mediumMultiple ChoiceObjective-mapped
300-410 Practice Question: Is troubleshooting a BGP session that is flapping
A network engineer is troubleshooting a BGP session that is flapping. The routers are connected via a direct Ethernet cable. BFD is configured for the BGP session. The engineer checks the BFD session and sees it is 'Up'. However, the BGP session goes down every 30 seconds. The BGP configuration includes 'neighbor 10.0.0.2 fall-over bfd'. What is the most likely cause?
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 BGP hold timer is set to 30 seconds on one router and 90 seconds on the other.
The BGP fall-over bfd command causes BGP to monitor the BFD session. If the BFD session is up but BGP is flapping, the issue is likely a BGP configuration problem, such as a mismatch in hold timer or update-source.
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 BGP hold timer is set to 30 seconds on one router and 90 seconds on the other.
Why this is correct
A mismatch in BGP hold timer can cause the session to reset when the hold timer expires; the BFD session being up does not affect BGP's own keepalive mechanism.
- ✗
The BFD session is using echo mode, which is not supported for BGP fall-over.
Why it's wrong here
Echo mode is supported and does not cause BGP flapping.
- ✗
The interface is configured with 'bfd interval 50 min_rx 50 multiplier 3' but the neighbor is configured with 'bfd interval 100 min_rx 100 multiplier 3'.
Why it's wrong here
BFD parameter negotiation allows different values; as long as the session is up, this is not the issue.
- ✗
The BGP session is using EBGP multihop, and the TTL is set to 2.
Why it's wrong here
If the routers are directly connected, EBGP multihop is not needed; TTL mismatch would prevent BGP from forming, not cause flapping.
Go deeper
Related to this question
About these practice questions
Courseiva writes every 300-410 question from scratch — 1,966 in total, each with an explanation and a wrong-answer breakdown. None are copied from real exams or dumps. Learn why practice questions differ from exam dumps →
JA
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.