Content

| 5.5 |  | Troubleshooting IGRP |
| 5.5.3 |  | Misconfigured neighbor statement |

By default, IGRP sends out its updates as a broadcast. IGRP provides a unicast method of sending IGRP updates using the neighbor statement. IGRP will not send the unicast update to the wrong neighbor or nonexistent neighbor. Figure shows two routers running IGRP between each other.

> Note: RIP v1 sends updates as broadcasts, whereas RIP v2, EIGRP, OSPF, and IS-IS use multicasts. The same neighbor statement can be used with RIP v1.

Debugs and Verification
Figure shows the IGRP configuration for router R1. The configuration shows that the neighbor statement is configured incorrectly. Instead of 131.108.1.2, as shown in Figure , the neighbor statement points to 131.108.1.3, which does not exist.

Solution
IGRP is sending a unicast update to 131.108.1.3, a neighbor that does not exist. To resolve this problem, the neighbor statement must be configured correctly.

Figure shows the correct configuration on router R1.

Figure shows the IGRP routes installed in the R2 routing table.