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300-410 Practice Question: An engineer configures a BGP route reflector in a…
An engineer configures a BGP route reflector in a network. After configuration, some iBGP routes are being dropped, causing routing loops. Which is the most likely explanation?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The route reflector is configured with the same cluster ID as another route reflector in the same AS.
BGP route reflectors use the ORIGINATOR_ID and CLUSTER_LIST attributes to prevent loops. If a route reflector receives a route with its own CLUSTER_LIST or ORIGINATOR_ID, it will drop the route. This can happen if there is a misconfiguration where the route reflector's cluster ID is not unique, or if a route reflector reflects a route back to the client that originated it, causing a loop.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
The route reflector is configured with the same cluster ID as another route reflector in the same AS.
Why this is correct
If two route reflectors share the same cluster ID, a route reflected by one may be dropped by the other because it sees its own cluster ID in the CLUSTER_LIST, preventing proper propagation and potentially causing loops.
- ✗
The next-hop-self command is not configured on the route reflector.
Why it's wrong here
Missing next-hop-self would cause reachability issues but not route dropping due to loop prevention.
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The BGP synchronization rule is enabled.
Why it's wrong here
Synchronization is disabled by default in modern IOS versions and would not cause route dropping by the route reflector.
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The route reflector is not a client of itself.
Why it's wrong here
Route reflectors do not need to be clients of themselves; this is not a valid configuration requirement.
Go deeper
Related to this question
Learn chapter
Introduction to ENARSI Exam and Network Fundamentals
Key term
BGP Route Reflector
A BGP Route Reflector is a networking device that reduces the number of BGP peer connections needed in a large network by allowing routers to share routing information without needing to connect to every other router directly.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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