Part 2: Implement EIGRP for IPv6 and Named EIGRP

In this part of the lab, you will configure and verify EIGRP in the network. Routers R1 and R3 will used Named EIGRP, while router R2 will use Classic EIGRP. After you have established the network, you will examine the differences in how each version of EIGRP deals with metrics.

For the lab, you will use the Autonomous System number 43 on all routers.

Step 1: Configure EIGRP for IPv6 on R2

a.     Start the configuration of Classic EIGRP by issuing the ipv6 router eigrp 43 command.

Open configuration window

b. Configure the EIGRP Router ID using the eigrp router-id command. Use the number 2.2.2.2 for R2.

c. Identify the interfaces that should be configured with EIGRP and the networks that should be included in the EIGRP topology table. This is done on the interfaces with the ipv6 eigrp command.

d.     Verify the interfaces now involved in EIGRP with the show ipv6 eigrp interfaces command.

Close configuration window

Step 2: Configure Named EIGRP for IPv6 on R1 and R3

a.     Start the configuration of Named EIGRP by issuing the router eigrp [ name ] command. The name parameter can be a number, but the number does not identify an Autonomous System as it does with Classic EIGRP, it simply identifies the process. For our purposes, name the process EIGRP_IPV6.

Open configuration window

a. Enter into address-family configuration mode with the address-family ipv6 unicast autonomous-system 43 command. It is not necessary to configure EIGRP for IPv6 on the interfaces. In named-mode configuration, EIGRP for IPv6 is automatically enabled on all interfaces that are configured with an IPv6 address.

c.     Configure the EIGRP Router ID using the eigrp router-id command. Use the number 1.1.1.1.

d.     Repeat the configuration process on R3 and D2. For the R3 router ID use 3.3.3.3, and for the D2 router ID use 132.132.132.132.

Step 3: Verify EIGRP for IPv6

a.     A few seconds after configuring the network statements on R1, R3 and D2, you should have seen EIGRP adjacencies being formed, as noted at the console by messages similar to the one below.

*Mar  9 13:42:47.969: %DUAL-5-NBRCHANGE: EIGRP-IPv6 43: Neighbor FE80::3:2 (GigabitEthernet0/0) is up: new adjacency

b.     To verify that routing is working, ping from PC1 to Interface Loopback 1 on R3 (2001:db8:abcd:8::1). The ping should be successful.

c.     On R1, examine the EIGRP entries in the IPv6 routing table using the show ipv6 route eigrp command. As you can see, R1 is aware of all of the networks that have been configured in the topology. The remote networks that were learned from EIGRP and that appear in the routing table were learned from routers R2 and R3 as indicated by the link local address that is displayed for these entries. Note that in some cases, EIGRP for IPv6 has two equal cost routes for a network.

d.     Now examine the EIGRP topology table using the show ipv6 eigrp topology all-links command. The all-links parameter instructs the router to display routes that are not successors or feasible successors. We will focus on the routes to 2001:db8:abcd:10::/64 and 2001:db8:cafe:2::/64. There are several things to notice.

Remember that the topology table is EIGRP’s database of route information. EIGRP selects the best paths, based on the DUAL algorithm, and offers them to the IP routing table. However, the IP routing table does not have to use those offered paths, because the router may have learned about the same network from a more reliable routing source, which would be a routing source with a lower administrative distance.

We will focus on the routes, highlighted in the above output, to 2001:db8:abcd:10::/64 and 2001:db8:cafe:2::/64. There are several things to notice:

o    The entry for the 2001:db8:abcd:10::/64 network shows two successors, while the entry for 2001:db8:cafe:2::/64 shows only one successor. Both entries show two paths. The path with the lowest Feasible Distance (FD) is selected as the successor and is offered to the routing table. For 2001:db8:abcd:10::/64, there are two paths with equal FD, so they are both successors and both are offered to the global routing table. In the case of 2001:db8:cafe:2::/64, the FD is listed as 19660800. The path via fe80::2:1 shows that number as the FD (first number in parentheses). The path via fe80::d1:1 shows an FD of 2621440, which is higher than the current FD. So that path, although valid, is a higher cost path and is not offered to the routing table.

o    The FD listed in the topology table does not match the metric listed in the routing table. For 2001:db8:abcd:10::/64, the routing table shows the metric value 16000 while the topology table shows the FD as 2048000. This is due to the routing table having a limit of 4 bytes (32 bits) for metric information, while EIGRP on R1 is using EIGRP wide metrics, which are 64 bits. Wide metrics are used by Named EIGRP by default. To work around the 32-bit metric size limitation in the routing table, EIGRP divides the wide-metric value by the EIGRP_RIB_SCALE value, which defaults to 128. The value 2048000 divided by 128 is 16000.

      Note: A network with mixed EIGRP implementations (Named and Classic in the same routing domain), will have some loss of route clarity, which could lead to sub-optimal path selection. The recommended implementation is to use Named EIGRP in all cases.

o    There are no feasible successors listed in the topology table for 2001:db8:abcd:10::/64 or 2001:db8:cafe:2::/64. The feasibility condition requires that the reported distance (RD) to a destination network be less than the current FD for a next-hop to be considered a feasible successor to the route. In the case of 2001:db8:cafe:2::/64, the RD of the path via fe80::d1:1 is listed as 1966080, which is equal to the current FD, which disqualifies this path as a feasible successor. If the path via fe80::2:1 were to be lost, R1 would have to send queries to find a new way to get to 2001:db8:cafe:2::/64. Feasible successors appear only in the topology table. Only successors appear in the routing table.

      e.     To see the RIB Scale and metric version values, as well as other protocol information, issue the show ipv6 protocols | section EIGRP_IPv6 command.

f. To examine details about a particular path, issue the show ipv6 eigrp topology [address] command. Among other things in this output, you can see the values used in calculating the metric.