NSE7 Advanced Networking and SD-WAN Practice Question
You are troubleshooting BFD on a FortiGate SD-WAN deployment. BFD is configured on two WAN interfaces (wan1, wan2) with a minimum transmit interval of 100 ms and a multiplier of 3. The network experiences occasional jitter causing packet loss. After a brief outage, the BFD session does not recover. Which setting should be adjusted to improve BFD resilience without significantly increasing failover time?
⚠ Common exam trap
The trap here is that candidates mistakenly increase the transmit interval (Option C) thinking it reduces jitter sensitivity, but that actually increases failover time for all failures, whereas adjusting the multiplier provides resilience against intermittent loss without proportionally increasing detection time for sustained outages.
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
✓
Increase the BFD multiplier to 4 or higher.
Increasing the BFD multiplier (from 3 to 4 or higher) allows the session to tolerate more lost BFD control packets before declaring a failure. This directly addresses the jitter-induced packet loss without changing the detection timing for sustained outages, as the multiplier only affects the number of missed packets required to trigger a failure. The minimum transmit interval remains at 100 ms, so the base detection time (multiplier × interval) increases only slightly, preserving fast failover for true link failures.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Disable BFD and rely on route timers.
Why it's wrong here
Disabling BFD would increase failover time.
- ✗
Enable BFD on the management interface.
Why it's wrong here
BFD on management does not affect SD-WAN link detection.
- ✗
Increase the BFD minimum transmit interval on both interfaces.
Why it's wrong here
Increasing the interval would slow down detection, not improve resilience to jitter.
- ✓
Increase the BFD multiplier to 4 or higher.
Why this is correct
A higher multiplier allows more missed packets, making BFD more tolerant to transient jitter.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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