vrrp statistics command to clear all the VRRP statistics for all interfaces in the device.

Use the clear vrrp vr command to clear the IPv4 VRRP statistics for a specified interface.

Use the clear vrrp ipv4 command to clear all the statistics for the specified IPv4 virtual router.

Configuration Examples for VRRP

In this example, Router A and Router B each belong to three VRRP groups. In the configuration, each group has the following properties:

- Group 1:

– Virtual IP address is 10.1.0.10.

– Router A will become the master for this group with priority 120.

– Advertising interval is 3 seconds.

– Preemption is enabled.

- Group 5:

– Router B will become the master for this group with priority 200.

– Advertising interval is 30 seconds.

– Preemption is enabled.

- Group 100:

– Router A will become the master for this group first because it has a higher IP address (10.1.0.2).

– Advertising interval is the default 1 second.

– Preemption is disabled.

Router A

interface ethernet 1/0

ip address 10.1.0.2/16

no shutdown

vrrp 1

priority 120

authentication text cisco

advertisement-interval 3

address 10.1.0.10

no shutdown

vrrp 5

priority 100

advertisement-interval 30

address 10.1.0.50

no shutdown

vrrp 100

no preempt

address 10.1.0.100

no shutdown

Router B

interface ethernet 1/0

ip address 10.2.0.1/2

no shutdown

vrrp 1

priority 100

authentication text cisco

advertisement-interval 3

address 10.2.0.10

no shutdown

vrrp 5

priority 200

advertisement-interval 30

address 10.2.0.50

no shutdown

vrrp 100

no preempt

address 10.2.0.100

no shutdown

Additional References

For additional information related to implementing VRRP, see the following sections:

- Related Documents

Related Documents

Related Topic

Document Title

Configuring the gateway load balancing protocol

Chapter 18, “Configuring GLBP”

Configuring the hot standby routing protocol

Chapter 19, “Configuring HSRP”

VRRP CLI commands

Cisco Nexus 7000 Series NX-OS Unicast Routing Command Reference, Release 5.x

Configuring high availability

Cisco Nexus 7000 Series NX-OS High Availability and Redundancy Guide, Release 5.x

Feature History for VRRP

Table 20-2 lists the release history for this feature.

Table 20-2 Feature History for VRRP

Feature Name

Releases

Feature Information

BFD for VRRP

5.2(1)

Added support for BFD.

VRRP priority thresholds

4.2(1)

Added support for priority thresholds and vPC.

VRRP object tracking

4.2(1)

Added support for tracking multiple object types in VRRP.

VRRP

4.0(1)

Configuring WCCPv2

This chapter describes how to configure the Web Cache Communication Protocol version 2 (WCCPv2) on the Cisco NX-OS device.

This chapter includes the following sections:

- Information About WCCPv2

- Licensing Requirements for WCCPv2

- Prerequisites for WCCPv2

- Guidelines and Limitations for WCCPv2

- Default Settings

- Configuring WCCPv2

- Verifying the WCCPv2 Configuration

- Configuration Examples for WCCPv2

- Additional References

- Feature History for WCCPv2

Information About WCCPv2

WCCPv2 specifies interactions between one or more Cisco NX-OS routers and one or more cache engines. WCCPv2 transparently redirects selected types of traffic through a group of routers. The selected traffic is redirected to a group of cache engines to optimize resource usage and lower response times.

Cisco NX-OS does not support WCCPv1.

This section includes the following topics:

- WCCPv2 Overview

- WCCPv2 Authentication

- Redirection Method

- Packet Return Method

- High Availability for WCCPv2

- Virtualization Support for WCCPv2

WCCPv2 Overview

WCCPv2 enables the Cisco NX-OS router to transparently redirect packets to cache engines. WCCPv2 does not interfere with normal router operations. Using WCCPv2, the router can redirect requests on configured interfaces to cache engines rather than to intended host sites. With WCCPv2, the router can balance traffic loads across a cluster of cache engines (cache cluster) and ensure fault-tolerant and fail-safe operation in the cluster. As you add or delete cache engines from a cache cluster, WCCPv2 dynamically redirects the packets to the currently available cache engines.

