Chapter 1. Configuring IP Unicast Routing

- Information About IP Unicast Routing

- How to Enable IP Unicast Routing

- Monitoring and Maintaining the IP Network

- Configuration Examples for IP Unicast Routing

- Additional References

- Feature Information for IP Unicast Routing

Information About IP Unicast Routing

This module describes how to configure IPv4 unicast routing on a device.

Note

In addition to IPv4 traffic, you can also enable IPv6 unicast routing and configure interfaces to forward IPv6 traffic

- IP Routing Overview

- Types of Routing

- Static Unicast Routes

- Default Routes and Networks

- Routing Information Protocol

- Default RIP Configuration

IP Routing Overview

In some network environments, VLANs are associated with individual networks or subnetworks. In an IP network, each subnetwork is mapped to an individual VLAN. Configuring VLANs helps control the size of the broadcast domain and keeps local traffic local. However, network devices in different VLANs cannot communicate with one another without a Layer 3 device (router) to route traffic between the VLAN, referred to as inter-VLAN routing. You configure one or more routers to route traffic to the appropriate destination VLAN.

Routing Topology Example

When Host A in VLAN 10 needs to communicate with Host B in VLAN 10, it sends a packet addressed to that host. Switch A forwards the packet directly to Host B, without sending it to the router.

When Host A sends a packet to Host C in VLAN 20, Switch A forwards the packet to the router, which receives the traffic on the VLAN 10 interface. The router checks the routing table, finds the correct outgoing interface, and forwards the packet on the VLAN 20 interface to Switch B. Switch B receives the packet and forwards it to Host C.

Types of Routing

Routers and Layer 3 switches can route packets in these ways:

- By using default routing

- By using preprogrammed static routes for the traffic

The switch supports static routes and default routes. It supports RIP for both IPv4 and IPv6 versions.

Static Unicast Routes

Static unicast routes are user-defined routes that cause packets moving between a source and a destination to take a specified path. Static routes can be important if the router cannot build a route to a particular destination and are useful for specifying a gateway of last resort to which all unroutable packets are sent.

The switch retains static routes until you remove them. However, you can override static routes with dynamic routing information by assigning administrative distance values. Each dynamic routing protocol has a default administrative distance, as listed in the following table. If you want a static route to be overridden by information from a dynamic routing protocol, set the administrative distance of the static route higher than that of the dynamic protocol.

Dynamic Routing Protocol Default Administrative Distances

Route Source

Default Distance

Connected interface

0

Static route

1

Enhanced IRGP summary route

5

RIP

120

Unknown

225

Static routes that point to an interface are advertised through RIP and other dynamic routing protocols, whether or not static redistribute router configuration commands were specified for those routing protocols. These static routes are advertised because static routes that point to an interface are considered in the routing table to be connected and hence lose their static nature. However, if you define a static route to an interface that is not one of the networks defined in a network command, no dynamic routing protocols advertise the route unless a redistribute static command is specified for these protocols.

When an interface goes down, all static routes through that interface are removed from the IP routing table. When the software can no longer find a valid next hop for the address specified as the forwarding router's address in a static route, the static route is also removed from the IP routing table.

Default Routes and Networks

A router might not be able to learn the routes to all other networks. To provide complete routing capability, you can use some routers as smart routers and give the remaining routers default routes to the smart router. (Smart routers have routing table information for the entire internetwork.) These default routes can be dynamically learned or can be configured in the individual routers. Most dynamic interior routing protocols include a mechanism for causing a smart router to generate dynamic default information that is then forwarded to other routers.

If a router has a directly connected interface to the specified default network, the dynamic routing protocols running on that device generate a default route. In RIP, it advertises the pseudonetwork 0.0.0.0.

A router that is generating the default for a network also might need a default of its own. One way a router can generate its own default is to specify a static route to the network 0.0.0.0 through the appropriate device.

When default information is passed through a dynamic routing protocol, no further configuration is required. The system periodically scans its routing table to choose the optimal default network as its default route. In Interior Gateway Routing Protocol (IGRP) networks, there might be several candidate networks for the system default. Cisco routers use administrative distance and metric information to set the default route or the gateway of last resort.

If dynamic default information is not being passed to the system, candidates for the default route are specified with the ip default-network global configuration command. If this network appears in the routing table from any source, it is flagged as a possible choice for the default route. If the router has no interface on the default network, but does have a path to it, the network is considered as a possible candidate, and the gateway to the best default path becomes the gateway of last resort.

Routing Information Protocol

The Routing Information Protocol (RIP) is an Interior Gateway Protocol (IGP) created for use in small, homogeneous networks. It is a distance-vector routing protocol that uses broadcast UDP data packets to exchange routing information. The protocol is documented in RFC 1058. You can find detailed information about RIP in IP Routing Fundamentals, published by Cisco Press.

Using RIP, a device sends routing information updates (advertisements) every 30 seconds. If a router does not receive an update from another router for 180 seconds or more, it marks the routes served by that router as unusable. If there is still no update after 240 seconds, the router removes all routing table entries for the non-updating router.

