The correct answer is to run both diagnose sniffer packet and diagnose debug flow. The sniffer command with the filter 'any host 10.1.2.100 4' captures all packets to and from the target server at the interface level, which is essential for diagnosing packet drop on VLAN because it reveals whether traffic from VLAN 100 is physically arriving at the FortiGate or being silently discarded due to a Layer 2 VLAN misconfiguration. The debug flow command then traces the packet’s path through the firewall’s processing pipeline, showing exactly where a security policy, routing lookup, or session table entry causes the blockage. On the Fortinet NSE 7 Advanced Security NSE7 exam, this pairing tests your ability to isolate whether a drop occurs before or after policy evaluation—a common trap is relying solely on the sniffer and missing internal drops, or using debug flow without confirming the packet even reaches the interface. Remember the memory tip: sniff the wire to see it arrive, then flow to see it die.
NSE7 Troubleshooting and Diagnostics Practice Question
This NSE7 practice question tests your understanding of troubleshooting and diagnostics. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
An administrator is troubleshooting a scenario where traffic from VLAN 100 to a server at 10.1.2.100 is being blocked. The FortiGate has an active security policy allowing the traffic and the routing table shows a correct route. Which TWO diagnostic commands should the administrator run to identify the cause of the blockage?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
diagnose sniffer packet any 'host 10.1.2.100' 4
Option A is correct because 'diagnose sniffer packet any host 10.1.2.100 4' captures packets to/from the server at the interface level, allowing the administrator to see if traffic from VLAN 100 is actually arriving at the FortiGate and whether it is being dropped or forwarded. This command helps identify if the issue is at Layer 2 (e.g., VLAN misconfiguration) or Layer 3 (e.g., routing or firewall drops).
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.
✓
diagnose sniffer packet any 'host 10.1.2.100' 4
Why this is correct
Captures packets to verify traffic reaches the FortiGate.
Related concept
Read the scenario before looking for a memorised answer.
✗
get system performance status
Why it's wrong here
Shows overall system performance, not specific traffic blocking.
Shows active sessions, but not helpful for blocked traffic that never creates a session.
✓
diagnose debug flow
Why this is correct
Provides detailed flow trace showing policy matching and any blocks.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often choose 'diagnose sys session list' thinking it shows blocked traffic, but it only lists established sessions, not dropped packets or failed session creation attempts.
Trap categories for this question
Command / output trap
Shows overall system performance, not specific traffic blocking.
Detailed technical explanation
How to think about this question
The 'diagnose debug flow' command (Option E) enables flow-based debugging that traces the packet's path through the FortiGate's firewall, routing, and policy engine, logging each decision (e.g., policy match, NAT, drop reason). In contrast, 'diagnose sniffer packet' captures raw packets at the kernel level, useful for verifying ingress/egress and VLAN tagging. Together, these two commands cover both the packet-level and flow-level perspectives, which is critical when a policy exists but traffic is still blocked due to issues like asymmetric routing, session helper interference, or implicit deny rules.
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 help-desk technician troubleshoots why a newly connected PC cannot reach shared printers on the same floor. The cable is good, the switch port is active, but the PC is in VLAN 20 and the printers are in VLAN 10. The uplink trunk only allows VLAN 10. A trunk being up does not mean every VLAN crosses it.
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.
Troubleshooting and Diagnostics — This question tests Troubleshooting and Diagnostics — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: diagnose sniffer packet any 'host 10.1.2.100' 4 — Option A is correct because 'diagnose sniffer packet any host 10.1.2.100 4' captures packets to/from the server at the interface level, allowing the administrator to see if traffic from VLAN 100 is actually arriving at the FortiGate and whether it is being dropped or forwarded. This command helps identify if the issue is at Layer 2 (e.g., VLAN misconfiguration) or Layer 3 (e.g., routing or firewall drops).
What should I do if I get this NSE7 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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