200-301 Question 335
Single answerA network engineer is troubleshooting OSPF neighbor adjacency issues between two routers, R1 and R2. Both routers are directly connected, and their interfaces are in the same subnet. However, the OSPF neighbor adjacency is stuck in the 'INIT' state. What is the most likely cause of this issue?
- A
The OSPF hello and dead timers do not match between R1 and R2.
- B
The OSPF process ID is different on R1 and R2.
- C
The IP addresses of the interfaces are configured with different subnet masks.
- D
The OSPF area IDs are mismatched between R1 and R2.
Show answer and explanation
Correct answer: A
Explanation
In OSPF, hello and dead timers must match between neighboring routers for an adjacency to form. If they do not match, the routers can detect each other but cannot progress past the 'INIT' state. This makes Option 1 the correct choice. Other factors like mismatched area IDs or subnet masks would cause different types of failures, such as no adjacency forming at all.
- A. Correct.
If the OSPF hello and dead timers do not match between two routers, they will fail to form a neighbor adjacency and may remain stuck in the 'INIT' state.
- B. Incorrect.
The OSPF process ID is locally significant and does not need to match between routers for neighbor adjacencies to form.
- C. Incorrect.
A subnet mask mismatch would prevent the two routers from communicating at Layer 3 entirely, not just result in the OSPF adjacency being stuck in the 'INIT' state.
- D. Incorrect.
An OSPF area ID mismatch would prevent the adjacency from forming, but the state would likely remain in 'DOWN' rather than 'INIT'.