Before EIGRP can send or receive any updates, routers must establish adjacencies with their neighbors. EIGRP routers establish adjacencies with neighbor routers by exchanging EIGRP Hello packets.

Use the show ip eigrp neighbors command to view the neighbor table and verify that EIGRP has established an adjacency with its neighbors. For each router, you should be able to see the IPv4 address of the adjacent router and the interface that this router uses to reach that EIGRP neighbor. Using this topology, each router has two neighbors listed in the neighbor table.

The show ip eigrp neighbors command output includes:

The show ip eigrp neighbors command is very useful for verifying and troubleshooting EIGRP. If a neighbor is not listed after adjacencies have been established with a router’s neighbors, check the local interface to ensure it is activated with the show ip interface brief command. If the interface is active, try pinging the IPv4 address of the neighbor. If the ping fails, it means that the neighbor interface is down and must be activated. If the ping is successful and EIGRP still does not see the router as a neighbor, examine the following configurations: