350-401 Question 476
Single answerA network engineer is troubleshooting a BGP neighbor relationship issue between two routers, R1 and R2. The routers are located in different Autonomous Systems (AS). Both routers are configured with a single-hop eBGP session. However, the BGP session is failing to establish. Upon investigation, the engineer discovers that the configurations include an explicit 'neighbor x.x.x.x ebgp-multihop 2' command. Which of the following actions will resolve the issue?
- A
Remove the 'ebgp-multihop 2' command from the configuration.
- B
Increase the TTL value in the 'ebgp-multihop' command to 3.
- C
Ensure that BGP authentication is configured on both routers.
- D
Disable the synchronization rule in BGP configuration.
Show answer and explanation
Correct answer: A
Explanation
In this scenario, the configuration of 'ebgp-multihop' is unnecessary because R1 and R2 are meant to establish a single-hop eBGP session. The 'ebgp-multihop' command is used when the eBGP neighbors are more than one hop away, and its inclusion here will prevent the session from forming. Removing the 'ebgp-multihop 2' command will allow the single-hop session to establish correctly.
- A. Correct.
Removing the 'ebgp-multihop 2' command is correct because a single-hop eBGP session does not require the 'ebgp-multihop' command. This command is unnecessary and will cause the session to fail.
- B. Incorrect.
Increasing the TTL value in the 'ebgp-multihop' command to 3 is incorrect because the session is intended to be a single-hop session; using 'ebgp-multihop' is not required at all in this scenario.
- C. Incorrect.
While BGP authentication is important, it is not relevant to this issue. The problem here is caused by the unnecessary 'ebgp-multihop' command, not the lack of authentication.
- D. Incorrect.
Disabling the synchronization rule is unrelated to this problem. Synchronization is primarily used in older BGP configurations to ensure consistency between BGP and IGP, and it does not impact the neighbor establishment in this scenario.