Question 496 of 1,000

Troubleshooting and Diagnostics →hardMultiple ChoiceObjective-mapped

Quick Answer

The answer is that the packet is dropped because no firewall policy matches the traffic. In FortiGate, even when a valid route exists in the routing table, every packet must be evaluated against firewall policies based on source, destination, service, and incoming interface; if no policy explicitly permits the traffic, the packet is silently dropped, as confirmed by a debug flow output showing messages like 'no matching policy' or 'deny by policy'. On the Fortinet NSE 7 Advanced Security NSE7 exam, this concept tests your ability to interpret debug flow output and distinguish between routing failures and policy-based drops—a common trap is assuming a valid route guarantees packet forwarding. Remember the memory tip: "Route gets you there, but policy lets you in."

NSE7 Troubleshooting and Diagnostics Practice Question

This NSE7 practice question tests your understanding of troubleshooting and diagnostics. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. 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.

Exhibit

Refer to the exhibit.

```
diagnose debug flow filter saddr 10.0.1.100
diagnose debug flow filter daddr 10.0.2.200
diagnose debug flow trace start 100
diagnose debug enable

# Output:
id=20085 trace_id=1 func=print_pkt_detail line=5757 msg="vd-root:0 received a packet from port1. src=10.0.1.100 dst=10.0.2.200 sport=12345 dport=80 proto=6"
id=20085 trace_id=1 func=resolve_ip_tuple line=3485 msg="tuple: 10.0.1.100->10.0.2.200, vd=0"
id=20085 trace_id=1 func=fw_pre_route_handler line=162 msg="no matching policy"
id=20085 trace_id=1 func=run_fw_handler line=59 msg="packet dropped"
```

Based on the debug flow output, what is the reason the packet is dropped?

Question 1hardmultiple choice

Full question →

Exhibit

Refer to the exhibit.

```
diagnose debug flow filter saddr 10.0.1.100
diagnose debug flow filter daddr 10.0.2.200
diagnose debug flow trace start 100
diagnose debug enable

# Output:
id=20085 trace_id=1 func=print_pkt_detail line=5757 msg="vd-root:0 received a packet from port1. src=10.0.1.100 dst=10.0.2.200 sport=12345 dport=80 proto=6"
id=20085 trace_id=1 func=resolve_ip_tuple line=3485 msg="tuple: 10.0.1.100->10.0.2.200, vd=0"
id=20085 trace_id=1 func=fw_pre_route_handler line=162 msg="no matching policy"
id=20085 trace_id=1 func=run_fw_handler line=59 msg="packet dropped"
```

A
The route to the destination is missing.
Why wrong: No routing-related messages appear in the output.
B
There is no firewall policy that matches the traffic.
The message 'no matching policy' clearly states this.
C
The packet has an invalid source IP address.
Why wrong: The debug shows no validation issue with the source IP.
D
The session table is full.
Why wrong: Session table full would show a different error.

Full breakdown with real-world context →

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

✓

There is no firewall policy that matches the traffic.

The debug flow output indicates that the packet was dropped because no firewall policy matched the traffic. In FortiGate, even if a valid route exists, the packet must be evaluated against firewall policies; if no policy permits the traffic based on source, destination, service, and interface, the packet is silently dropped. The debug flow will show a message like 'no matching policy' or 'deny by policy' in such cases.

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 route to the destination is missing.
Why it's wrong here
No routing-related messages appear in the output.
✓
There is no firewall policy that matches the traffic.
Why this is correct
The message 'no matching policy' clearly states this.
Related concept
Read the scenario before looking for a memorised answer.
✗
The packet has an invalid source IP address.
Why it's wrong here
The debug shows no validation issue with the source IP.
✗
The session table is full.
Why it's wrong here
Session table full would show a different error.

Common exam traps

Common exam trap: answer the scenario, not the keyword

The trap here is that candidates often assume a packet drop is due to a missing route when the debug flow shows a policy drop, because they overlook that FortiGate processes routing before policies and the debug flow output explicitly indicates the stage where the drop occurred.

Trap categories for this question

Command / output trap
No routing-related messages appear in the output.

Detailed technical explanation

How to think about this question

FortiGate's packet processing follows a strict order: first route lookup, then firewall policy lookup, then session creation. The debug flow output shows the packet reached the policy lookup stage but was dropped there, confirming that a route existed (otherwise it would have been dropped earlier). In real-world scenarios, this often happens when a new subnet is added but the corresponding firewall policy is not created, or when traffic arrives on an unexpected interface that lacks a matching policy.

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 small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.

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.

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FAQ

Questions learners often ask

What does this NSE7 question test?

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: There is no firewall policy that matches the traffic. — The debug flow output indicates that the packet was dropped because no firewall policy matched the traffic. In FortiGate, even if a valid route exists, the packet must be evaluated against firewall policies; if no policy permits the traffic based on source, destination, service, and interface, the packet is silently dropped. The debug flow will show a message like 'no matching policy' or 'deny by policy' in such cases.

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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Last reviewed: Jun 11, 2026

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