NSE7 Advanced Networking and SD-WAN Practice Question
A FortiGate is configured with two SD-WAN members: port1 (WAN1) and port2 (WAN2). An SD-WAN rule routes traffic from the internal subnet 10.0.1.0/24 to the internet using the 'volume' load-balancing algorithm. The rule is configured with a volume ratio of 70:30 for port1:port2. After some time, the administrator notices that port1 is handling approximately 90% of the traffic volume, while port2 handles only 10%. What is the most likely cause of this imbalance?
⚠ Common exam trap
The trap here is assuming that the volume algorithm dynamically moves existing sessions to maintain the ratio, when it only affects new sessions.
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 volume algorithm may not achieve the exact ratio if there are long-lived sessions that are not re-evaluated; existing sessions remain on their original member, causing an imbalance over time.
The volume algorithm aims to distribute traffic volume according to the configured ratio, but it does not rebalance existing sessions. Long-lived sessions can cause a persistent imbalance because they remain on their original member. The algorithm only affects new session assignments, so if a few large flows are pinned to one member, the overall volume can deviate from the target ratio.
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 volume algorithm uses the configured volume ratio only when both members are alive and meet the SLA; if port2 is dead, all traffic goes to port1.
Why it's wrong here
If port2 were dead, all traffic would indeed go to port1, resulting in a 100:0 split, not 90:10. The scenario shows some traffic on port2, so it is likely alive. The volume algorithm does consider SLA status, but the imbalance is not due to port2 being dead because some traffic is still being routed through it.
- ✗
The volume algorithm distributes traffic based on the configured ratio, but the ratio is applied to the number of sessions, not the volume of data.
Why it's wrong here
The volume algorithm is specifically designed to distribute traffic based on data volume, not session count. It measures the bytes sent and received on each member and adjusts the distribution to match the configured ratio. If it were based on sessions, the algorithm would be called 'session count' or similar. The observed imbalance suggests a different issue.
- ✗
The volume algorithm uses the configured ratio only as a target, but it also considers the current bandwidth usage; if port1 has higher bandwidth, it may receive more traffic.
Why it's wrong here
The volume algorithm does not consider current bandwidth usage as a primary factor; it aims to distribute volume according to the configured ratio. The algorithm tracks the cumulative volume on each member and adjusts new session assignments to achieve the desired ratio. If port1 is receiving more traffic, it is likely due to a configuration or operational issue, not because of higher bandwidth.
- ✓
The volume algorithm may not achieve the exact ratio if there are long-lived sessions that are not re-evaluated; existing sessions remain on their original member, causing an imbalance over time.
Why this is correct
The volume algorithm distributes new sessions based on the current volume ratio, but existing sessions are not rebalanced. If many long-lived sessions (e.g., large downloads) are established on port1, they continue to use port1, skewing the overall volume. New sessions may be assigned to port2 to compensate, but if the long-lived sessions dominate, the ratio can deviate significantly from the configured target.
Visual reference
Go deeper
Related to this question
About these practice questions
One of 718 original NSE7 practice questions on Courseiva, each with a full explanation and wrong-answer analysis — not exam dumps or protected exam content. Learn why practice questions differ from exam dumps →
JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Fortinet exam blueprint
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.