hardMultiple ChoiceObjective-mapped
300-410 Practice Question: Runs the following command on Router R1: R1# show…
A network engineer runs the following command on Router R1:
R1# show bfd neighbors detail
IPv4 Sessions NeighborAddr LD/RD Int State Holdown(mult) Intf
10.1.1.2 1/3 Gi0/0 Down 0(0) Gi0/0
Session state is DOWN OurAddr: 10.1.1.1 Handle: 1 Local Diag: 1, Demand mode: 0, Poll bit: 0 MinTxInt: 1000000, MinRxInt: 1000000, Multiplier: 3 Received MinRxInt: 1000000, Received Multiplier: 3 Holddown (hits): 0(0) Rx Count: 0, Tx Count: 50
Based on this output, what is the most likely cause of the BFD session being down?
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 BFD session is down because the neighbor is not responding to BFD packets, likely due to a network connectivity issue or neighbor misconfiguration.
The Local Diag field shows 1, which indicates 'Control Detection Time Expired'. This means the local router did not receive BFD control packets from the neighbor within the expected time. The Rx Count is 0, confirming no packets were received. Tx Count is 50, so the local router is sending packets but not receiving any.
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 neighbor router is not configured for BFD.
Why it's wrong here
While possible, the diagnostic code 1 specifically indicates that the control detection time expired, meaning packets were not received. This could be due to a connectivity issue or neighbor not sending.
- ✗
The BFD session is down because the local router is not sending BFD packets.
Why it's wrong here
Tx Count is 50, so packets are being sent.
- ✓
The BFD session is down because the neighbor is not responding to BFD packets, likely due to a network connectivity issue or neighbor misconfiguration.
Why this is correct
Local Diag 1 means control detection time expired, and Rx Count is 0, indicating no packets received from the neighbor. This points to a problem with the neighbor or the path.
- ✗
The BFD session is down because the multiplier is set too low.
Why it's wrong here
The multiplier is 3, which is standard. The diagnostic code indicates a timeout, not a configuration issue.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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