NSE7 Troubleshooting and Diagnostics Practice Question
A FortiGate administrator notices that traffic from a specific subnet is being dropped unexpectedly. The security policy allows the traffic, and there are no firewall policies blocking it. What is the most efficient first step to identify the cause of the drops?
⚠ Common exam trap
The trap here is that candidates often jump to 'diagnose debug flow' as the default troubleshooting tool, but it only works after a session is created, missing pre-session drops that the sniffer can immediately expose.
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
✓
Use the 'diag sniffer packet any "host 10.0.1.0/24" 4' command to capture packets and analyze where they are dropped.
The 'diag sniffer packet any "host 10.0.1.0/24" 4' command captures packets at the kernel level before firewall processing, allowing you to see if traffic is reaching the FortiGate and where it is being dropped (e.g., due to reverse-path forwarding, session helper, or DoS policies). This is the most efficient first step because it provides immediate, low-level visibility into packet drops without requiring configuration changes or waiting for logs.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Use the 'diag sniffer packet any "host 10.0.1.0/24" 4' command to capture packets and analyze where they are dropped.
Why this is correct
Packet sniffer with filter can capture the actual packets and show the drop reason in the output.
- ✗
Run 'diagnose debug flow' with the source IP and look for 'no matching policy' or 'dropped' messages.
Why it's wrong here
Debug flow is useful but may not show drops that occur before policy matching, such as route issues.
- ✗
Enable 'deny-log' on all policies and check logs for the subnet.
Why it's wrong here
If traffic is not matched by any policy, deny-log won't capture it.
- ✗
Enable global traffic logging and review logs after some traffic passes.
Why it's wrong here
Global logging may generate excessive logs and not pinpoint the issue quickly.
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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.