NSE7 Troubleshooting and Diagnostics Practice Question
An administrator runs 'diagnose debug application fnbam -1' and sees messages like 'LB_SELECT: selected server 10.0.0.2:80' but the client connection fails. The FortiGate is configured with server load balancing. What could be the issue?
⚠ Common exam trap
The trap here is that candidates see 'LB_SELECT' and assume the load-balancing decision is the problem, when in fact the debug output confirms the selection logic is working, and the failure lies in the server's reachability or health.
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 real server is not reachable or is down
The 'LB_SELECT: selected server 10.0.0.2:80' message indicates that the FortiGate's load-balancing process has chosen a real server for the connection. However, the client connection fails, which points to a problem with the selected server itself. The most common cause is that the real server is unreachable or down, preventing the TCP handshake or HTTP response from completing, even though the load-balancing decision was made successfully.
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 real server is not reachable or is down
Why this is correct
Correct. The debug shows selection, but the server may not be listening or reachable.
- ✗
The load balancing algorithm is set to least-connection
Why it's wrong here
The algorithm selection is shown; it does not cause failure.
- ✗
The persistence setting is misconfigured
Why it's wrong here
Persistence affects which server is chosen, not connection success.
- ✗
The virtual server IP is overlapping with a physical interface
Why it's wrong here
Overlap would cause address conflict, not server selection failure.
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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.