RIP uses hop counts to rate the value of different routes. The hop count is the number of routers that can be traversed in a route. A directly connected network has a hop count of zero; a network with a hop count of 16 is unreachable. This small range (0 to 15) makes RIP unsuitable for large networks.

If the router has a default network path, RIP advertises a route that links the router to the pseudonetwork 0.0.0.0. The 0.0.0.0 network does not exist; it is treated by RIP as a network to implement the default routing feature. The device advertises the default network if a default was learned by RIP or if the router has a gateway of last resort and RIP is configured with a default metric. RIP sends updates to the interfaces in specified networks. If an interface’s network is not specified, it is not advertised in any RIP update.

Default RIP Configuration

Default RIP Configuration

Feature

Default Setting

Auto summary

Enabled.

Default-information originate

Disabled.

Default metric

Built-in; automatic metric translations.

IP RIP authentication key-chain

No authentication.

Authentication mode: clear text.

IP RIP triggered

Disabled

IP split horizon

Varies with media.

Neighbor

None defined.

Network

None specified.

Offset list

Disabled.

Output delay

0 milliseconds.

Timers basic

- Update: 30 seconds.

- Invalid: 180 seconds.

- Hold-down: 180 seconds.

- Flush: 240 seconds.

Validate-update-source

Enabled.

Version

Receives RIP Version 1 and 2 packets; sends Version 1 packets.

How to Enable IP Unicast Routing

By default, IP routing is disabled on a device.

In these procedures, the specified interface can be a switch virtual interface (SVI)-a VLAN interface or a physical port interface created by using the interface vlan vlan_id or interface type number commands respectively, and by default a Layer 3 interface. All Layer 3 interfaces on which routing will occur must have IP addresses assigned to them.

Note

The device supports 16 static routes (including user-configured routes and the default route) and any directly connected routes and default routes for the management interface.

Procedures for configuring routing:

- To support VLAN interfaces, create and configure VLANs on the device, and assign VLAN membership to Layer 2 interfaces.

- Configure Layer 3 interfaces.

- Enable IP routing on the device.

- Assign IP addresses to the Layer 3 interfaces.

- Configure static routes.

- Enabling IP Unicast Routing

- Assigning IP Addresses to SVIs

- Configuring Default Routes and Networks

- Configuring Basic RIP Parameters

- Configuring RIP Authentication

Enabling IP Unicast Routing

By default, the device is in Layer 2 switching mode and IP routing is disabled. To use the Layer 3 capabilities of the device, you must enable IP routing.

Procedure

Step 1

enable

Example:

Device> enable

Enables privileged EXEC mode.

- Enter your password if prompted.

Step 2

configure terminal

Example:

Device# configure terminal

Enters global configuration mode.

Step 3

ip routing

Example:

Device(config)# ip routing

Enables IP routing.

Step 4

end

Example:

Device(config)# end

Exits global configuration mode and returns to privileged EXEC mode.

Assigning IP Addresses to SVIs

To configure IP routing, you need to assign IP addresses to Layer 3 network interfaces. This enables communication with the hosts of those interfaces that use IP. IP routing is disabled by default, and no IP addresses are assigned to SVIs.

An IP address identifies a location to which IP packets can be sent. Some IP addresses are reserved for special uses and cannot be used for host, subnet, or network addresses. RFC 1166, “Internet Numbers,” contains the official description of IP addresses.

An interface can have one primary IP 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 referred to as a subnet mask. To receive an assigned network number, contact your Internet service provider.

Follow these steps to assign an IP address and a network mask to an SVI:

Procedure

Step 1

enable

Example:

Device> enable

Enables privileged EXEC mode.

- Enter your password if prompted.

Step 2

configure terminal

Example:

Device# configure terminal

Enters global configuration mode.

Step 3

interface vlan vlan-id

Example:

Device(config)# interface vlan 1

Enters interface configuration mode, and specifies the Layer 3 VLAN to configure.

Step 4

ip address ip-address subnet-mask

Example:

Device(config-if)# ip address 10.1.5.1 255.255.255.0

Configures the IP address and IP subnet mask.

Step 5

end

Example:

Device(config-if)# end

Exits interface configuration mode and returns to privileged EXEC mode.

Step 6

show interfaces vlan [vlan-id]

Example:

Device# show interfaces vlan 4

Displays statistics for all VLAN interfaces configured on the device.

Configuring Default Routes and Networks

Procedure

Step 1

enable

Example:

Device> enable

Enables privileged EXEC mode.

- Enter your password if prompted.

Step 2

configure terminal

Example:

Device# configure terminal

Enters global configuration mode.

Step 3

ip route network number

Example:

(config)# ip route 0.0.0.0 0.0.0.0 10.10.10.2

Specifies a default network.

Step 4

end

Example:

Device(config)# end

Exits global configuration mode and returns to privileged EXEC mode.