WCCPv2 accepts the traffic at the cache engine and establishes the connection with the traffic originator (the client). The cache engine acts as if it were the original destination server. If the requested object is not available on the cache engine, the cache engine establishes its own connection out to the original destination server to retrieve the object.

WCCPv2 communicates between routers and cache engines on UDP port 2048.

By allowing a cache cluster to connect to multiple routers, WCCPv2 provides redundancy and a distributed architecture for instances when a cache engine must connect to many interfaces. In addition, WCCPv2 allows you to keep all the cache engines in a single cluster, which avoids the unnecessary duplication of web pages across several clusters.

This section includes the following topics:

- WCCPv2 Service Types

- Service Groups

- Service Group Lists

- WCCPv2 Designated Cache Engine

- Redirection

WCCPv2 Service Types

A service is a defined traffic type that the router redirects to a cache engine with the WCCPv2 protocol.

You can configure the router to run one of the following cache-related services:

- Well-known —The router and the cache engine know the traffic type, for example the web cache service on TCP port 80 for HTTP.

- Dynamic service—A service in which the cache engine describes the type of redirected traffic to the router.

Service Groups

A service group is a subset of cache engines within a cluster and the routers connected to the cluster that are running the same service. Figure 5-1 shows a service group within a cache cluster. The cache engines and the routers can be a part of multiple service groups.

Figure 5-1 WCCPv2 Cache Cluster and Service Group

You can configure a service group as open or closed. An open service group forwards traffic without redirection if there is no cache engine to redirect the traffic to. A closed service group drops traffic if there is no cache engine to redirect the traffic to.

The service group defines the traffic that is redirected to individual cache engines in that service group. The service group definition consists of the following:

- Service ID (0–255)

- Service Type

- Priority of the service group

- Protocol (TCP or UDP) of redirected traffic

- Service flags

- Up to eight TCP or UDP port numbers (either all source or all destination port numbers)

Service Group Lists

WCCPv2 requires that each cache engine be aware of all the routers in the service group. You can configure a list of router addresses for each of the routers in the group on each cache engine.

The following sequence of events details how WCCPv2 configuration works:

Step 1 You configure each cache engine with a list of routers.

Step 2 Each cache engine announces its presence and generates a list of all routers with which it has established communications.

Step 3 The routers reply with their view (list) of cache engines in the group.

The cache engines and routers exchange control messages every 10 seconds by default.

WCCPv2 Designated Cache Engine

WCCPv2 designates one cache engine as the lead. If there is a group of cache engines, the one seen by all routers and the one that has the lowest IP address becomes the designated cache engine. The designated cache engine determines how traffic should be allocated across cache engines. The traffic assignment method is passed to the entire service group from the designated cache engine so that the routers of the group can redirect the packets and the cache engines of the group can manage their traffic load better.

Cisco NX-OS uses the mask method to assign traffic. The designated cache engine assigns the mask and value sets to the router in the WCCP Redirect Assignment message. The router matches these mask and value sets to the source IP address, destination IP address, source port, and destination port of each packet. The router redirects the packet to the cache engine if the packet matches an assigned mask and value set. If the packet does not match an assigned mask and value set, the router forwards the packet without any redirection.

Redirection

You can use an IP access list as a redirect list to specify a subset of traffic to redirect with WCCPv2. You can apply this access list for ingress or egress traffic on an interface. Figure 5-2 shows how redirection applies to ingress or egress traffic.

Figure 5-2 WCCP Redirection

You can also exclude ingress traffic on an interface but allow egress redirection on that interface.

WCCPv2 Authentication

WCCPv2 can authenticate a device before it adds that device to the service group. Message Digest (MD5) authentication allows each WCCPv2 service group member to use a secret key to generate a keyed MD5 digest string that is part of the outgoing packet. At the receiving end, a keyed digest of an incoming packet is generated. If the MD5 digest within the incoming packet does not match the generated digest, WCCP ignores the packet.

