Common IGP Routing Protocol Issues, Causes, and Solutions
Passive interface

The passive-interface command works differently with the different IP routing protocols that support it.

  • RIP– With, routing updates are received, but are not sent.
  • EIGRP – With EIGRP, the router stops sending hello packets on passive interfaces. When this happens, EIGRP cannot form neighbor adjacencies on the interface, and routing updates can neither be sent nor received.
  • OSPF – With OSPF, routing information is neither sent nor received on a passive interface. The network address of the passive interface appears as a stub network in the OSPF domain.

Debugs and Verification
Figure shows the output of the show ip protocols command, which shows the outgoing interface is defined as passive.

Figure shows the configuration of router R1, which shows that the outgoing interface is defined as passive.

Solution
Figures and confirm that the interface Ethernet 0 is defined as passive, so router R1 is not sending any updates on Ethernet 0. Sometimes, it is desirable for some networks to be advertised and others to be filtered. In this situation, a distribute-list out would be a better solution.

In this example, the assumption is that the passive-interface was configured by mistake, and this command needs to be removed to solve this problem. Figure shows the new configuration to solve this problem.

Figure shows the routing table entry on router R2 after fixing the problem.