ANS-C01 Network Management and Operations Practice Question
A network engineer is troubleshooting intermittent connectivity issues between an EC2 instance in a VPC and an on-premises data center over a Direct Connect virtual interface. The engineer notices that the BGP session is flapping. Which configuration should the engineer verify first?
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
✓
Verify that the BGP hold timer and keepalive interval are consistent between the on-premises router and the AWS side.
BGP session flapping is often caused by mismatched BGP timers (hold timer and keepalive interval) between BGP peers. Verifying that these timers are consistent should be the first step. Option B is incorrect because MTU mismatch typically leads to packet loss or fragmentation, not BGP flapping. Option C is incorrect because advertising the correct prefix is necessary for route propagation, but BGP session stability depends on timer and configuration compatibility. Option D is incorrect because the virtual interface state being 'available' is a prerequisite, but if it is available, flapping suggests a higher-layer configuration issue.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Verify that the BGP hold timer and keepalive interval are consistent between the on-premises router and the AWS side.
Why this is correct
BGP timer mismatch causes session flapping.
- ✗
Verify that the MTU setting on the Direct Connect virtual interface matches the on-premises router.
Why it's wrong here
MTU mismatch causes packet loss, not BGP flap.
- ✗
Verify that the on-premises router is advertising the correct prefix to AWS.
Why it's wrong here
Route advertisement affects routing, not BGP session stability.
- ✗
Verify that the Direct Connect virtual interface is in the 'available' state.
Why it's wrong here
VIF state being available is necessary but not the cause of flapping.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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