Cisco Certified Support Technician (CCST) NetworkingIP ConnectivityHard
A network technician is troubleshooting an IPv6 routing issue. Two directly connected routers, R1 and R2, are unable to establish an OSPFv3 adjacency. R1's interface is configured with 'ipv6 ospf 1 area 0'. R2's interface is configured with 'ipv6 ospf 1 area 1'. What is the most likely reason for the OSPFv3 adjacency failure?
- AMismatched OSPF area IDs.
- BIncorrect IPv6 addressing on the interfaces.
- CMismatched OSPF process IDs.
- DMissing OSPFv3 router ID configuration.
Show answer & explanationAnswer & explanation
Correct answer: A. Mismatched OSPF area IDs.
For OSPFv3 neighbors to form an adjacency, they must be in the same OSPF area on directly connected links. R1 is in Area 0, and R2 is in Area 1, which is a mismatch preventing adjacency formation.
Why the other options are wrong
- B. While incorrect IPv6 addressing would prevent communication, the provided configuration snippet points directly to an OSPF area mismatch as the most likely OSPF-specific cause.
- C. OSPF process IDs are locally significant and do not need to match between neighbors for adjacency.
- D. OSPFv3 requires a Router ID, but it can be automatically derived or manually configured. A missing Router ID might prevent full adjacency, but a direct area mismatch is a more fundamental showstopper.
OSPFv3 Adjacency Requirements
For OSPFv3 routers to form an adjacency, several parameters must match, including the OSPF area ID, authentication, and network type.
- Neighbors must be in the same OSPF area.
- Hello/Dead timers must match.
- Authentication (if used) must match.
- Network type must be compatible.
Memory trick: Areas Must Align, Or Adjacency Wont Shine.