Step 5

show ip route

Example:

Device# show ip route

Displays the selected default route in the gateway of last resort display.

Configuring Basic RIP Parameters

To configure RIP, you enable RIP routing for a network and optionally configure other parameters. On the device, RIP configuration commands are ignored until you configure the network number.

Procedure

Step 1

enable

Example:

Device> enable

Enables privileged EXEC mode.

- Enter your password if prompted.

Step 2

configure terminal

Example:

Device# configure terminal

Enters global configuration mode.

Step 3

ip routing

Example:

Device(config)# ip routing

Enables IP routing. (Required only if IP routing is disabled.)

Step 4

router rip

Example:

Device(config)# router rip

Enables a RIP routing process, and enters router configuration mode.

Step 5

network network number

Example:

Device(config-router)# network 10.0.0.0

Associates a network with a RIP routing process. You can specify multiple network commands. RIP routing updates are sent and received through interfaces only on these networks.

Note

You must configure a network number for the RIP commands to take effect.

Step 6

neighbor ip-address

Example:

Device(config-router)# neighbor 10.2.5.1

(Optional) Defines a neighboring router with which to exchange routing information. This step allows routing updates from RIP (normally a broadcast protocol) to reach nonbroadcast networks.

Step 7

offset-list [access-list number | name] {in | out} offset [type number]

Example:

Device(config-router)# offset-list 103 in 10

(Optional) Applies an offset list to routing metrics to increase incoming and outgoing metrics to routes learned through RIP. You can limit the offset list with an access list or an interface.

Step 8

timers basic update invalid holddown flush

Example:

Device(config-router)# timers basic 45 360 400 300

(Optional) Adjusts routing protocol timers. Valid ranges for all timers are 0 to 4294967295 seconds.

- update : The time between sending routing updates. The default is 30 seconds.

- invalid : The timer after which a route is declared invalid. The default is 180 seconds.

- holddown : The time before a route is removed from the routing table. The default is 180 seconds.

- flush : The amount of time for which routing updates are postponed. The default is 240 seconds.

Step 9

version {1 | 2}

Example:

Device(config-router)# version 2

(Optional) Configures the switch to receive and send only RIP Version 1 or RIP Version 2 packets. By default, the switch receives Version 1 and 2 but sends only Version 1.
You can also use the interface commands ip rip {send | receive} version 1 | 2 | 1 2} to control what versions are used for sending and receiving on interfaces.

Step 10

no auto summary

Example:

Device(config-router)# no auto summary

(Optional) Disables automatic summarization. By default, the switch summarizes subprefixes when crossing classful network boundaries. Disable summarization (RIP Version 2 only) to advertise subnet and host routing information to classful network boundaries.

Step 11

end

Example:

Device(config-router)# end

Exits router configuration mode and returns to privileged EXEC mode.

Step 12

show ip protocols

Example:

Device# show ip protocols

Displays the parameters and the current state of the active routing protocol process.

Configuring RIP Authentication

RIP Version 1 does not support authentication. If you are sending and receiving RIP Version 2 packets, you can enable RIP authentication on an interface. The key chain specifies the set of keys that can be used on the interface. If a key chain is not configured, no authentication is performed, not even the default.

The device supports two modes of authentication on interfaces for which RIP authentication is enabled: plain text and MD5. The default is plain text.

Procedure

Step 1

enable

Example:

Device> enable

Enables privileged EXEC mode.

- Enter your password if prompted.

Step 2

configure terminal

Example:

Device# configure terminal

Enters global configuration mode.

Step 3

interface interface-id

Example:

Device(config)# interface gigabitethernet 1/0/1

Or
Device(config)# interface fastethernet 1/0/1

Configures the interface and enters interface configuration mode.

Step 4

ip rip authentication key-chain name-of-chain

Example:

Device(config-if)# ip rip authentication key-chain trees

Enables RIP authentication.

Step 5

ip rip authentication mode {text | md5}

Example:

Device(config-if)# ip rip authentication mode md5

Configures the interface to use plain text authentication (the default) or MD5 digest authentication.

Step 6

end

Example:

Device(config-if)# end

Exits interface configuration mode and returns to privileged EXEC mode.

Monitoring and Maintaining the IP Network

Use the following commands to display specific statistics.

Commands to Clear IP Routes or Display Route Status

Command

Purpose

show ip route [address [mask] [longer-prefixes]]

Displays the current state of the routing table.

show ip route summary

Displays the current state of the routing table in summary form.

Configuration Examples for IP Unicast Routing

- Example: Enabling IP Unicast Routing

- Example: Assigning IP Addresses to SVIs

- Example: Displaying Current Status of the Routing Table

Example: Enabling IP Unicast Routing

This example shows how to enable IP unicast routing.

Device> enable
Device# configure terminal
Device(config)# ip routing
Device(config)# end

Example: Assigning IP Addresses to SVIs

This example shows how to assign an IP address and a network mask to an SVI.

