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

OSPFv3 is an IETF link-state protocol (see Overview). 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 Configuring OSPFv2.

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, Cisco NX-OS does not support RFC 6506 and provides only partial support for RFC 4552, beginning with Cisco NX-OS release 7.0(3)I3(1).

  • 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 configured dead 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)

  • Authentication

  • 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. The following figure 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 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 areas. 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 the following figure).

Figure 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 OSPFv3 Areas, 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.

LSA Types

Following table shows the LSA types supported by Cisco NX-OS.

Table 1. LSA Types

Name

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 Designated Routersflooded 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.

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.

Following figure 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 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. Following figure shows a virtual link that connects Area 3 to the backbone area through Area 5.

Figure 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 supports high-availability. If a Cisco NX-OS system experiences a cold reboot, the network stops forwarding traffic to the system and removes the system from the network topology. In this scenario, OSPFv3 experiences a stateless restart, and removes all neighbor adjacencies on the local system. Cisco NX-OS applies the startup configuration and OSPFv3 rediscovers the neighbors and establishes the adjacencies again.

OSPFv3 automatically restarts if the process experiences problems. After the restart, OSPFv3 initiates a graceful restart so that the platform is not taken out of the network topology. If you manually restart OSPF, it performs a graceful restart, which is similar to a stateful switchover. The running configuration is applied in both cases.

A graceful restart, or nonstop forwarding (NSF), allows OSPFv3 to remain in the data forwarding path through a process restart. When OSPFv3 needs to restart, it first 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 were 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 graceful restart has finished.


Note

If the restarting OSPFv3 interface does not come back up before the end of the grace period, or if the network experiences a topology change, the OSPFv3 neighbors tear down adjacency with the restarting OSPFv3 and treat it as a normal OSPFv3 restart.


Note

You must enable graceful restart to support an in-service software upgrade (ISSU) for OSPFv3. If you disable graceful restart, Cisco NX-OS issues a warning that ISSU cannot be supported with this configuration.

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.

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.

Virtualization Support

OSPFv3 supports virtual routing and forwarding (VRF) instances.

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.

  • You are familiar with IPv6 addressing and basic configuration. See Configuring IPv6 for information on IPv6 routing and addressing.

Guidelines and Limitations for OSPFv3

OSPFv3 has the following configuration guidelines and limitations:

  • 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

Default Settings

Following table lists the default settings for OSPFv3 parameters:

Table 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.

Enabling OSPFv3

You must enable OSPFv3 before you can configure OSPFv3.

Procedure

  Command or Action Purpose

Step 1

configure terminal

Example:

switch# configure terminal
switch(config)#

Enters global configuration mode.

Step 2

feature ospfv3

Example:

switch(config)# feature ospfv3

Enables OSPFv3.

Step 3

(Optional) show feature

Example:

switch(config)# show feature
 (Optional)

Displays enabled and disabled features.

Step 4

(Optional) copy running-config startup-config

Example:

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

Saves this configuration change.

Example

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 ospfv

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.

Procedure

  Command or Action Purpose

Step 1

configure terminal

Example:

switch# configure terminal
switch(config)#

Enters global 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

(Optional) 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

(Optional) show ipv6 ospfv3 instance-tag

Example:

switch(config-router)# show ipv6 ospfv3 201
 (Optional)

Displays OSPFv3 information.

Step 5

(Optional) copy running-config startup-config

Example:

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

Saves this configuration change.

Example

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.

You can configure the following optional parameters for OSPFv3 in router configuration 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

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 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).

Procedure

  Command or Action Purpose

Step 1

configure terminal

Example:

switch# configure terminal
switch(config)#

Enters global 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

(Optional) 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

(Optional) copy running-config startup-config

Example:

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

Saves this configuration change.

Example

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

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.

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 OSPFv3 IPSec Authentication

You can configure OSPFv3 IP security (IPSec) authentication for a process, an area, and/or an interface.

The authentication configuration is inherited from process to area to interface level. If authentication is configured at all three levels, the interface configuration takes precedence over the process and area configurations.

Before you begin

Ensure that you have enabled OSPFv3 (see the Enabling OSPFv3 section).

