NSE7 Troubleshooting and Diagnostics Practice Question
A FortiGate is configured with SD-WAN and multiple members. The administrator notices that traffic to a critical application is consistently routed over a low-quality link, even though a better link is available. The SD-WAN rule uses the 'Best Quality' strategy with a performance SLA. What is the most likely reason?
⚠ Common exam trap
It's easy for candidates to assume 'Best Quality' always picks the link with the highest bandwidth or lowest cost, when in fact it strictly selects based on SLA compliance, not raw capacity or administrative preference.
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 better link is failing its SLA probes
When an SD-WAN rule uses the 'Best Quality' strategy with a performance SLA, the FortiGate selects the member link that best meets the SLA targets (e.g., jitter, latency, packet loss). If the better link is failing its SLA probes, it is considered out of compliance and will not be selected, even if it is physically available and has higher bandwidth. This causes traffic to be routed over the lower-quality link that still passes the SLA.
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 better link is failing its SLA probes
Why this is correct
Under Best Quality, SD-WAN selects members by measured SLA performance. If the superior link fails its performance SLA probes, it is marked out of SLA and excluded, so traffic falls back to the remaining member despite that link's better raw capacity.
- ✗
The better link is in 'standby' mode
Why it's wrong here
A standby member is excluded from Best Quality selection until all active members breach the SLA, so the better link is never chosen while any active member remains within threshold. It is tempting because standby is a real SD-WAN configuration, and would be correct if the design required a backup path only.
- ✗
The SD-WAN rule is using source-based routing
Why it's wrong here
Source-based routing selects a member by source address rather than by measured SLA performance, so the Best Quality strategy is bypassed entirely. It is tempting because source-based rules are a legitimate SD-WAN design for steering specific subnets, and would be correct if the requirement were deterministic per-subnet path selection.
- ✗
The application traffic is not matching the SD-WAN rule
Why it's wrong here
If traffic never matches the SD-WAN rule, the Best Quality strategy and its performance SLA are never evaluated, so the session follows the default route instead. It is tempting because rule-matching failures genuinely cause unexpected path selection, but here the rule is stated as applying to the critical application.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This NSE7 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 NSE7 exam.