Device> enable
Device# configure terminal
Device(config)# interface vlan 4
Device(config-if)# ip address 10.1.5.1 255.255.255.0
Device(config-if)# exit
Device# show interfaces vlan 4

Example: Displaying Current Status of the Routing Table

This following is sample output from the show ip route command:

Device# show ip route

Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP
a - application route
+ - replicated route, % - next hop override, p - overrides from PfR

Gateway of last resort is 192.0.2.5 to network 0.0.0.0

S* 0.0.0.0/0 [0/0] via 192.0.2.5
10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C 10.3.3.0/24 is directly connected, GigabitEthernet1/0/23
L 10.3.3.2/32 is directly connected, GigabitEthernet1/0/23
172.16.0.0/24 is subnetted, 1 subnets
S 172.16.0.1 [1/0] via 192.0.2.5
10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C 192.0.2.4/24 is directly connected, Vlan1
L 192.0.2.10/24 is directly connected, Vlan1
209.165.201.0/24 is subnetted, 1 subnets
S 209.165.201.1 [1/0] via 192.0.2.5
Device#

S -- Stand for static route.

Additional References

Related Documents

Related Topic

Document Title

For complete syntax and usage information for the commands used in this chapter.

Consolidated Platform Command Reference, Cisco IOS Release 15.2(7)Ex (Catalyst 1000 Switches)

Technical Assistance

Description

Link

The Cisco Support website provides extensive online resources, including documentation and tools for troubleshooting and resolving technical issues with Cisco products and technologies.

To receive security and technical information about your products, you can subscribe to various services, such as the Product Alert Tool (accessed from Field Notices), the Cisco Technical Services Newsletter, and Really Simple Syndication (RSS) Feeds.

Access to most tools on the Cisco Support website requires a Cisco.com user ID and password.

http://www.cisco.com/support

Feature Information for IP Unicast Routing

The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

Use the Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.

Feature Information for IP Unicast Routing

Feature Name

Releases

Feature Information

IP Unicast Routing

Cisco IOS Release 15.2(7)E1

This feature was introduced.

Chapter 2. Configuring IPv6 Unicast Routing

- Information About IPv6 Unicast Routing

- How to Configure IPv6 Unicast Routing

- Monitoring IPv6 Unicast Routing

- Configuration Examples for IPv6 Unicast Routing

- Feature History and Information for IPv6 Unicast Routing

Information About IPv6 Unicast Routing

This chapter describes how to configure IPv6 host functions on the .

For information about configuring IPv6 Multicast Listener Discovery (MLD) snooping, see Configuring MLD Snooping.

- Understanding IPv6

- Default IPv6 Configuration

Understanding IPv6

IPv4 users can move to IPv6 and receive services such as end-to-end security, quality of service (QoS), and globally unique addresses. The IPv6 address space reduces the need for private addresses and Network Address Translation (NAT) processing by border routers at network edges.

For information about how Cisco Systems implements IPv6, go to: http://www.cisco.com/en/US/products/ps6553/products_ios_technology_home.html

- IPv6 Addresses

- Supported IPv6 Unicast Routing Features

IPv6 Addresses

The switch supports only IPv6 unicast addresses. It does not support site-local unicast addresses, or anycast addresses.

The IPv6 128-bit addresses are represented as a series of eight 16-bit hexadecimal fields separated by colons in the format: n:n:n:n:n:n:n:n. This is an example of an IPv6 address:

2031:0000:130F:0000:0000:09C0:080F:130B

For easier implementation, leading zeros in each field are optional. This is the same address without leading zeros:

2031:0:130F:0:0:9C0:80F:130B

You can also use two colons (::) to represent successive hexadecimal fields of zeros, but you can use this short version only once in each address:

2031:0:130F::09C0:080F:130B

For more information about IPv6 address formats, address types, and the IPv6 packet header, see the http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipv6_basic/configuration/xe-3e/ip6b-xe-3e-book.html of Cisco IOS IPv6 Configuration Library on Cisco.com.

Supported IPv6 Unicast Routing Features

The following sections describe the IPv6 protocol features supported by the switch:

- 128-Bit Wide Unicast Addresses

- DNS for IPv6

- ICMPv6

- Neighbor Discovery

- IPv6 Stateless Autoconfiguration and Duplicate Address Detection

- IPv6 Applications

- Static Routes for IPv6

- RIP for IPv6

- SNMP and Syslog Over IPv6

- HTTP(S) Over IPv6

128-Bit Wide Unicast Addresses

The switch supports aggregatable global unicast addresses and link-local unicast addresses. It does not support site-local unicast addresses.

- Aggregatable global unicast addresses are IPv6 addresses from the aggregatable global unicast prefix. The address structure enables strict aggregation of routing prefixes and limits the number of routing table entries in the global routing table. These addresses are used on links that are aggregated through organizations and eventually to the Internet service provider.

These addresses are defined by a global routing prefix, a subnet ID, and an interface ID. Current global unicast address allocation uses the range of addresses that start with binary value 001 (2000::/3). Addresses with a prefix of 2000::/3(001) through E000::/3(111) must have 64-bit interface identifiers in the extended unique identifier (EUI)-64 format.

