- EIGRP for IPv6 advertises IPv6 prefixes/lengths, rather than IPv4 subnet/mask information.
- EIGRP for IPv6 uses the neighbor’s link local address as the next-hop IP address; EIGRP for IPv4 has no equivalent concept.
- EIGRP for IPv6 encapsulates its messages in IPv6 packets, rather than IPv4 packets.
- Like RIPng and OSPFv3, EIGRP for IPv6 authentication relies on IPv6’s built-in authentication and privacy features.
- EIGRP for IPv4 defaults to use automatic route summarization at the boundaries of classful IPv4 networks; IPv6 has no concept of classful networks, so EIGRP for IPv6 cannot perform any automatic summarization.
- EIGRP for IPv6 does not require neighbors to be in the same IPv6 subnet as a requirement to become neighbors.
- EIGRP for IPv6 uses Multicast Update address of FF02::10, instead of 224.0.0.10.
EIGRP for IPv6 follows the same basic configuration style as for RIPng, plus a few additional steps, as follows:
Step 1. Enable IPv6 routing with the ipv6 unicast-routing global command.
Step 2. Enable EIGRP using the ipv6 router eigrp {1 – 65535} global configuration command.
Step 3. Enable IPv6 on the interface, typically with one of these two methods:
- Configure an IPv6 unicast address on each interface, using the ipv6 address address/prefix-length [eui-64] interface command.
- Configure the ipv6 enable command, which enables IPv6 and causes the router to derive its link local address.
Step 4. Enable EIGRP on the interface with the ipv6 eigrp asn interface subcommand (where the name matches the ipv6 router eigrp asn global configuration command).
Step 5. Enable EIGRP for IPv6 with a no shutdown command while in EIGRP configuration mode.
Step 6. If no EIGRP router ID has been automatically chosen, due to not having at least one working interface with an IPv4 address, configure an EIGRP router ID with the eigrp router-id rid command in EIGRP configuration mode.
Note: At Step 5, IOS supports the ability to stop and start the EIGRP process with the shutdown and no shutdown router mode subcommands. After initial configuration, the EIGRP for IPv6 process starts in shutdown mode, so to make the process start, IOS requires a no shutdown command.
Note: The EIGRP for IPv6 process must have a router ID (RID) before the process works. EIGRP for IPv6 uses the same process as EIGRP for IPv4 for choosing the RID.
The following list defines how EIGRP for IPv6 picks its RID, listed in the order of preference:
Step 1. Use the configured value (using the eigrp router-id a.b.c.d EIGRP subcommand under the ipv6 router eigrp command).
Step 2. Use the highest IPv4 address on an up/up loopback interface.
Step 3. Use the highest IPv4 address on an up/up non-loopback interface.
Note: After being enabled on an interface, EIGRP for IPv6 performs the same two basic tasks as it does with EIGRP for IPv4: it discovers neighbors and advertises about connected subnets.
Due to the fact that in our topology we are using an IOS version which does not support EIGRPv6, below you can find an example of EIGRPv6 configuration from CCNP ROUTE 642-902 Official Certification Guide, Wendell Odom, Cisco Press, page 584:
! Configuration step 1: enabling IPv6 routing
ipv6 unicast-routing
! Next, configuration steps 3 and 4, on 5 different interfaces
interface FastEthernet0/0.1
ipv6 address 2012::1/64
ipv6 eigrp 9
!
interface FastEthernet0/0.2
ipv6 address 2017::1/64
ipv6 eigrp 9
!
interface FastEthernet0/1.18
ipv6 address 2018::1/64
ipv6 eigrp 9
!
interface Serial0/0/0.3
ipv6 address 2013::1/64
ipv6 eigrp 9
!
interface Serial0/0/0.4
!
ipv6 address 2014::1/64
ipv6 eigrp 9
interface Serial0/0/0.5
ipv6 address 2015::1/64
ipv6 eigrp 9
! Configuration steps 2, 5, and 6
ipv6 router eigrp 9
no shutdown
router eigrp 10.10.34.3
In our case, the IOS version is:
R3#show version
Cisco IOS Software, 2600 Software (C2691-ADVENTERPRISEK9-M), Version 12.4(25c), RELEASE SOFTWARE (fc2)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2010 by Cisco Systems, Inc.
The following link shows the IOS versions which support EIGRPv6:
http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipv6/command/ipv6-cr-book/ipv6-i1.html#wp5867267730
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