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.
An administrator configures a Virtual IP (VIP) to map the public IP 203.0.113.10 port 8080 to the internal server 192.168.1.100 port 80. External users report they cannot connect. The firewall policy allows inbound traffic to the VIP. What is the MOST likely missing configuration?
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 the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The destination in the firewall policy is set to the public IP directly instead of the VIP object
When a Virtual IP (VIP) is configured, the firewall policy must reference the VIP object as the destination, not the public IP address directly. If the policy uses the public IP (203.0.113.10) as the destination, the FortiGate will not perform the destination NAT translation to the internal server (192.168.1.100). The VIP object contains the mapping logic, so the policy must point to that object for the translation to occur.
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 destination in the firewall policy is set to the public IP directly instead of the VIP object
Why this is correct
Using the raw public IP bypasses the VIP translation. The policy must reference the VIP object.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The VIP is configured with port forwarding disabled
Why it's wrong here
Port forwarding is implicitly enabled when a port mapping is defined.
✗
The server's default gateway is not set to the FortiGate
Why it's wrong here
This would affect return traffic, but the question mentions external users cannot connect at all.
✗
The source NAT is not configured
Why it's wrong here
DNAT does not require source NAT; only destination translation is needed for inbound access.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume the firewall policy should use the public IP as the destination, not realizing that the VIP object must be referenced in the policy for the NAT translation to be applied.
Detailed technical explanation
How to think about this question
Under the hood, a VIP object creates a static destination NAT rule in the FortiGate's kernel forwarding table. The firewall policy's destination must match the VIP object's name, not the pre-NAT public IP, because the policy lookup occurs before NAT translation. If the policy uses the public IP, the packet is forwarded without translation, and the server never receives the packet. In real-world scenarios, administrators often confuse 'destination address' with 'destination interface' or mistakenly use the public IP in the policy, leading to this exact failure.
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.
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: The destination in the firewall policy is set to the public IP directly instead of the VIP object — When a Virtual IP (VIP) is configured, the firewall policy must reference the VIP object as the destination, not the public IP address directly. If the policy uses the public IP (203.0.113.10) as the destination, the FortiGate will not perform the destination NAT translation to the internal server (192.168.1.100). The VIP object contains the mapping logic, so the policy must point to that object for the translation to occur.
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". 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.
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Question Discussion
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