- Link local unicast addresses can be automatically configured on any interface by using the link-local prefix FE80::/10(1111 1110 10) and the interface identifier in the modified EUI format. Link-local addresses are used in the neighbor discovery protocol (NDP) and the stateless autoconfiguration process. Nodes on a local link use link-local addresses and do not require globally unique addresses to communicate. IPv6 routers do not forward packets with link-local source or destination addresses to other links.

DNS for IPv6

IPv6 supports Domain Name System (DNS) record types in the DNS name-to-address and address-to-name lookup processes. The DNS AAAA resource record types support IPv6 addresses and are equivalent to an A address record in IPv4. The switch supports DNS resolution for IPv4 and IPv6.

ICMPv6

The Internet Control Message Protocol (ICMP) in IPv6 generates error messages, such as ICMP destination unreachable messages, to report errors during processing and other diagnostic functions. In IPv6, ICMP packets are also used in the neighbor discovery protocol and path MTU discovery.

Neighbor Discovery

The switch supports Neighbor Discovery Protocol (NDP) for IPv6, a protocol running on top of ICMPv6, and static neighbor entries for IPv6 stations that do not support NDP. The IPv6 neighbor discovery process uses ICMP messages and solicited-node multicast addresses to determine the link-layer address of a neighbor on the same network (local link), to verify the reachability of the neighbor, and to keep track of neighboring routers.

The switch supports ICMPv6 redirect for routes with mask lengths less than 64 bits. ICMP redirect is not supported for host routes or for summarized routes with mask lengths greater than 64 bits.

Neighbor discovery throttling ensures that the switch CPU is not unnecessarily burdened while it is in the process of obtaining the next hop forwarding information to route an IPv6 packet. The switch drops any additional IPv6 packets whose next hop is the same neighbor that the switch is actively trying to resolve. This drop avoids further load on the CPU.

Note

IPv6 next hop security features are not supported in .

IPv6 Stateless Autoconfiguration and Duplicate Address Detection

The switch uses stateless autoconfiguration to manage link, subnet, and site addressing changes, such as management of host and mobile IP addresses. A host autonomously configures its own link-local address, and booting nodes send router solicitations to request router advertisements for configuring interfaces.

IPv6 Applications

The switch has IPv6 support for these applications:

- Ping, traceroute, Telnet

- Secure Shell (SSH) over an IPv6 transport

- HTTP server access over IPv6 transport

- DNS resolver for AAAA over IPv4 transport

- Cisco Discovery Protocol (CDP) support for IPv6 addresses

Static Routes for IPv6

Static routes are manually configured and define an explicit route between two networking devices. Static routes are useful for smaller networks with only one path to an outside network or to provide security for certain types of traffic in a larger network.

RIP for IPv6

Routing Information Protocol (RIP) for IPv6 is a distance-vector protocol that uses hop count as a routing metric. It includes support for IPv6 addresses and prefixes and the all-RIP-routers multicast group address FF02::9 as the destination address for RIP update messages.

SNMP and Syslog Over IPv6

To support both IPv4 and IPv6, IPv6 network management requires both IPv6 and IPv4 transports. Syslog over IPv6 supports address data types for these transports.

Simple Network Management Protocol (SNMP) and syslog over IPv6 provide these features:

- Support for both IPv4 and IPv6

- IPv6 transport for SNMP and to modify the SNMP agent to support traps for an IPv6 host

- SNMP- and syslog-related MIBs to support IPv6 addressing

- Configuration of IPv6 hosts as trap receivers

For support over IPv6, SNMP modifies the existing IP transport mapping to simultaneously support IPv4 and IPv6. These SNMP actions support IPv6 transport management:

- Opens User Datagram Protocol (UDP) SNMP socket with default settings

- Provides a new transport mechanism called SR_IPV6_TRANSPORT

- Sends SNMP notifications over IPv6 transport

- Supports SNMP-named access lists for IPv6 transport

- Supports SNMP proxy forwarding using IPv6 transport

- Verifies SNMP Manager feature works with IPv6 transport

HTTP(S) Over IPv6

The HTTP client sends requests to both IPv4 and IPv6 HTTP servers, which respond to requests from both IPv4 and IPv6 HTTP clients. URLs with literal IPv6 addresses must be specified in hexadecimal using 16-bit values between colons.

The accept socket call chooses an IPv4 or IPv6 address family. The accept socket is either an IPv4 or IPv6 socket. The listening socket continues to listen for both IPv4 and IPv6 signals that indicate a connection. The IPv6 listening socket is bound to an IPv6 wildcard address.

The underlying TCP/IP stack supports a dual-stack environment. HTTP relies on the TCP/IP stack and the sockets for processing network-layer interactions.

Basic network connectivity (ping ) must exist between the client and the server hosts before HTTP connections can be made.

