The answer is that the 'best quality' strategy uses bandwidth as a tiebreaker when the performance SLA is met. In FortiOS 7.2, when multiple WAN links satisfy the configured latency and jitter thresholds, the FortiGate SD-WAN rule does not continue comparing those metrics; instead, it selects the link with the highest bandwidth. This explains why the VoIP traffic uses WAN2 (100 Mbps) over WAN1 (50 Mbps), even though WAN1 has lower latency—both links passed the SLA, so bandwidth became the deciding factor. On the Fortinet NSE 4 Network Security Professional NSE4 exam, this scenario tests your understanding of the SD-WAN best quality tiebreaker hierarchy: SLA metrics first, then bandwidth. A common trap is assuming the best quality strategy always picks the lowest latency link, but it only does so when SLA thresholds are not met. Memory tip: "SLA first, then size wins"—if both links meet the SLA, the fattest pipe gets the traffic.
NSE4 System and Network Administration Practice Question
This NSE4 practice question tests your understanding of system and network administration. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A company has a FortiGate 200F with FortiOS 7.2 and two ISPs (WAN1: 100 Mbps, WAN2: 50 Mbps). The company uses SD-WAN to load balance outbound internet traffic. Recently, the company added a new VoIP application that requires low latency and jitter. The administrator configured an SD-WAN rule to match the VoIP traffic and set the strategy to 'best quality' with a performance SLA measuring latency and jitter. However, after testing, the VoIP traffic is still using WAN2 (the slower link) even when WAN1 has lower latency. The performance SLA shows both links meeting the SLA thresholds. What is the most likely reason?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The 'best quality' strategy uses bandwidth as a tiebreaker when SLA is met.
When the 'best quality' strategy is used in an SD-WAN rule, FortiGate selects the best-performing link based on the configured performance SLA metrics (e.g., latency and jitter). However, if multiple links meet the SLA thresholds, the tiebreaker is the link with the highest bandwidth. In this scenario, both WAN1 and WAN2 meet the SLA, so FortiGate selects WAN2 because it has higher bandwidth (100 Mbps vs. 50 Mbps), not because of latency. This explains why VoIP traffic uses WAN2 despite WAN1 having lower latency.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 'best quality' strategy uses bandwidth as a tiebreaker when SLA is met.
Why this is correct
Fortinet's best quality uses bandwidth to break ties.
Clue confirmation
The clue words "best", "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The VoIP traffic is being offloaded by NPU bypassing SD-WAN.
Why it's wrong here
NPU offloading does not bypass SD-WAN rules.
✗
The administrator needs to enable 'set internet-service enable' on the rule.
Why it's wrong here
Internet service is for specific applications, not required.
✗
The SD-WAN rule is not matching the VoIP traffic correctly.
Why it's wrong here
The administrator tested and confirmed the rule is applied.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume 'best quality' always selects the link with the best SLA metrics (e.g., lowest latency), but FortiGate uses bandwidth as a tiebreaker when multiple links meet the SLA, which is a subtle but critical detail tested in NSE4.
Detailed technical explanation
How to think about this question
The 'best quality' strategy in FortiOS SD-WAN uses a weighted metric system where SLA compliance is checked first. If multiple links satisfy the SLA, FortiGate applies a tiebreaker based on the link's bandwidth (higher bandwidth wins) by default, unless 'set load-balance-mode' is configured differently. This behavior is defined in the FortiOS SD-WAN documentation under 'best quality' strategy logic. In real-world deployments, administrators often overlook this tiebreaker and assume 'best quality' always picks the lowest latency link, leading to unexpected traffic distribution.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the NSE4 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
System and Network Administration — This question tests System and Network Administration — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The 'best quality' strategy uses bandwidth as a tiebreaker when SLA is met. — When the 'best quality' strategy is used in an SD-WAN rule, FortiGate selects the best-performing link based on the configured performance SLA metrics (e.g., latency and jitter). However, if multiple links meet the SLA thresholds, the tiebreaker is the link with the highest bandwidth. In this scenario, both WAN1 and WAN2 meet the SLA, so FortiGate selects WAN2 because it has higher bandwidth (100 Mbps vs. 50 Mbps), not because of latency. This explains why VoIP traffic uses WAN2 despite WAN1 having lower latency.
What should I do if I get this NSE4 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "best", "most likely". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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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.
Question Discussion
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