NSE7 Advanced Networking and SD-WAN Practice Question
A FortiGate with two WAN interfaces configured in an SD-WAN setup uses the 'lowest-cost' load balancing algorithm. The performance SLA monitors latency and jitter. If wan1 has a cost of 10 and wan2 has a cost of 20, but wan1 is experiencing 50% packet loss, what will happen to traffic?
⚠ Common exam trap
Watch out — candidates often assume the 'lowest-cost' algorithm always uses the link with the lowest cost regardless of link health, but FortiGate SD-WAN first checks the SLA status and only considers active (alive) members for the cost comparison.
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
✓
Traffic is sent to wan2 because wan1 is considered dead
When an SD-WAN member interface fails the performance SLA (e.g., 50% packet loss), FortiGate marks it as 'dead' and removes it from the active member set. The 'lowest-cost' algorithm then selects the next lowest-cost member that is alive, which is wan2 (cost 20). Traffic is not load-balanced equally because wan1 is dead, and it is not dropped because wan2 is available.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Traffic is distributed equally between both links
Why it's wrong here
Lowest-cost does not distribute equally; it selects the best path.
- ✗
Traffic is dropped until wan1 recovers
Why it's wrong here
Traffic will be sent to the next available member.
- ✗
Traffic continues using wan1 because cost is lower
Why it's wrong here
If wan1 fails SLA, it is marked dead and not used.
- ✓
Traffic is sent to wan2 because wan1 is considered dead
Why this is correct
wan1 fails SLA so it's dead, traffic uses wan2.
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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.