300-410 Question 84
Select 4A network engineer is troubleshooting an OSPFv2 routing issue between RouterA and RouterB. OSPF is configured on both routers, but RouterA is not forming a neighbor relationship with RouterB. The engineer runs the command show ip ospf neighbor on RouterA and notices that no neighbors are listed. What could be the issue?
- A
The OSPF hello timer on RouterA does not match the hello timer on RouterB.
- B
The OSPF process ID configured on RouterA is different from the one on RouterB.
- C
RouterA and RouterB are not in the same OSPF area.
- D
The interfaces on RouterA and RouterB are configured with different MTU values.
- E
The OSPF network types on RouterA and RouterB are mismatched.
Show answer and explanation
Correct answers: A, C, D, E
Explanation
To troubleshoot OSPF neighbor issues, several factors must be verified, including matching hello/dead timers, OSPF area configuration, MTU settings, and network types. While the OSPF process ID is locally significant and does not impact neighbor formation, mismatches in other parameters like timers, areas, MTU, or network types can prevent OSPF neighbors from establishing adjacency.
- A. Correct.
Correct: OSPF requires that the hello and dead timers match between neighbors. A mismatch in the hello timer will prevent the routers from forming a neighbor relationship.
- B. Incorrect.
Incorrect: The OSPF process ID is locally significant and does not need to match between routers to form a neighbor relationship.
- C. Correct.
Correct: OSPF neighbors must be in the same area to establish a neighbor relationship. If RouterA and RouterB are in different areas, they will not become neighbors.
- D. Correct.
Correct: A mismatch in MTU settings between OSPF neighbors can prevent the adjacency from forming, as OSPF packets may be dropped.
- E. Correct.
Correct: OSPF network types (e.g., broadcast, point-to-point) must match between neighbors. A mismatch in network types can prevent neighbor formation.