WCCPv2 rejects packets in any of the following cases:

- The authentication schemes differ on the router and in the incoming packet.

- The MD5 digests differ on the router and in the incoming packet.

Redirection Method

WCCPv2 negotiates the packet redirection method between the router and the cache engine. Cisco NX-OS uses this traffic redirection method for all cache engines in a service group.

WCCPv2 redirects packets using the following forwarding method:

- Layer 2 Destination MAC rewrite—WCCPv2 replaces the destination MAC address of the packet with the MAC address of the cache engine that needs to handle the packet. The cache engine and the router must be adjacent to Layer 2.

You can also configure an access control list (ACL), called a redirect list, for a WCCPv2 service group. This ACL can either permit a packet to go through the WCCPv2 redirection process or deny the WCCP redirection and send the packet through the normal packet forwarding procedure.

Packet Return Method

WCCPv2 filters packets to determine which redirected packets have been returned from the cache engine and which packets have not. WCCPv2 does not redirect the returned packets, because the cache engine has determined that these packets should not be cached. WCCPv2 returns packets that the cache engine does not service to the router that transmitted them.

A cache engine may return a packet for one of the following reasons:

- The cache engine is overloaded and cannot service the packets.

- The cache engine is filtering certain conditions that make caching packets counterproductive, for example, when IP authentication has been turned on.

WCCPv2 negotiates the packet return method between the router and the cache engine. Cisco NX-OS uses this traffic return method for all cache engines in a service group.

WCCPv2 returns packets using the following forwarding method:

- Destination MAC rewrite—WCCPv2 replaces the destination MAC address of the packet with the MAC address of the router that originally redirected the packet. The cache engine and the router must be adjacent to Layer 2.

High Availability for WCCPv2

WCCPv2 supports stateful restarts and stateful switchovers. A stateful restart occurs when the WCCPv2 process fails and is restarted. A stateful switchover occurs when the active supervisor switches to the standby supervisor. Cisco NX-OS applies the running configuration after a switchover.

Virtualization Support for WCCPv2

WCCPv2 supports virtual routing and forwarding (VRF) instances. VRFs exist within virtual device contexts (VDCs). By default, Cisco NX-OS places you in the default VDC and default VRF unless you specifically configure another VDC and VRF.

WCCP redirection occurs within a VRF. You must configure the WCCP cache engine so that the forward and return traffic to and from the cache engine occurs from interfaces that are a part of the same VRF.

The VRF used for the WCCP on an interface should match the VRF configured on that interface.

If you change the VRF membership of an interface, Cisco NX-OS removes all layer 3 configuration, including WCCPv2.

For more information, see the Cisco Nexus 7000 Series NX-OS Virtual Device Context Configuration Guide, Release 5.x, and see Chapter14, “Configuring Layer 3 Virtualization”

WCCPv2 Error Handling for SPM Operations

The Service Policy Manager (SPM) supervisor component acts as a data path manager for the WCCP Manager. The WCCP manager is shielded from the underlying platform specifics by the SPM and is portable to platform variations. The WCCP manager has a set of SPM APIs to pass the configurations that are mapped and programmed in the hardware. These APIs can process and parse the application data that is implemented and maintained in one single handler.

The interface redirects that failed to be programmed by the SPM are stored until there is a service group configuration change through the CLI or an RA message. The WCCP manager retries programming policies that failed previously.

The WCCP manager sends policy updates to the SPM in intervals to program TCAM entries in the hardware. These policy updates can be triggered by the CLI or through RA (Redirect-Assign) messages. When the WCCP is notified of an SPM error, a syslog message appears.

Support for Configurable Service Group Timers

A single WCCP service group can have up to 32 routers and 32 cache engines. The cache engine uses a WCCP Here I Am (HIA) message to send its properties to the router. HIA messages are sent every 10 seconds by default. You must configure the HIA timer for every service group. This timer is used to determine the HIA timeout for all clients on the service group.

