mediumMultiple Choice
300-410 Practice Question: Runs the following command to troubleshoot a BFD…
A network engineer runs the following command to troubleshoot a BFD issue:
R1# debug bfd event *Mar 1 00:12:34.567: BFD: [R1-to-R2] state DOWN -> UP (async) *Mar 1 00:12:34.568: BFD: [R1-to-R2] echo mode enabled, min-echo-rx-interval 50 ms *Mar 1 00:12:34.569: BFD: [R1-to-R2] starting echo timer, interval 50 ms *Mar 1 00:12:34.570: BFD: [R1-to-R2] sending async packet, state UP, interval 300 ms
What does this output indicate?
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
✓
BFD session is established and echo mode is active.
The debug output shows BFD session transitioning from DOWN to UP, with echo mode enabled and the async interval set to 300 ms. This indicates a successful BFD session establishment.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
BFD session is flapping between DOWN and UP states.
Why it's wrong here
The log shows a single DOWN to UP transition, indicating the session converged successfully rather than flapping repeatedly. It is tempting because DOWN and UP both appear in one line, but flapping requires multiple alternating transitions, which this output does not contain.
- ✓
BFD session is established and echo mode is active.
Why this is correct
The debug trace confirms the session transitioned from DOWN to UP in asynchronous mode, then negotiated echo mode with a 50 ms echo timer. Echo packets are looped back by the neighbour, so the stated establishment and active echo function match the logged events precisely.
- ✗
BFD session is down due to echo failure.
Why it's wrong here
The output shows echo mode enabled and the echo timer starting, with the session in UP state; no echo failure is reported. It is tempting because echo parameters appear, but echo failure would log missed echo packets and a transition to DOWN, neither of which is present.
- ✗
BFD async interval is misconfigured at 300 ms.
Why it's wrong here
The 300 ms async interval is the negotiated control-packet transmission rate, not a misconfiguration; the session reached UP and echo mode is active. It is tempting because a value differing from the 50 ms echo interval looks inconsistent, but async and echo intervals are independent timers serving different detection roles.
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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.