Default IPv6 Configuration

Default IPv6 Configuration

Feature

Default Setting

IPv6 addresses

None configured

How to Configure IPv6 Unicast Routing

- Configuring IPv6 Addressing and Enabling IPv6 Routing

- Configuring IPv6 ICMP Rate Limiting

- Configuring Static Routing for IPv6 (CLI)

- Configuring RIP for IPv6

Configuring IPv6 Addressing and Enabling IPv6 Routing

This section describes how to assign IPv6 addresses to individual Layer 3 interfaces and to globally forward IPv6 traffic on the switch.

Before configuring IPv6 on the switch, note the following:

In the ipv6 address interface configuration command, you must enter the ipv6-address and ipv6-prefix variables with the address specified in hexadecimal using 16-bit values between colons. The prefix-length variable (preceded by a slash [/]) is a decimal value that shows how many of the high-order contiguous bits of the address comprise the prefix (the network portion of the address).

To forward IPv6 traffic on an interface, you must configure a global IPv6 address on that interface. Configuring an IPv6 address on an interface automatically configures a link-local address and activates IPv6 for the interface. The configured interface automatically joins these required multicast groups for that link:

- solicited-node multicast group FF02:0:0:0:0:1:ff00::/104 for each unicast address assigned to the interface (this address is used in the neighbor discovery process.)

- all-nodes link-local multicast group FF02::1

- all-routers link-local multicast group FF02::2

Beginning in privileged EXEC mode, follow these steps to assign an IPv6 address to a Layer 3 interface and enable IPv6 forwarding:

Procedure

Step 1

configure terminal

Example:

Device# configure terminal

Enters global configuration mode.

Step 2

interface interface-id

Example:

Device(config)# interface gigabitethernet 1/0/1

Or
Device(config)# interface fastethernet 1/0/1

Enters interface configuration mode, and specifies the Layer 3 interface to configure.

Step 3

Use one of the following:

- ipv6 address ipv6-prefix/prefix length eui-64

- ipv6 address ipv6-address/prefix length

- ipv6 address ipv6-address link-local

- ipv6 enable

Example:

Device(config-if)# ipv6 address 2001:0DB8:c18:1::/64 eui 64

Device(config-if)# ipv6 address 2001:0DB8:c18:1::/64

Device(config-if)# ipv6 address FE80::/10 link-local

Device(config-if)# ipv6 enable

- ipv6 address ipv6-prefix/prefix length eui-64 : Specifies a global IPv6 address with an extended unique identifier (EUI) in the low-order 64 bits of the IPv6 address. Specify only the network prefix; the last 64 bits are automatically computed from the switch MAC address. This enables IPv6 processing on the interface.

- ipv6 address ipv6-address/prefix length : Manually configures an IPv6 address on the interface.

- ipv6 address ipv6-address link-local : Specifies a link-local address to be used on the interface instead of the link-local address that is automatically configured when IPv6 is enabled on the interface. This command enables IPv6 processing on the interface.

- ipv6 enable : Automatically configures an IPv6 link-local address on the interface, and enables the interface for IPv6 processing. The link-local address can only be used to communicate with nodes on the same link.

Step 4

end

Example:

Device(config-if)#end

Returns to privileged EXEC mode.

Step 5

show ipv6 interface interface-id

Example:

Device# show ipv6 interface gigabitethernet 1/0/1

Or
Device# show ipv6 interface fastethernet 1/0/1

Verifies your entries.

Step 6

copy running-config startup-config

Example:

Device# copy running-config startup-config

(Optional) Saves your entries in the configuration file.

Configuring IPv6 ICMP Rate Limiting

ICMP rate limiting is enabled by default with a default interval between error messages of 100 milliseconds and a bucket size (maximum number of tokens to be stored in a bucket) of 10.

Beginning in privileged EXEC mode, follow these steps to change the ICMP rate-limiting parameters:

Procedure

Step 1

configure terminal

Example:

Device# configure terminal

Enters global configuration mode.

Step 2

ipv6 icmp error-interval interval [bucketsize]

Example:

Device(config)# ipv6 icmp error-interval 50 20

Configures the interval and bucket size for IPv6 ICMP error messages:

- interval —The interval (in milliseconds) between tokens being added to the bucket. The range is from 0 to 2147483647 milliseconds.

- bucketsize —(Optional) The maximum number of tokens stored in the bucket. The range is from 1 to 200.

Step 3

end

Example:

Device(config)# end

Returns to privileged EXEC mode.

Step 4

show ipv6 interface [interface-id]

Example:

Device# show ipv6 interface gigabitethernet 1/0/1

Or
Device# show ipv6 interface fastethernet 1/0/1

Verifies your entries.

Step 5

copy running-config startup-config

Example:

Device# copy running-config startup-config

(Optional) Saves your entries in the configuration file.

Configuring Static Routing for IPv6 (CLI)

Beginning in privileged EXEC mode, follow these steps to configure a static IPv6 route:

Note

The switch supports 16 IPv6 static routes.

Before you begin

Before configuring a static IPv6 route, you must:

- Enable routing by using the ip routing global configuration command.