Licensing Requirements for WCCPv2

The following table shows the licensing requirements for this feature:

Product

License Requirement

Cisco NX-OS

WCCPv2 requires no license. Any feature not included in a license package is bundled with the Cisco NX-OS system images and is provided at no extra charge to you. For a complete explanation of the Cisco NX-OS licensing scheme, see the Cisco NX-OS Licensing Guide.

Prerequisites for WCCPv2

WCCPv2 has the following prerequisites:

- You must globally enable the WCCPv2 feature (see the “Enabling WCCPv2” section).

- You can only configure WCCPv2 on Layer 3 or VLAN interfaces (see the Cisco Nexus 7000 Series NX-OS Interfaces Configuration Guide, Release 5.x ).

- If you configure VDCs, install the Advanced Services license and enter the desired VDC (see the Cisco Nexus 7000 Series NX-OS Virtual Device Context Configuration Guide, Release 5.x).

Guidelines and Limitations for WCCPv2

WCCPv2 has the following configuration guidelines and limitations:

- A WCCPv2 service group supports up to 32 routers and 32 cache engines.

- All cache engines in a cluster must include all routers that service the cluster in its configuration. If a cache engine within a cluster does not include one or more of the routers in its configuration, the service group detects the inconsistency and the cache engine is not allowed to operate within the service group.

- The cache engine cannot be on the same SVI with a redirect out statement.

- WCCPv2 works with IPv4 networks only.

- Cisco NX-OS removes all Layer 3 configuration on an interface when you change the VDC, interface VRF membership, port-channel membership, or the port mode to Layer 2.

- Wildcard masks are not supported for the WCCPv2 redirect list.

- Beginning with Cisco NX-OS Release 5.2(4), policy-based routing and WCCPv2 are supported on the same interface. However, policy-based routing with statistics and WCCPv2 is supported on the same interface only if bank chaining is disabled.

- Cisco NX-OS does not support WCCPv2 on tunnel interfaces.

- WCCP requires the client, server, and WCCP client to be on separate interfaces. If you migrate a topology from a Cisco Catalyst 6500 Series switch deployment, it might not be supported.

- M1 Series modules support WCCPv2. F1 Series modules do not support WCCPv2.

Default Settings

Table 5-1 lists the default settings for WCCPv2 parameters.

Table 5-1 Default WCCPv2 Parameters

Parameters

Default

Authentication

No authentication

WCCPv2

Disable

Configuring WCCPv2

To configure WCCPv2, follow these steps:

Step 1 Enable the WCCPv2 feature. See the “Enabling WCCPv2” section.

Step 2 Configure a service group. See the “Configuring a WCCPv2 Service Group” section.

Step 3 Apply WCCPv2 redirection to an interface. See the “Applying WCCPv2 Redirection to an Interface” section.

This section includes the following topics:

- Enabling WCCPv2

- Configuring a WCCPv2 Service Group

- Applying WCCPv2 Redirection to an Interface

- Configuring WCCPv2 in a VRF

Note If you are familiar with the Cisco IOS CLI, be aware that the Cisco NX-OS commands for this feature might differ from the Cisco IOS commands that you would use.

Enabling WCCPv2

You must enable the WCCPv2 feature before you can configure WCCPv2.

BEFORE YOU BEGIN

Ensure that you are in the correct VDC (or use the switchto vdc command).

DETAILED STEPS

To enable the WCCPv2 feature, use the following command in global configuration mode:

Command

Purpose

feature wccp

Example:

switch(config)# feature wccp

Enables the WCCPv2 feature in a VDC.

To disable the WCCPv2 feature in a VDC and remove all associated configuration, use the following command in global configuration mode:

Command

Purpose

no feature wccp

Example:

switch(config)# no feature wccp

Disables the WCCPv2 feature in a VDC and removes all associated configuration.

Configuring a WCCPv2 Service Group

You can configure a WCCPv2 service group. You can optionally configure the following:

- Open or closed mode (with a service list)—Controls the traffic type that this service group handles.

- WCCPv2 authentication—Authenticates the WCCPv2 messages using an MD5 digest. WCCPv2 discards messages that fail authentication.

