NSE7 Advanced Networking and SD-WAN Practice Question
An administrator configures SD-WAN with two members (wan1, wan2) and a performance SLA for ICMP to 1.1.1.1. The SD-WAN rule is set to 'Best Quality' with 'latency' metric. The admin notices that traffic sometimes switches to the other link even when the current link has acceptable latency. Which action can reduce unnecessary flapping?
⚠ Common exam trap
Test-takers frequently confuse 'hysteresis' with 'increasing the probe interval' (Option B), thinking that less frequent measurements will reduce flapping, but hysteresis is the correct mechanism because it introduces a deadband to prevent switching on minor fluctuations, whereas a longer interval only delays detection and does not prevent the oscillation.
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
✓
Configure a hysteresis value for the SLA
Configuring a hysteresis value for the SLA introduces a buffer or deadband around the latency threshold. This prevents the SD-WAN from switching links when latency fluctuates slightly above and below the threshold, which is the root cause of flapping. Without hysteresis, even a minor transient spike in latency can trigger a switch, even if the link's overall performance is acceptable.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Configure a hysteresis value for the SLA
Why this is correct
Hysteresis adds a buffer: the link must be significantly better before switching, reducing flapping.
- ✗
Increase the SLA probe interval
Why it's wrong here
Increasing interval would make detection slower but not prevent flapping due to minor fluctuations.
- ✗
Use 'manual' strategy instead
Why it's wrong here
Manual strategy would not automatically switch, but it defeats the purpose.
- ✗
Increase the 'update-cascade-interface' setting
Why it's wrong here
This setting is for updating routes, not for flapping prevention.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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