300-410 Question 146
Single answerIn a BGP deployment, a route reflector is implemented to simplify the iBGP topology in a large network. Which of the following is true about how the route reflector processes and forwards BGP routes learned from its clients?
- A
The route reflector forwards all routes received from a client to all other clients without modification.
- B
The route reflector adds its own router ID to the Cluster List attribute of the route before forwarding it to prevent routing loops.
- C
The route reflector modifies the next-hop attribute of the received route to its own IP address before advertising it to other clients.
- D
The route reflector only forwards routes between its clients and non-client peers to reduce the number of advertised routes.
Show answer and explanation
Correct answer: B
Explanation
A BGP route reflector is designed to reduce the full-mesh requirement of iBGP. It processes and forwards routes according to specific rules. One of the key mechanisms to prevent routing loops in a route reflector environment is the use of the Cluster List attribute. The route reflector appends its own router ID to the Cluster List when advertising routes to its clients or peers. This ensures that if the route is seen again with the same Cluster ID, it will be discarded, thus preventing loops.
- A. Incorrect.
Incorrect. A route reflector does not forward all routes indiscriminately. It follows specific rules, such as checking the Cluster List to prevent routing loops.
- B. Correct.
Correct. The route reflector adds its router ID to the Cluster List attribute to prevent routing loops in a network with multiple route reflectors or redundant paths.
- C. Incorrect.
Incorrect. The route reflector does not modify the next-hop attribute unless explicitly configured using a next-hop-self command. By default, the next-hop attribute remains unchanged.
- D. Incorrect.
Incorrect. The route reflector forwards routes between its clients and peers as per the BGP route reflector rules and does not limit route forwarding for optimization purposes.