hardMultiple ChoiceObjective-mapped
300-410 Practice Question: An engineer configures a route reflector cluster…
An engineer configures a route reflector cluster with two route reflectors in the same cluster ID. After convergence, some iBGP routes are missing on clients, and 'show ip bgp' shows the path with 'r' flag. What 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 cluster ID is misconfigured and should be unique per route reflector.
When two route reflectors share the same cluster ID, they treat each other's updates as if from the same cluster. The route reflector loop prevention mechanism drops routes learned from another RR in the same cluster, causing route loss if the clients are not fully meshed.
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 cluster ID is misconfigured and should be unique per route reflector.
Why this is correct
Route reflectors with the same cluster ID will reject routes from each other to prevent loops, leading to missing routes on clients.
- ✗
The route reflectors have different BGP AS numbers, causing the 'r' flag to indicate a routing loop.
Why it's wrong here
Different AS numbers would not cause the 'r' flag; that flag indicates the route was received from a route reflector in the same cluster.
- ✗
The clients have 'no bgp default route-reflector-client' configured, preventing them from receiving reflected routes.
Why it's wrong here
This command is not valid; clients are defined under the neighbor statement with 'route-reflector-client'.
- ✗
The route reflectors have 'bgp cluster-id' set to 0.0.0.0, which disables cluster-based loop prevention.
Why it's wrong here
Setting cluster-id to 0.0.0.0 is not allowed; the default cluster ID is the router ID.
Go deeper
Related to this question
Learn chapter
OSPF Route Summarization and Filtering
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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