hardMultiple ChoiceObjective-mapped
300-410 Practice Question: An engineer configures a route map to filter BGP…
An engineer configures a route map to filter BGP routes based on AS-path using a regex. The route map is applied inbound to an eBGP neighbor. The engineer notices that routes with an AS-path containing the neighbor's AS are still being accepted. 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 AS-path is prepended with the local AS before the inbound route map is applied, so the regex does not match the original AS-path.
When an eBGP route is received, the router prepends its own AS to the AS-path before the route map is applied. Therefore, if the route map is trying to match the neighbor's AS in the AS-path, it will fail because the neighbor's AS is now the first AS in the path. The edge case is that the AS-path is modified before the route map is processed.
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 AS-path is prepended with the local AS before the inbound route map is applied, so the regex does not match the original AS-path.
Why this is correct
eBGP prepends the local AS before route map processing; the route map sees the modified path.
- ✗
The route map is applied outbound instead of inbound.
Why it's wrong here
Outbound would affect routes sent, not received.
- ✗
The regex is incorrect; it should use _AS_ to match the AS number.
Why it's wrong here
Even with correct regex, the AS is prepended, so the neighbor's AS is not the first.
- ✗
The neighbor is configured with 'send-community' which overrides the route map.
Why it's wrong here
Send-community does not affect AS-path filtering.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 300-410 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 300-410 exam.