300-410 Question 149
Single answerA network engineer is configuring a BGP route reflector to simplify the topology and reduce the number of iBGP sessions in an enterprise network. The engineer notices that one client router is not receiving routes from other client routers in the same cluster. What is the most likely reason for this issue?
- A
The route reflector is not configured to reflect routes between client routers.
- B
The client router does not have an active iBGP session with the route reflector.
- C
The route reflector is not advertising routes to external BGP peers.
- D
The cluster ID for the route reflector is missing or incorrectly configured.
Show answer and explanation
Correct answer: B
Explanation
In a route reflector setup, client routers rely on an active iBGP session with the route reflector to receive routes from other clients. If this session is not established or is inactive, the route reflector cannot reflect routes between the clients. The other options either describe irrelevant issues or misunderstand the behavior of route reflectors in BGP.
- A. Incorrect.
Incorrect. A route reflector automatically reflects routes between client routers, so no additional configuration is required for this functionality.
- B. Correct.
Correct. For a client router to receive routes via the route reflector, it must have an active iBGP session with the route reflector. Without this session, routes cannot be exchanged.
- C. Incorrect.
Incorrect. The issue described pertains to iBGP route reflection within the cluster, not to eBGP advertisement of routes.
- D. Incorrect.
Incorrect. While an incorrect or missing cluster ID can cause issues in certain scenarios, it does not prevent a route reflector from reflecting routes within a cluster.