Common IGP Routing Protocol Issues, Causes, and Solutions
Advertised network interface is down

IGP routing protocols will not advertise any interface network address that is physically down.

This example shows two routers running RIP between each other.

Debugs and Verification
Figure shows that interface Ethernet 0 is down.

Figure shows the output from the debug ip rip command. In this debug, router R1 is not sending or receiving any RIP updates because Layer 2 is down. There is no output from this debug command because of this problem.

Solution
RIP cannot send or receive any routes if Layer 2 is down. To correct this problem, Layer 2 or Layer 1 must be corrected.

Figure shows the interface Ethernet 0 after fixing the Layer 2 problem.

Figure shows the routing table of router R2.