350-401 Question 431
Select 2An enterprise network engineer is configuring OSPF between two routers (R1 and R2). The OSPF adjacency fails to form even though both routers are on the same subnet and have matching OSPF area IDs. Upon investigation, the engineer notices that OSPF authentication is enabled on R1 but not on R2. What steps should the engineer take to successfully establish the OSPF neighbor relationship?
- A
Enable OSPF authentication on R2 and configure the same authentication type and key on both R1 and R2.
- B
Disable OSPF authentication on R1 to match the configuration on R2.
- C
Ensure both R1 and R2 are using the same OSPF router ID.
- D
Verify and configure the same OSPF hello and dead intervals on both R1 and R2.
- E
Enable MD5 authentication on both routers and configure a different authentication key for each router.
Show answer and explanation
Correct answers: A, D
Explanation
For OSPF neighbor relationships to form, the configurations on both routers must match in key parameters such as OSPF authentication type and key, as well as hello and dead intervals. Enabling OSPF authentication on R2 and ensuring the same intervals are configured on both routers resolves the issue without compromising network security.
- A. Correct.
This is correct. For OSPF neighbors to form an adjacency, both routers must have the same authentication type and key configured if authentication is enabled.
- B. Incorrect.
While disabling OSPF authentication on R1 would allow the adjacency to form, this is not a recommended approach in enterprise environments where security is a concern.
- C. Incorrect.
The OSPF router ID is important for routing decisions but does not affect the formation of OSPF neighbor adjacencies. OSPF neighbors can form even with different router IDs.
- D. Correct.
This is correct. OSPF hello and dead intervals must match between neighbors to successfully form an adjacency.
- E. Incorrect.
This is incorrect. While MD5 authentication is a valid method, both routers must use the same authentication key for the adjacency to form.