- A
The destination NAT on the allow policy is misconfigured
Why wrong: NAT configuration on the allow policy would not prevent the policy from being evaluated; the issue is policy matching order.
- B
The FortiGate's DNS server is not resolving the FQDN correctly
Why wrong: If DNS resolution were the issue, the FQDN object would not contain the IP at all, and the policy would not match.
- C
The antivirus profile on the allow policy is blocking the website
Why wrong: Antivirus blocking would occur after the policy match; since the traffic is not reaching the allow policy, it cannot be blocked by its profiles.
- D
The FQDN object resolved to the IP after the policy was created, but the policy lookup uses the cached IP and matches before the allow policy
Policy lookup matches the first policy where source/destination conditions are met. Since the FQDN object resolved to the destination IP, a higher-priority policy matches and the intended allow policy is never evaluated.
Quick Answer
The most likely cause is that the FQDN object in a higher-priority policy resolved to the IP 203.0.113.5 after the policy was created, and the FortiGate’s policy lookup uses the cached IP, matching the deny or different-NAT rule before the intended allow policy. This occurs because FortiGate processes firewall policies sequentially from top to bottom; when an FQDN-based policy is placed above the allow rule, its cached IP address can inadvertently match traffic that should be permitted, effectively blocking or misrouting it. On the Fortinet NSE 4 Network Security Professional exam, this scenario tests your understanding of FQDN policy order troubleshooting and the critical distinction between static IP objects and dynamic FQDN resolution—a common trap where admins assume FQDN policies update instantly without considering policy sequence. Remember: FQDN resolution is cached, so policy order still rules; always place specific FQDN allow rules above broader deny rules, or use a dedicated address object to avoid surprises. A useful memory tip is “Cache before cachet”—the cached IP takes precedence over the policy’s intended effect.
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 has configured a firewall policy allowing traffic from the internal network (10.0.1.0/24) to the internet (any). Users report that they cannot access a specific website (203.0.113.5). The admin runs 'diagnose firewall fqdn list' and sees that the FQDN object used in a policy above the allow policy resolves to an IP that includes 203.0.113.5. What is the MOST likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"most likely"Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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 FQDN object resolved to the IP after the policy was created, but the policy lookup uses the cached IP and matches before the allow policy
Firewall policies are matched from top to bottom. If a higher-priority policy (with a lower policy ID) matches the traffic and denies or applies different NAT, it will be processed before the intended allow policy. In this case, an FQDN-based policy above the allow policy matches the destination IP, causing the traffic to be handled by that policy instead.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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 destination NAT on the allow policy is misconfigured
Why it's wrong here
NAT configuration on the allow policy would not prevent the policy from being evaluated; the issue is policy matching order.
- ✗
The FortiGate's DNS server is not resolving the FQDN correctly
Why it's wrong here
If DNS resolution were the issue, the FQDN object would not contain the IP at all, and the policy would not match.
- ✗
The antivirus profile on the allow policy is blocking the website
Why it's wrong here
Antivirus blocking would occur after the policy match; since the traffic is not reaching the allow policy, it cannot be blocked by its profiles.
- ✓
The FQDN object resolved to the IP after the policy was created, but the policy lookup uses the cached IP and matches before the allow policy
Why this is correct
Policy lookup matches the first policy where source/destination conditions are met. Since the FQDN object resolved to the destination IP, a higher-priority policy matches and the intended allow policy is never evaluated.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
- Static NAT maps one inside address to one outside address.
- PAT allows many inside hosts to share one public address using ports.
- Inside local and inside global describe the private and translated addresses.
- NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
- Identify inside and outside interfaces first.
- Check whether the scenario needs static NAT, dynamic NAT or PAT.
- Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related NSE4 NAT questions on configuration and troubleshooting.
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Firewall Policies and NAT — study guide chapter
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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 — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: The FQDN object resolved to the IP after the policy was created, but the policy lookup uses the cached IP and matches before the allow policy — Firewall policies are matched from top to bottom. If a higher-priority policy (with a lower policy ID) matches the traffic and denies or applies different NAT, it will be processed before the intended allow policy. In this case, an FQDN-based policy above the allow policy matches the destination IP, causing the traffic to be handled by that policy instead.
What should I do if I get this NSE4 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related NSE4 NAT questions on configuration and troubleshooting.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Same concept, more angles
1 more ways this is tested on NSE4
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. An admin notices that a firewall policy allowing inbound HTTPS to a server is not matching traffic. The policy has source set to 'all', destination to the server's IP, and service to HTTPS. The admin checks the policy list and sees that policy ID 1 matches the traffic. What is the MOST likely reason the intended policy (ID 10) is not matching?
hard- ✓ A.Policy ID 1 has a higher priority and matches before policy ID 10
- B.The firewall policy is disabled
- C.The service object for HTTPS is misconfigured in policy ID 10
- D.The destination address is incorrect in policy ID 10
Why A: Policy ID 1 has a higher priority because FortiGate evaluates firewall policies in sequential order from top to bottom. When policy ID 1 matches the traffic (e.g., it also allows HTTPS to the same destination), the traffic is processed by policy ID 1 and never reaches policy ID 10. This is the most likely reason the intended policy is not matching.
Last reviewed: Jun 21, 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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