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300-410 R1 and R2 are BGP peers with BFD enabled Practice Question
R1 and R2 are BGP peers with BFD enabled. R1#show bgp neighbors 10.1.1.2 shows BGP state 'Active' and BFD session 'Down'. R2#show bfd neighbors shows the session as 'Up' with R1. R1 has 'neighbor 10.1.1.2 fall-over bfd' configured. R2 has 'neighbor 10.1.1.1 fall-over bfd' configured. The link between them is stable. What is the root 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
✓
R1 is missing 'bfd interval' configuration on the interface facing R2.
BFD for BGP fall-over requires that the BFD session be established before BGP can form. If the BFD session is up on R2 but down on R1, it indicates a unidirectional issue. This can happen if R1 has an ACL blocking BFD control packets from R2, or if R1's BFD configuration is missing. Here, R1 likely lacks 'bfd interval' configuration on the interface, causing BFD to not initiate.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
R1 is missing 'bfd interval' configuration on the interface facing R2.
Why this is correct
Without BFD interval configuration on the interface, R1 cannot establish a BFD session, causing BGP fall-over to keep BGP in Active state.
- ✗
BGP requires 'neighbor 10.1.1.2 ebgp-multihop' for BFD to work.
Why it's wrong here
Multihop is not needed for directly connected peers.
- ✗
R2 has a higher BFD multiplier causing session failure.
Why it's wrong here
BFD session is up on R2, so multiplier is not an issue.
- ✗
The BGP update-source is not set to the interface IP.
Why it's wrong here
Update-source does not affect BFD session establishment.
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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.