- A
Reboot the FortiGate to clear any session table issues
Why wrong: Rebooting is not a diagnostic step; it may clear symptoms but not identify root cause.
- B
Examine the IP Pool configuration for correct interface binding or port exhaustion
Misconfigured pool (e.g., wrong interface) or port exhaustion can cause NAT failure.
- C
Verify that the firewall policy is being hit using 'diagnose firewall fwpolicy list' or logs
If the policy is not hit, NAT will not be applied.
- D
Check the session table using 'diagnose sys session list' to see if NAT is applied
The session table shows the translated source IP, confirming if NAT is working.
- E
Disable all other firewall policies to isolate the issue
Why wrong: This is a drastic step and not recommended for initial diagnosis.
NSE4 Firewall Policies and NAT Practice Question
This NSE4 practice question tests your understanding of firewall policies and nat. 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.
A FortiGate admin is troubleshooting an issue where traffic from VLAN 10 to the internet is not being NATed even though a policy-based NAT rule is configured. The admin verifies that the firewall policy uses the correct IP Pool. Which THREE steps should the admin take to diagnose the problem? (Choose three.)
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
Examine the IP Pool configuration for correct interface binding or port exhaustion
Option B is correct because policy-based NAT requires the IP Pool to be bound to the correct outgoing interface (the one the traffic egresses on). If the interface binding is wrong or the pool has exhausted its port range (e.g., all PAT ports are used), NAT will fail silently. Examining the IP Pool configuration directly reveals these misconfigurations.
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.
- ✗
Reboot the FortiGate to clear any session table issues
Why it's wrong here
Rebooting is not a diagnostic step; it may clear symptoms but not identify root cause.
- ✓
Examine the IP Pool configuration for correct interface binding or port exhaustion
Why this is correct
Misconfigured pool (e.g., wrong interface) or port exhaustion can cause NAT failure.
Related concept
Read the scenario before looking for a memorised answer.
- ✓
Verify that the firewall policy is being hit using 'diagnose firewall fwpolicy list' or logs
Why this is correct
If the policy is not hit, NAT will not be applied.
Related concept
Read the scenario before looking for a memorised answer.
- ✓
Check the session table using 'diagnose sys session list' to see if NAT is applied
Why this is correct
The session table shows the translated source IP, confirming if NAT is working.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Disable all other firewall policies to isolate the issue
Why it's wrong here
This is a drastic step and not recommended for initial diagnosis.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume a firewall policy with NAT enabled will always work, overlooking that the IP Pool itself must be correctly bound to the egress interface and not exhausted, and that rebooting or disabling policies are not valid diagnostic steps.
Detailed technical explanation
How to think about this question
Policy-based NAT on FortiGate uses an IP Pool object that must be explicitly referenced in the firewall policy's 'NAT' column. The IP Pool's 'Interface' field must match the egress interface of the traffic; if it is set to 'any' or a different interface, NAT may not apply. Additionally, for PAT pools, the FortiGate tracks source port usage per destination IP; if all ports in the pool are exhausted (e.g., due to many concurrent sessions), new sessions will fail NAT and be dropped or sent without translation.
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.
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FAQ
Questions learners often ask
What does this NSE4 question test?
Firewall Policies and NAT — This question tests Firewall Policies and NAT — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Examine the IP Pool configuration for correct interface binding or port exhaustion — Option B is correct because policy-based NAT requires the IP Pool to be bound to the correct outgoing interface (the one the traffic egresses on). If the interface binding is wrong or the pool has exhausted its port range (e.g., all PAT ports are used), NAT will fail silently. Examining the IP Pool configuration directly reveals these misconfigurations.
What should I do if I get this NSE4 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.
About these practice questions
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Last reviewed: Jun 24, 2026
This NSE4 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 NSE4 exam.
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