- Enable the forwarding of IPv6 packets by using the ipv6 unicast-routing global configuration command.

- Enable IPv6 on at least one Layer 3 interface by configuring an IPv6 address on the interface.

Procedure

Step 1

configure terminal

Example:

Device# configure terminal

Enters global configuration mode.

Step 2

ipv6 route ipv6-prefix/prefix length {ipv6-address | interface-id [ipv6-address]} [administrative distance]

Example:

Device(config)# ipv6 route 2001:0DB8::/32 gigabitethernet 1/0/1 130

Or
Device(config)# ipv6 route 2001:0DB8::/32 fastethernet 0/1 130

Configures a static IPv6 route. You must configure one of the following options:

- ipv6-prefix : The IPv6 network that is the destination of the static route. It can also be a hostname when static host routes are configured.

- /prefix length: The length of the IPv6 prefix. A decimal value that shows how many of the high-order contiguous bits of the address comprise the prefix (the network portion of the address). A slash mark must precede the decimal value.

- ipv6-address : The IPv6 address of the next hop that can be used to reach the specified network. The IPv6 address of the next hop need not be directly connected; recursion is done to find the IPv6 address of the directly connected next hop. The address must be in the form documented in RFC 2373, specified in hexadecimal using 16-bit values between colons.

- interface-id : Specifies direct static routes from point-to-point and broadcast interfaces. With point-to-point interfaces, there is no need to specify the IPv6 address of the next hop. With broadcast interfaces, you should always specify the IPv6 address of the next hop, or ensure that the specified prefix is assigned to the link, specifying a link-local address as the next hop. You can optionally specify the IPv6 address of the next hop to which packets are sent.

Note

You must specify an interface-id when using a link-local address as the next hop (the link-local next hop must also be an adjacent router).

- administrative distance —(Optional) An administrative distance. The range is 1 to 254; the default value is 1, which gives static routes precedence over any other type of route except connected routes. To configure a floating static route, use an administrative distance greater than that of the dynamic routing protocol.

Step 3

end

Example:

Device(config)# end

Returns to privileged EXEC mode.

Step 4

Use one of the following:

- show ipv6 static [ ipv6-address | ipv6-prefix/prefix length ] [interface interface-id ] [detail]][recursive] [detail]

- show ipv6 route static

Example:

Device# show ipv6 static 2001:0DB8::/32 interface gigabitethernet 1/0/1

or

Device# show ipv6 route static

Verifies your entries by displaying the contents of the IPv6 routing table.

- interface interface-id (Optional): Displays only those static routes with the specified interface as an egress interface.

- recursive (Optional): Displays only recursive static routes. The recursive keyword is mutually exclusive with the interface keyword, but it can be used with or without the IPv6 prefix included in the command syntax.

- detail (Optional): Displays this additional information:

- For valid recursive routes, the output path set, and maximum resolution depth.

- For invalid routes, the reason why the route is not valid.

Step 5

copy running-config startup-config

Example:

Device# copy running-config startup-config

(Optional) Saves your entries in the configuration file.

Configuring RIP for IPv6

Beginning in privileged EXEC mode, follow these steps to configure RIP routing for IPv6:

Before you begin

Before configuring the switch to run IPv6 RIP, you must:

- Enable routing by using the ip routing global configuration command.

- Enable the forwarding of IPv6 packets by using the ipv6 unicast-routing global configuration command.

- Enable IPv6 on at least one Layer 3 interface by configuring an IPv6 address on the interface.

Procedure

Step 1

configure terminal

Example:

Device# configure terminal

Enters global configuration mode.

Step 2

ipv6 router rip name

Example:

Device(config)# ipv6 router rip cisco

Configures an IPv6 RIP routing process, and enters router configuration mode for the process.

Step 3

maximum-paths number-paths

Example:

Device(config-router)# maximum-paths 6

(Optional) Defines the maximum number of equal-cost routes that IPv6 RIP can support. The range is from 1 to 8, and the default is 8 routes.

Step 4

exit

Example:

Device(config-router)# exit

Returns to global configuration mode.

Step 5

interface interface-id

Example:

Device(config)# interface gigabitethernet 1/0/1

Or
Device(config)# interface fastethernet 1/0/1

Enters interface configuration mode, and specifies the Layer 3 interface to configure.

Step 6

ipv6 rip name enable

Example:

Device(config-if)# ipv6 rip cisco enable

Enables the specified IPv6 RIP routing process on the interface.

Step 7

ipv6 rip name default-information {only | originate}

Example:

Device(config-if)# ipv6 rip cisco default-information only

(Optional) Originates the IPv6 default route (::/0) into the RIP routing process updates sent from the specified interface.

Note

To avoid routing loops after the IPv6 default route (::/0) is originated from any interface, the routing process ignores all default routes received on any interface.

- only : Select to originate the default route, but suppress all other routes in the updates sent on this interface.

- originate : Select to originate the default route in addition to all other routes in the updates sent on this interface.

