- A
NAT is disabled, so the server cannot send replies back.
Why wrong: NAT is not required for internal traffic; the server can reply directly to the source IP.
- B
The policy order is incorrect; a deny policy above is blocking traffic.
Why wrong: The administrator checked for overlapping policies and found none; if there were a deny policy above, it would block all traffic from VLAN10 to VLAN20, not just HTTPS.
- C
A security profile applied to the policy is blocking the HTTPS traffic.
Security profiles such as SSL inspection or application control can block or interfere with HTTPS traffic, especially if the server certificate is not trusted.
- D
The schedule is configured incorrectly and the policy is inactive during the current time.
Why wrong: The schedule is set to Always, so the policy is always active.
Quick Answer
The answer is that a security profile applied to the policy is blocking the HTTPS traffic. Even when a firewall policy explicitly allows HTTPS on port 443, security profiles—such as web filtering, application control, or SSL inspection—can inspect and deny the traffic at a deeper layer, overriding the basic permit rule. On the Fortinet NSE 4 Network Security Professional exam, this scenario tests your understanding of how security profiles interact with firewall policies; a common trap is assuming that a permit action alone guarantees traffic flow, ignoring that profiles can silently drop packets. Remember that in FortiGate, the policy’s “Allow” action only opens the door, but security profiles act as the bouncers inside—if they block HTTPS, the traffic never reaches the server. Memory tip: “Permit the port, but profile the content—if HTTPS fails, check the inspection.”
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 company uses FortiGate with firewall policies to control access between internal VLANs. Users in VLAN 10 report they can access internet but cannot reach a server in VLAN 20 on port 443. The server is reachable from other VLANs. The administrator checks the firewall policy configuration: there is a policy from VLAN10 to VLAN20 allowing HTTPS, with NAT disabled and logging enabled. The policy has a schedule set to 'Always'. The administrator also checks that there are no overlapping policies. 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.
Clue:
"always"Why it matters: Absolute qualifier. An answer using 'always' is only correct if there are genuinely no exceptions — absolute statements are often wrong in networking.
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
A security profile applied to the policy is blocking the HTTPS traffic.
The correct answer is C because security profiles (such as web filtering, application control, or SSL inspection) applied to a firewall policy can inspect and block HTTPS traffic even when the policy itself allows the service. Since the server is reachable from other VLANs and the policy explicitly permits HTTPS with NAT disabled and logging enabled, the most likely cause is that a security profile is dropping or denying the traffic.
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.
- ✗
NAT is disabled, so the server cannot send replies back.
Why it's wrong here
NAT is not required for internal traffic; the server can reply directly to the source IP.
- ✗
The policy order is incorrect; a deny policy above is blocking traffic.
Why it's wrong here
The administrator checked for overlapping policies and found none; if there were a deny policy above, it would block all traffic from VLAN10 to VLAN20, not just HTTPS.
- ✓
A security profile applied to the policy is blocking the HTTPS traffic.
Why this is correct
Security profiles such as SSL inspection or application control can block or interfere with HTTPS traffic, especially if the server certificate is not trusted.
Clue confirmation
The clue words "most likely", "always" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
The schedule is configured incorrectly and the policy is inactive during the current time.
Why it's wrong here
The schedule is set to Always, so the policy is always active.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume a policy allowing a service with NAT disabled is sufficient for reachability, overlooking that security profiles can independently block traffic at a higher layer, especially for HTTPS where inspection is required.
Detailed technical explanation
How to think about this question
Security profiles in FortiGate, such as web filtering, application control, and SSL/SSH inspection, are applied per policy and can inspect HTTPS traffic at the application layer. Even if the firewall policy allows port 443, a web filtering profile might block the destination URL or category, or an SSL inspection profile might fail to decrypt the traffic if the server certificate is untrusted. This is a common scenario where the policy appears correct but a security profile silently drops the traffic, often logged under the security profile's own logs rather than the firewall policy logs.
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.
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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 — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: A security profile applied to the policy is blocking the HTTPS traffic. — The correct answer is C because security profiles (such as web filtering, application control, or SSL inspection) applied to a firewall policy can inspect and block HTTPS traffic even when the policy itself allows the service. Since the server is reachable from other VLANs and the policy explicitly permits HTTPS with NAT disabled and logging enabled, the most likely cause is that a security profile is dropping or denying the traffic.
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.
Are there clue words in this question I should notice?
Yes — watch for: "most likely", "always". 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?
Read the scenario before looking for a memorised answer.
About these practice questions
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Last reviewed: Jun 11, 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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