200-301 Question 336
Single answerTwo routers, R1 and R2, are configured as OSPF neighbors on the same broadcast network. Despite having matching OSPF settings (area, network type, and authentication), the routers are not forming a full neighbor adjacency. Upon investigation, it is found that R1 is stuck in the 'Init' state. What is the most likely cause of the problem?
- A
R1 has not received a Hello packet from R2.
- B
The OSPF Router IDs on R1 and R2 are the same.
- C
R2 is configured with a passive interface for the connected subnet.
- D
The MTU settings on R1 and R2 are mismatched.
Show answer and explanation
Correct answer: A
Explanation
In OSPF, the 'Init' state indicates that a router has sent Hello packets but has not received any Hello packets from its neighbor. This points to a communication issue, such as R1 not receiving Hello packets from R2. The other options either describe issues that occur in later stages of the adjacency process or are not relevant to the 'Init' state.
- A. Correct.
When a router is stuck in the 'Init' state, it means that it has sent Hello packets but has not received any Hello packets in return from its neighbor. This is the most likely cause in this scenario.
- B. Incorrect.
While having the same OSPF Router IDs can cause issues with adjacency, it typically results in a different state, such as '2WAY' or no adjacency at all, rather than being stuck in 'Init'.
- C. Incorrect.
A passive interface configuration prevents OSPF Hello packets from being sent, but in this case, R1 is stuck in 'Init', which implies it is sending Hello packets but not receiving any. Thus, this is less likely the cause.
- D. Incorrect.
Mismatched MTU settings can prevent an OSPF adjacency from reaching the 'Full' state, but it would not cause a router to be stuck in 'Init'. Instead, mismatched MTU usually results in issues during the 'ExStart' state.