The correct answer is a firewall policy from WAN to DMZ with source any, destination VIP, and action ACCEPT. This is required because a Virtual IP (VIP) on a FortiGate only defines the static NAT translation rule mapping the public IP to the private IP; it does not, by itself, permit any traffic. The firewall policy must explicitly reference the VIP object as the destination to allow inbound traffic, as the policy evaluation occurs before the destination NAT translation is applied. On the Fortinet NSE 4 Network Security Professional NSE4 exam, this concept tests your understanding of the order of operations—NAT is processed after policy matching—and a common trap is mistakenly using the private IP as the destination in the policy instead of the VIP object. Remember the key rule: the VIP is the destination in the policy, not the real server IP. A useful memory tip is "VIP in the policy, not the private IP"—the policy sees the public address, so the VIP object must be your destination.
NSE4 Firewall Policies and NAT Practice Question
This NSE4 practice question tests your understanding of firewall policies and nat. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 has a web server in the DMZ that needs to be accessible from the internet on port 443 (HTTPS). The administrator configures a Virtual IP (VIP) mapping the public IP 203.0.113.10 to the private IP 10.0.1.10 port 443. Which firewall policy is required to allow inbound traffic?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
A policy from WAN to DMZ with source any, destination VIP, and action ACCEPT
Option B is correct because when a Virtual IP (VIP) is configured in FortiGate, the firewall policy must reference the VIP object as the destination, not the actual private IP. The VIP translates the public IP (203.0.113.10) to the private IP (10.0.1.10), and the policy from WAN to DMZ with destination VIP ensures that inbound traffic is matched and permitted before NAT translation occurs. Without this policy, the VIP alone does not allow traffic; it only defines the translation rule.
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.
✗
A policy from WAN to DMZ with source any, destination IP of the server (10.0.1.10), and action ACCEPT
Why it's wrong here
The policy should use the VIP as destination, not the private IP directly.
✓
A policy from WAN to DMZ with source any, destination VIP, and action ACCEPT
Why this is correct
This policy allows traffic destined to the VIP. The VIP translation occurs before policy lookup, so the policy must allow traffic to the VIP.
Related concept
Read the scenario before looking for a memorised answer.
✗
No firewall policy is needed; the VIP automatically allows traffic
Why it's wrong here
VIPs do not bypass firewall policies; a policy must explicitly allow the traffic.
✗
A policy from DMZ to WAN with source VIP, destination any, and action ACCEPT
Why it's wrong here
This would allow outbound traffic from the server, not inbound.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume a VIP automatically permits traffic or that the policy should use the private IP, but FortiGate requires an explicit firewall policy referencing the VIP object to allow inbound traffic through the NAT mapping.
Detailed technical explanation
How to think about this question
In FortiGate, a Virtual IP (VIP) is a one-to-one or port-based NAT mapping that translates the destination IP/port of incoming packets. The firewall policy must reference the VIP object as the destination to ensure that the policy is evaluated before NAT; if the private IP is used, the policy will not match because the packet's destination is still the public IP. A common real-world scenario is when multiple services (e.g., HTTPS and SSH) are mapped to different private servers using separate VIPs, each requiring its own policy from WAN to the respective VIP.
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: A policy from WAN to DMZ with source any, destination VIP, and action ACCEPT — Option B is correct because when a Virtual IP (VIP) is configured in FortiGate, the firewall policy must reference the VIP object as the destination, not the actual private IP. The VIP translates the public IP (203.0.113.10) to the private IP (10.0.1.10), and the policy from WAN to DMZ with destination VIP ensures that inbound traffic is matched and permitted before NAT translation occurs. Without this policy, the VIP alone does not allow traffic; it only defines the translation rule.
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.
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Question Discussion
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