NSE4 High Availability and Diagnostics Practice Question
A company has two remote sites connected via an SD-WAN overlay. The headquarters uses a FortiGate with two WAN links: Fiber (priority 1) and LTE (priority 2). The SD-WAN rule for business-critical traffic uses the 'best quality' strategy with SLA targets for latency and jitter. The fiber link occasionally experiences high jitter but low latency. The engineer notices that traffic is not failing over to LTE even when jitter exceeds the threshold. What is the most likely reason?
⚠ Common exam trap
Many candidates assume jitter is automatically monitored in SD-WAN SLA, but FortiGate requires explicit configuration of each metric (latency, jitter, packet loss) in the performance SLA; otherwise, unconfigured metrics are ignored for failover decisions.
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 performance SLA for jitter is not configured, only latency.
The SD-WAN rule uses the 'best quality' strategy, which selects the best link based on configured SLA metrics. If only latency is configured in the performance SLA, jitter exceeding the threshold will not trigger a failover, as the SLA only evaluates the configured metrics. The fiber link may still meet the latency SLA, so traffic remains on it despite high jitter.
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 performance SLA for jitter is not configured, only latency.
Why this is correct
Correct; only configured SLA targets are measured for failover.
- ✗
The SD-WAN rule has SLA match set to 'either' instead of 'all'.
Why it's wrong here
Incorrect; 'either' would trigger failover if any SLA target fails.
- ✗
The LTE link has a higher cost and is not considered for failover.
Why it's wrong here
Incorrect; cost affects route selection, not failover trigger.
- ✗
The fiber link has a higher interface weight.
Why it's wrong here
Incorrect; weight does not affect SLA failover.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This NSE4 practice question is part of Courseiva's free Fortinet 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 NSE4 exam.