The answer is that the firewall policy’s destination is set to the real server IP (10.0.1.10) instead of the VIP object. This causes a VIP destination policy misconfiguration leading to timeout because the FortiGate must match traffic against the VIP as the destination address in the policy; when the policy points to the internal server IP, the session never triggers the destination NAT translation, so external packets are dropped or fail to reach the mapped port 8080. On the Fortinet NSE 4 Network Security Professional NSE4 exam, this scenario tests your understanding of VIP policy flow—the policy must reference the VIP object, not the real server, and the destination port should match the original port 80, not the mapped port. A common trap is assuming the policy needs the mapped port, but the key is that the VIP handles the port translation automatically. Memory tip: “Policy sees the public face, not the private place”—always set the destination to the VIP object.
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 configures a VIP to map 203.0.113.10:80 to 10.0.1.10:8080. However, when external users connect to http://203.0.113.10, they receive a connection timeout. The firewall policy allows the traffic. 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.
Why wrong: VIPs are typically bound to the incoming interface (WAN), so that should be correct.
B
The source NAT is not configured
Why wrong: Source NAT is not required for inbound traffic; destination NAT is what matters.
C
The firewall policy's destination is set to the real server IP (10.0.1.10) instead of the VIP object
The policy must use the VIP as the destination address for the destination NAT to work correctly. If it uses the real server IP, the traffic bypasses the VIP translation.
D
The internal server is not listening on port 8080
Why wrong: The server might be listening, but the timeout suggests no response; however, the policy issue is more likely.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The firewall policy's destination is set to the real server IP (10.0.1.10) instead of the VIP object
The most likely cause is that the destination port in the policy is not set to the mapped port (8080) or the VIP is not properly associated. The policy must reference the VIP as the destination address, and if the policy uses the original port 80 instead of the mapped port, it might not match correctly. But the typical issue is that the policy needs to have the VIP as the destination address, not the real server IP. Alternatively, the VIP configuration might be missing the port mapping. Option A is common: the policy destination is set to the real server IP instead of the VIP object.
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 VIP is configured on the wrong interface
Why it's wrong here
VIPs are typically bound to the incoming interface (WAN), so that should be correct.
✗
The source NAT is not configured
Why it's wrong here
Source NAT is not required for inbound traffic; destination NAT is what matters.
✓
The firewall policy's destination is set to the real server IP (10.0.1.10) instead of the VIP object
Why this is correct
The policy must use the VIP as the destination address for the destination NAT to work correctly. If it uses the real server IP, the traffic bypasses the VIP translation.
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.
✗
The internal server is not listening on port 8080
Why it's wrong here
The server might be listening, but the timeout suggests no response; however, the policy issue is more likely.
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.
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 firewall policy's destination is set to the real server IP (10.0.1.10) instead of the VIP object — The most likely cause is that the destination port in the policy is not set to the mapped port (8080) or the VIP is not properly associated. The policy must reference the VIP as the destination address, and if the policy uses the original port 80 instead of the mapped port, it might not match correctly. But the typical issue is that the policy needs to have the VIP as the destination address, not the real server IP. Alternatively, the VIP configuration might be missing the port mapping. Option A is common: the policy destination is set to the real server IP instead of the VIP object.
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
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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 administrator configures a VIP for port forwarding: public IP 203.0.113.10 port 8080 to internal server 10.0.1.10 port 80. External users can connect to http://203.0.113.10:8080 but receive a timeout. The firewall policy allows traffic from any to the VIP on destination port 8080. The internal server is reachable from internal hosts. What is the most likely problem?
hard
A.The internal server is not running a web server
B.The VIP is not associated with the policy
✓ C.The policy destination service is set to HTTP (port 80) instead of port 8080
D.The source NAT is not configured
Why C: Option C is correct because the firewall policy must match the destination port of the incoming traffic. External users connect to port 8080 on the VIP, but if the policy's destination service is set to HTTP (port 80), the policy will not match traffic destined for port 8080. Even though the VIP translates the destination to port 80 on the internal server, the firewall policy evaluation occurs before NAT translation, so the policy must match the original destination port (8080).
Variation 2. 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?
medium
✓ A.The destination in the firewall policy is set to the public IP directly instead of the VIP object
B.The VIP is configured with port forwarding disabled
C.The server's default gateway is not set to the FortiGate
D.The source NAT is not configured
Why A: 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.
Last reviewed: Jun 21, 2026
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