Restrictions for Implementing EIGRP for IPv6
This section lists ways in which EIGRP for IPv6 differs from EIGRP for IPv4 and lists EIGRP for IPv6 restrictions:
1. EIGRP for IPv6 is directly configured on the interfaces over which it runs. This feature allows EIGRP for IPv6 to be configured without the use of a global IPv6 address. There is no network statement in EIGRP for IPv6.
2. In per-interface configuration at system startup, if EIGRP has been configured on an interface, then the EIGRP protocol may start running before any EIGRP router mode commands have been executed.
3. An EIGRP for IPv6 protocol instance requires a router ID before it can start running. EIGRP for IPv6 has a shutdown feature. The routing process should be in "no shutdown" mode in order to start running.
4. When a user uses a passive-interface configuration, EIGRP for IPv6 need not be configured on the interface that is made passive. EIGRP for IPv6 provides route filtering using the distribute-list prefix-list command. Use of the route-map command is not supported for route filtering with a distribute list.
EIGRPv6 involves the following configuration steps
1. To enable EIGRPv6 on a router interface, use the command "ipv6 eigrp" as on individual interfaces that will be part of the EIGRPv6 process.
2. Enable IPv6 routing using "ipv6 unicast-routing" command.
3. Create an EIGRPv6 process using "ipv6 router eigrp <asn>" command.
4. Assign an EIGRPv6 router ID using the "eigrp router-id <router-id>" command in router configuration mode.
5. Enable EIGRPv6 on interfaces using the "ipv6 eigrp <asn>" command in interface configuration mode.
6. The command ipv6 eigrp <as-number> enables EIGRP for IPv6 on a specified interface. And the command ipv6 router eigrp <as-number> enters router configuration mode and creates an EIGRP IPv6 routing process.
7. The command eigrp router-id <ip-address> enables the use of a fixed router ID. Use this command only if an IPv4 address is not defined on the router eligible for router ID. The "AS" stands for Autonomous System number. This number should be the same on all routers.
The following are the key points that you may need to remember with respect to forming neighbor relationship in EIGRP-IPV6:
1. The interfaces must be in up state. (true for both ipv6 and ipv4)
2. IPv6 addresses need not be in the same subnet for forming neighbor relationship. Note that in EIGRP ipv4, the neighbor interfaces should be on the same subnet.
3. Both devices should use the same Autonomous System Number (ASN).
4. ACLs should not be filtering routing messages. This is true for ipv4 also.
5. Must be able to pass routing protocol authentication, if configured. This is true for Ipv4 also.
6. K values must match (true for ipv4 also)
7. Hello and Hold timers need NOT match (for both ipv4 and ipv6)
8. EIGRP-IPV6 denotes EIGRP route with the letter "D", and not "E" as in the case of EIGRP ipv4.
EIGRPv6 show commands:
show ipv6 eigrp traffic: Displays the number of EIGRP IPv6 packets sent and received, to used in user EXEC or privileged EXEC mode.
show ipv6 eigrp neighbors: The show ipv6 eigrp neighbors command lists each neighbor using link-local IPv6 address along with local interface.
show ipv6 eigrp interfaces command shows three interfaces that have EIGRPv6 enabled Note that the command does not show eigrp interfaces that had been configured as passive interface.
show ipv6 eigrp topology: This command displays entries in the EIGRP IPv6 topology table The “show ipv6 eigrp topology” command can be used without any keywords or arguments. If this command is used without any keywords or arguments, then only routes that are feasible successors are displayed.