Note You must configure the same authentication on all members of the WCCPv2 service group.

- Redirection limits—Controls the traffic that is redirected to the cache engine.

Closed mode for dynamic service groups requires a service list ACL that specifies the protocol and port information that is used for the service group. If there are no members in the service group, packets matching the service-list ACL are dropped.

Note The service-list keyword ACL must have only protocol and port information. To restrict traffic that is considered for redirection, use the redirect-list keyword.

Note You must enter the ip wccp command with all your required parameters. Any subsequent entry of the ip wccp command overwrites the earlier configuration.

BEFORE YOU BEGIN

Ensure that you are in the correct VDC (or use the switchto vdc command).

Enable the WCCPv2 feature (see the “Enabling WCCPv2” section).

DETAILED STEPS

To configure a WCCPv2 service group, use the following command in global configuration mode:

Command

Purpose

ip wccp {service-number | web-cache} [mode {open [redirect-list acl-name] | closed service-list acl-name}][password [0-7] pwstring]

Example:

switch(config)# ip wccp web-cache

Example:

switch(config)# ip wccp 10 password Test1 redirect-list httpTest

Creates an open or closed mode service group. The service list identifies a named extended IP access list that defines the packets that will match the service. This list is required only when the service is defined as closed mode. The service-access-list can be any case-sensitive, alphanumeric string up to 64 characters.

Optional parameters are as follows:

- mode —Configures the service group in open or closed mode. The default is open. For closed mode, use this keyword to configure an IP access list to define the traffic type that matches this service.

- password —Configures MD5 authentication for a service group. Use password 0 pwstring to store the password in clear text. Use password 7 pwstring to store the password in encrypted form. You can use the password 7 keywords for an already encrypted password.

- redirect-list —Configures a global WCCPv2 redirection list for the service group to control the traffic that is redirected to the cache engine.

- service-list —Configures an IP access list that defines the traffic type redirected by the service group.

The service-number range is from 1 to 255. The acl-name can be any case-sensitive, alphanumeric string up to 64 characters. The pwstring can be any case-sensitive, alphanumeric string up to eight characters

Applying WCCPv2 Redirection to an Interface

To apply WCCPv2 redirection on an interface, use the following commands in interface configuration mode:

Command

Purpose

ip wccp service-number redirect {in | out}

Example:

switch(config-if)# ip wccp 10 redirect in

Applies WCCPv2 redirection on the ingress or egress traffic for this interface.

ip wccp web-cache redirect {in | out}

Example:

switch(config-if)# ip wccp web-cache redirect out

Applies WCCPv2 redirection on the ingress or egress web cache traffic for this interface.

ip wccp redirect exclude in

Example:

switch(config-if)# ip wccp redirect exclude in

Excludes ingress traffic from WCCP redirection on this interface.

This example shows how to configure a router to redirect web-related packets without a destination of 19.20.2.1 to the web cache:

switch(config)# access-list 100

switch(config-acl)# deny ip any host 192.0.2.1

switch(config-acl)# permit ip any any

switch(config-acl)# exit

switch(config)# ip wccp web-cache redirect-list 100

switch(config)# interface ethernet 2/1

switch(config-if)# ip wccp web-cache redirect out

Configuring WCCPv2 in a VRF

You can configure WCCPv2 redirection on an interface in a VRF.

Note The WCCPv2 VRF must match the VRF configured on the interface.

SUMMARY STEPS

1. configure terminal

2. vrf-context vrf-name

3. ip wccp {service-number | web-cache} [mode {open [redirect-list acl-name] | closed service-list acl-name}]] [password [0-7] pwstring]

4. (Optional) show ip wccp [vrf vrf-name]

5. (Optional) copy running-config startup-config

DETAILED STEPS

Command

Purpose

Step 1

configure terminal

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

vrf context vrf-name

Example:

switch(config)# vrf context Red

switch(config-vrf)#

Enters VRF configuration mode. The vrf-name can be any case-sensitive, alphanumeric string up to 63 characters.

