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300-410 Practice Question: Is troubleshooting BGP route summarization on a…
A network engineer is troubleshooting BGP route summarization on a border router that advertises a summary route 172.16.0.0/16 to an ISP neighbor. The engineer notices that the ISP is receiving the summary route but also receiving the more specific routes (172.16.1.0/24, 172.16.2.0/24), causing suboptimal routing. What should the engineer do to ensure only the summary route is advertised?
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
✓
Use the 'aggregate-address 172.16.0.0 255.255.0.0 summary-only' command under the BGP process.
In BGP, to suppress more specific routes when advertising a summary, the engineer must use the 'aggregate-address' command with the 'summary-only' keyword.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Configure the 'network' command for the summary route and remove the network statements for the specific subnets.
Why it's wrong here
Incorrect. Removing network statements for specific subnets may cause them to not be injected into BGP, but the summary route may still not be generated.
- ✓
Use the 'aggregate-address 172.16.0.0 255.255.0.0 summary-only' command under the BGP process.
Why this is correct
Correct. The aggregate-address with summary-only keyword creates the summary and suppresses all more specific routes from being advertised.
- ✗
Apply a route-map to the neighbor to filter out the specific routes using an ACL.
Why it's wrong here
Incorrect. While filtering can work, it is not the best practice; the aggregate-address command is designed for this purpose.
- ✗
Configure the 'summary-address' command under the BGP process.
Why it's wrong here
Incorrect. The 'summary-address' command is used in OSPF, not BGP.
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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.