Neighbor Command on CISCO Router/Switch

Command

Neighbor

Use

This command tells EIGRP to communicate with unicast updates to a specific neighbor.

Syntax

Router(config-router)#neighbor <ip address> <interface>

Example

In this example, we will configure R4 to send its updates to R3 using unicast. Looking at the debug output for ip packets, we see that updates are currently being sent to EIGRP’s multicast address 224.0.0.10.

R4(config-router)#do debug ip packet
IP packet debugging is on

*Mar 1 00:33:43.071: IP: s=10.4.4.4 (local), d=224.0.0.10 (Serial0/0), len 60, sending broad/multicast
*Mar 1 00:33:43.079: IP: s=4.5.5.5 (local), d=224.0.0.10 (Loopback55), len 60, sending broad/multicast
*Mar 1 00:33:43.087: IP: s=4.5.5.5 (Loopback55), d=224.0.0.10, len 60, rcvd 2

We then configure R4, R1, and R3 to sent updates via unicast.

R4(config)#router rip
R4(config-router)#passive-interface default
R4(config-router)#neighbor 10.4.4.3
R4(config-router)#neighbor 10.4.4.1

Notice that updates are now being sent directly to R1 and R3.

*Mar 1 00:31:49.283: IP: s=10.4.4.3 (Serial0/0), d=10.4.4.4 (Serial0/0), len 40, rcvd 3
*Mar 1 00:31:49.343: IP: tableid=0, s=10.4.4.1 (Serial0/0), d=10.4.4.4 (Serial0/0), routed via RIB
*Mar 1 00:31:49.347: IP: s=10.4.4.1 (Serial0/0), d=10.4.4.4 (Serial0/0), len 69, rcvd 3
*Mar 1 00:31:49.363: IP: s=10.4.4.4 (local), d=10.4.4.1 (Serial0/0), len 40, sending

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