Step 3

ip wccp {service-number | web-cache} [mode {open [redirect-list acl-name] | closed service-list acl-name}][password [0-7] pwstring]

Example:

switch(config-vrf)# ip wccp 10

Example:

switch(config-vrf)# ip wccp web-cache password Test1 redirect-list httpTest

Creates an open or closed mode service group. The service list identifies a named extended IP access list that defines the packets that matches the service. This list is required only when the service is defined as closed mode.

Optional parameters are as follows:

- mode —Configures the service group in open or closed mode. The default is open. For closed mode, use this keyword to configure an IP access list to define the traffic type that matches this service.

- password —Configures MD5 authentication for a service group. Use password 0 pwstring to store the password in clear text. Use password 7 pwstring to store the password in encrypted form. You can use the password 7 keywords for an already encrypted password.

- redirect-list —Configures a global WCCPv2 redirection list for the service group to control the traffic that is redirected to the cache engine.

- service-list —Configures an IP access list that defines the traffic type redirected by the service group.

The service-number range is from 1 to 255. The acl-name can be any case-sensitive, alphanumeric string up to 64 characters. The pwstring can be any case-sensitive, alphanumeric string up to eight characters

Step 4

show ip wccp [vrf vrf-name]

Example:

switch(config-vrf)# show ip wccp vrf Red

(Optional) Displays information about WCCPv2. The vrf-name can be any case-sensitive, alphanumeric string up to 64 characters.

Step 5

copy running-config startup-config

Example:

switch(config-vrf)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to configure WCCPv2 in VRF Red on interface Ethernet 2/1:

switch# configure terminal

switch(config)# vrf context Red

switch(config-vrf)# ip wccp web-cache password Test1 redirect-list httpTest

switch(config-vrf)# interface ethernet 2/1

switch(config-if)# vrf member Red

switch(config-if)# ip wccp web-cache redirect out

Verifying the WCCPv2 Configuration

To display the WCCPv2 configuration, perform one of the following tasks:

Command

Purpose

show ip wccp [vrf vrf-name] [service-number | web-cache]

Displays the WCCPv2 status for all groups or one group in a VRF.

show ip interface [ethernet-number]

Displays the WCCPv2 interface information.

show ip wccp [service-number | web-cache]

Displays the WCCPv2 service group status.

show ip wccp [service-number | web-cache] detail

Displays the clients in a WCCPv2 service group.

show ip wccp [service-number | web-cache] mask

Displays the WCCPv2 mask assignment.

show ip wccp [service-number | web-cache] service

Displays the WCCPv2 service group definition.

show ip wccp [service-number | web-cache] view

Displays the WCCPv2 group membership.

To clear WCCPv2 statistics, use the clear ip wccp command.

Configuration Examples for WCCPv2

This example shows how to configure WCCPv2 authentication on router redirect web-related packets without a destination of 192.0.2.1 to the web cache:

access-list 100

deny ip any host 192.0.2.1

permit ip any any

feature wccp

ip wccp web-cache password 0 Test1 redirect-list 100

interface ethernet 1/2

ip wccp web-cache redirect out

no shutdown

Note See the Cisco Nexus 7000 Series NX-OS Security Configuration Guide, Release 5.x, for information about IP access lists.

Additional References

For additional information related to implementing WCCPv2, see the following sections:

- Related Documents

- Standards

Related Documents

Related Topic

Document Title

WCCPv2 CLI commands

Cisco Nexus 7000 Series NX-OS Unicast Routing Command Reference, Release 5.x

Standards

Standards

Title

No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.

—

Feature History for WCCPv2

Table 5-2 lists the release history for this feature.

Table 5-2 Feature History for WCCPv2

Feature Name

Releases

Feature Information

WCCPv2

5.2(4)

Added support for policy-based routing and WCCPv2 on the same interface if bank chaining is disabled.

WCCPv2 Error Handling for SPM Operations

5.1(1)

This feature was introduced.

WCCPv2

4.2(1)

This feature was introduced.