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10.7 EIGRPv6

Like OSPFv3 compared to OSPFv2, EIGRP for IPv6 has a great deal in common with EIGRP for IPv4. In fact, EIGRP for IPv6 is very similar to EIGRP for IPv4. Of course, some differences exist, so this section covers the key differences before moving on to configuration.

10.7.1 Comparison of EIGRP for IPv4 and for IPv6

IPv6 EIGRP requires a routing process to be defined and enabled (no shutdown) and a router ID (in 32-bit IPv4 address format) to be manually assigned using the router-id command, both of which must be done in IPv6 router configuration mode before the IPv6 EIGRP routing process can start. These are two of the differences between EIGRP for IPv4 and IPv6. Some others include the following:

  • Configured on the interface- As with OSPFv3 (and RIPng), EIGRP advertises networks based on interface commands rather than routing process network commands. For example, the command to enable IPv6 EIGRP AS 100 on an interface is ipv6 eigrp 100.

  • Must no shut the routing process- When EIGRP for IPv6 is first configured on an interface, this action creates the IPv6 EIGRP routing process on the router. However, the routing process is initially placed in the shutdown state, and requires a no shutdown command in router configuration mode to become active.

  • Router ID- EIGRP for IPv6 requires a 32-bit router ID (a dotted-decimal IPv4 address) to be configured before it starts. A router does not complain about the lack of an EIGRP RID, however, so remember to configure one statically when doing a no shutdown in the routing process.

  • Passive interfaces- IPv6 EIGRP, passive interfaces are configured in the routing process only. That is, no related configuration commands are required on the interface.

  • Route filtering- IPv6 EIGRP performs route filtering using only the distribute-list prefix-list command.

  • Automatic summarization- IPv6 EIGRP has no equivalent to the IPv4 (no) auto-summary command, because there is no concept of classful routing in IPv6.

  • Cisco IOS support- EIGRP for IPv6 is supported in Cisco IOS beginning with Release 12.4(6)T.

Unchanged Features

All of the following EIGRP features work the same way in IPv6 as they do in IPv4. The only exceptions are the commands themselves, with ipv6 instead of ip in interface commands:

  • Metric weights

  • Authentication

  • Link bandwidth percentage

  • Split horizon

  • Next-hop setting, configured via the interface-level ipv6 next-hop-self eigrp as command

  • Hello interval and holdtime configuration

  • Address summarization (syntax differs slightly to accommodate IPv6 address format)

  • Stub networks (syntax and options differ slightly)

  • Variance

  • Most other features

IPv6 EIGRP uses authentication keys configured exactly as they are for IPv4 EIGRP.

Route Filtering

IPv6 EIGRP uses prefix lists for route filtering. To filter routes from EIGRP updates, configure an IPv6 prefix list that permits or denies the desired prefixes. Then apply it to the EIGRP routing process using the distribute-list prefix-list name command.

10.7.2 Configuring EIGRP for IPv6

The basic steps required to configure IPv6 EIGRP are quite similar to those for IPv4 EIGRP, with several additions:

Enable IPv6 unicast routing.

Configure EIGRP on at least one router interface.

In the EIGRP routing process, assign a router ID.

Issue the no shutdown command in the EIGRP routing process to activate the protocol. Use the relevant show commands to check your configuration.

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