Step 8

end

Example:

Device(config)# end

Returns to privileged EXEC mode.

Step 9

Use one of the following:

- show ipv6 rip [name] [ interface interface-id] [ database ] [ next-hops ]

- show ipv6 rip

Example:

Device# show ipv6 rip cisco interface gigabitethernet 1/0/1

or

Device# show ipv6 rip

- The show ipv6 rip cisco interface command displays information about current IPv6 RIP processes.

- The show ipv6 rip command displays the current contents of the IPv6 routing table.

Step 10

copy running-config startup-config

Example:

Device# copy running-config startup-config

(Optional) Saves your entries in the configuration file.

Monitoring IPv6 Unicast Routing

- Displaying IPv6

Displaying IPv6

The following table lists the commands you can use to monitor IPv6 unicast routing features. For complete syntax and usage information for these commands, see the command reference document.

Command

Purpose

show ipv6 access-list

Displays a summary of access lists.

show ipv6 cef

Displays Cisco Express Forwarding for IPv6.

show ipv6 interface interface-id

Displays IPv6 interface status and configuration.

show ipv6 neighbors

Displays IPv6 neighbor cache entries.

show ipv6 prefix-list

Displays a list of IPv6 prefix lists.

show ipv6 protocols

Displays a list of IPv6 routing protocols on the switch.

show ipv6 rip

Displays IPv6 RIP routing protocol status.

show ipv6 route

Displays IPv6 route table entries.

show ipv6 static

Displays IPv6 static routes.

show ipv6 traffic

Displays IPv6 traffic statistics.

Configuration Examples for IPv6 Unicast Routing

- Example: Configuring IPv6 Addressing and Enabling IPv6 Routing

- Example: Configuring IPv6 ICMP Rate Limiting

- Example: Configuring Static Routing for IPv6

- Example: Displaying IPv6

Example: Configuring IPv6 Addressing and Enabling IPv6 Routing

This example shows how to enable IPv6 with both a link-local address and a global address based on the IPv6 prefix 2001:0DB8:c18:1::/64. The EUI-64 interface ID is used in the low-order 64 bits of both addresses. Output from the show ipv6 interface EXEC command is included to show how the interface ID (20B:46FF:FE2F:D940) is appended to the link-local prefix FE80::/64 of the interface.

Device(config)# ipv6 unicast-routing
Device(config)# interface gigabitethernet 1/0/11
Device(config-if)# ipv6 address 2001:0DB8:c18:1::/64 eui 64
Device(config-if)# end
Device# show ipv6 interface gigabitethernet 1/0/11
GigabitEthernet1/0/11 is up, line protocol is up
IPv6 is enabled, link-local address is FE80::20B:46FF:FE2F:D940
Global unicast address(es):
2001:0DB8:c18:1:20B:46FF:FE2F:D940, subnet is 2001:0DB8:c18:1::/64 [EUI]
Joined group address(es):
FF02::1
FF02::2
FF02::1:FF2F:D940
MTU is 1500 bytes
ICMP error messages limited to one every 100 milliseconds
ICMP redirects are enabled
ND DAD is enabled, number of DAD attempts: 1
ND reachable time is 30000 milliseconds
ND advertised reachable time is 0 milliseconds
ND advertised retransmit interval is 0 milliseconds
ND router advertisements are sent every 200 seconds
ND router advertisements live for 1800 seconds
Hosts use stateless autoconfig for addresses.

Example: Configuring IPv6 ICMP Rate Limiting

This example shows how to configure an IPv6 ICMP error message interval of 50 milliseconds and a bucket size of 20 tokens.

Device(config)#ipv6 icmp error-interval 50 20

Example: Configuring Static Routing for IPv6

This example shows how to configure a floating static route to an interface with an administrative distance of 130:

Device(config)# ipv6 route 2001:0DB8::/32 gigabitethernet 1/0/1 130

Example: Displaying IPv6

This is an example of the output from the show ipv6 interface privileged EXEC command:

De# show ipv6 interface
Vlan1 is up, line protocol is up
IPv6 is enabled, link-local address is FE80::20B:46FF:FE2F:D940
Global unicast address(es):
3FFE:C000:0:1:20B:46FF:FE2F:D940, subnet is 3FFE:C000:0:1::/64 [EUI]
Joined group address(es):
FF02::1
FF02::2
FF02::1:FF2F:D940
MTU is 1500 bytes
ICMP error messages limited to one every 100 milliseconds
ICMP redirects are enabled
ND DAD is enabled, number of DAD attempts: 1
ND reachable time is 30000 milliseconds
ND advertised reachable time is 0 milliseconds
ND advertised retransmit interval is 0 milliseconds
ND router advertisements are sent every 200 seconds
ND router advertisements live for 1800 seconds
<output truncated>

Feature History and Information for IPv6 Unicast Routing

The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

Use the Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.

Feature Name

Release

Modification

IPv6 Unicast Routing

Cisco IOS Release 15.2(7)E1

This feature was introduced.

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