Procedure

  Command or Action Purpose

Step 1

configure terminal

Example:

switch# configure terminal
switch(config)#

Enters global configuration mode.

Step 2

[no] feature imp

Example:

switch(config)# feature imp

Enables the Internet messaging program (IMP), which is required for OSPFv3 authentication.

Step 3

router ospfv3 instance-tag

Example:

switch(config)# router ospfv3 100
switch(config-router)#

Creates a new OSPFv3 instance with the configured instance tag.

Step 4

exit

Example:

switch(config-router)# exit
switch(config)#

Exits OSPFv3 router configuration mode.

Step 5

authentication ipsec spi spi auth [0 | 3 | 7] key

Example:

switch(config)# authentication ipsec spi 475 md5 11111111111111112222222222222222

Configures OSPFv3 IPSec authentication at the process (or VRF) level.

The spi argument specifies the security parameter index (SPI). The range is from 256 to 4294967295.

The auth argument specifies the type of authentication. The supported values are md5 or sha1.

0 configures the password in cleartext. 3 configures the pass key as 3DES encrypted. 7 configures the key as Cisco type 7 encrypted.

If the cleartext option (0) is used, the key argument must be 32 characters long for md5 or 40 characters long for sha1.

Step 6

Option Description
Command Purpose

area area authentication ipsec spi spi auth [0 | 3 | 7] key

Example:

switch(config)# area 0 authenticationipsec spi 475 md5 11111111111111112222222222222222

Configures OSPFv3 IPSec authentication at the area level.

The spi argument specifies the security parameter index (SPI). The range is from 256 to 4294967295.

The auth argument specifies the type of authentication. The supported values are md5 or sha1.

0 configures the password in cleartext. 3 configures the pass key as 3DES encrypted. 7 configures the key as Cisco type 7 encrypted.

If the cleartext option (0) is used, the key argument must be 32 characters long for md5 or 40 characters long for sha1.

Note

 

Use the area area authentication disable command to disable OSPFv3 IPSec authentication at the area level.

interface interface-type slot/port ospfv3 authentication ipsec spi spi auth [0 | 3 | 7] key

Example:

switch(config)# interface ethernet 1/1 switch(config-if)# ospfv3 authentication ipsec spi 475 md5 11111111111111112222222222222222

Configures OSPFv3 IPSec authentication for the specified interface.

The spi argument specifies the security parameter index (SPI). The range is from 256 to 4294967295.

The auth argument specifies the type of authentication. The supported values are md5 or sha1.

0 configures the password in cleartext. 3 configures the pass key as 3DES encrypted. 7 configures the key as Cisco type 7 encrypted.

If the cleartext option (0) is used, the key argument must be 32 characters long for md5 or 40 characters long for sha1.

Note

 

Use the ospfv3 authentication disable command to disable OSPFv3 IPSec authentication for the specified interface.

Step 7

(Optional) show ospfv3 process

Example:

switch(config)# show ospfv3 100
 (Optional)

Displays the OSPFv3 authentication configuration at the process level.

Step 8

(Optional) show ospfv3 interface interface-type slot/port

Example:

switch(config)# show ospfv3 interface
ethernet 1/1
 (Optional)

Displays the OSPFv3 authentication configuration at the interface level.

Step 9

(Optional) copy running-config startup-config

Example:

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

Saves this configuration change.

Configuring Advanced OSPFv3

Configure OSPFv3 after you have designed your OSPFv3 network.

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 Configuring Route Policy Manager.

You must enable OSPFv3 (see the Enabling OSPFv3 section).

Procedure

  Command or Action Purpose

Step 1

configure terminal

Example:

switch# configure terminal
switch(config)#

Enters global 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

(Optional) 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

(Optional) copy running-config startup-config

Example:

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

Saves this configuration change.

Example

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.

Procedure

  Command or Action Purpose

Step 1

configure terminal

Example:

switch# configure terminal
switch(config)#

Enters global 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

(Optional) 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

(Optional) 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

(Optional) copy running-config startup-config

Example:

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

Saves this configuration change.

Example

This example 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:

Procedure

Command or Action 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. 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.

