Question

You are troubleshooting an OSPFv2 area 0 that spans four routers on IOS XR. Users report intermittent reachability to prefixes advertised by R3. On R1 you notice the SPF calculation runs repeatedly, and 'show ospf database router' displays two Type-1 LSAs with the same Router ID (10.0.0.3) but originating from different interfaces and with conflicting link information. Adjacencies flap on R3 and R4. What is the most likely root cause of this instability?

Accepted Answer

Two routers in area 0 have been configured with the same OSPF Router ID, causing LSA ID collisions and continuous SPF recalculation.

Answer

R3 is missing the 'network' statement for the link to R4, so its Type-1 LSA is incomplete.

Answer

The area 0 routers have mismatched MTU values, preventing the LSDB from fully synchronizing.

Answer

An OSPF authentication key mismatch on R3 is corrupting the Type-1 LSA payload.