Procedure

  Command or Action Purpose

Step 1

configure terminal

Example:

switch# configure terminal
switch(config)#

Enters global 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

(Optional) 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

(Optional) 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

Saves this configuration change.

Example

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 have configured a primary area for the interface (see the Configuring Networks in OSPFv3 section).

Procedure

  Command or Action Purpose

Step 1

configure terminal

Example:

switch# configure terminal
switch(config)#

Enters global 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.

Note

 

Beginning with Cisco NX-OS Release 7.0(3)I5(1), the instance tag argument is optional. If you do not specify an instance the multi-area configuration is applied to the same instance that is configured for the primary area on tha interface.

Step 4

(Optional) 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

(Optional) copy running-config startup-config

Example:

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

Saves this configuration change.

Example

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).

Procedure

  Command or Action Purpose

Step 1

configure terminal

Example:

switch# configure terminal
switch(config)#

Enters global 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

(Optional) show ipv6 ospfv3 virtual-link [ brief ]

Example:

switch(config-if)# show ipv6 ospfv3 virtual-link
 (Optional)

Displays OSPFv3 virtual link information.

Step 5

(Optional) copy running-config startup-config

Example:

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

Saves this configuration change.

Example

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

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

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

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

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).

Procedure

  Command or Action Purpose

Step 1

configure terminal

Example:

switch# configure terminal
switch(config)#

Enters global 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.

Note

 

This command ignores match 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

Saves this configuration change.

Example

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-confi

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).

Procedure

  Command or Action Purpose

Step 1

configure terminal

Example:

switch# configure terminal
switch(config)#

Enters global 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. Thenum-retries range is from 1 to 12. The timeout range is from 60 to 600 seconds. The default is 300 seconds.

Step 6

(Optional) show running-config ospfv3

Example:

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

Displays the OSPFv3 configuration.

Step 7

(Optional) copy running-config startup-config

Example:

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

Saves this configuration change.

Example

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).

Procedure

  Command or Action Purpose

Step 1

configure terminal

Example:

switch# configure terminal
switch(config)#

Enters global 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 addressesand o ptionally 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

(Optional) show ipv6 ospfv3 summary-address

Example:

switch(config-router)# show ipv6 ospfv3 summary-addres
 (Optional)

Displays information about OSPFv3 summary addresses

Step 7

(Optional) copy running-config startup-config

Example:

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

Saves this configuration change.

Example

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.

Procedure

  Command or Action Purpose

Step 1

configure terminal

Example:

switch# configure terminal
switch(config)#

Enters global 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

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 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

(Optional) copy running-config startup-config

Example:

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

Saves this configuration change.

Example

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.

Procedure

  Command or Action Purpose

Step 1

configure terminal

Example:

switch# configure terminal
switch(config)#

Enters global 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

(Optional) show ipv6 ospfv3 instance-tag

Example:

switch(config-if)# show ipv6 ospfv3 201
 (Optional)

Displays OSPFv3 information.

Step 8

(Optional) copy running-config startup-config

Example:

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

Saves this configuration change.

Example

This example 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:

Procedure

Command or Action 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).

Procedure

  Command or Action 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 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

(Optional) 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 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 RemoteOfficeVR

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

(Optional) copy running-config startup-config

Example:

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

Saves this configuration change.

Example

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

To display the OSPFv3 configuration, perform one of the following tasks:

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 ospfv3 process

Displays the OSPFv3 authentication configuration at the process level.

show ospfv3 interface interface-type slot/port

Displays the OSPFv3 authentication configuration at the interface level.

show running-configuration ospfv3

Displays the current running OSPFv3 configuration.

Monitoring OSPFv3

To display OSPFv3 statistics, use the following commands:

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

This example shows how to configure OSPFv3:
feature ospfv3
router ospfv3 201
router-id 290.0.2.1
 
interface ethernet 1/2
ipv6 address 2001:0DB8::1/48

ipv6 ospfv3 201 area 0.0.0.10

Additional References

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

MIBs

MIBs

MIBs Link

  • OSPF-MIB

  • OSPF-TRAP-MIB

 To locate and download MIBs, go to the following: MIB Locator.