Question 275 of 1,000

Firewall Policies and NAT →mediumMultiple SelectObjective-mapped

Quick Answer

The answer is that the firewall policy must use the VIP as the destination address object, and the VIP must map the external IP and port to the internal server’s private IP and port. This is correct because a Virtual IP for Destination NAT translates an incoming packet’s destination from the FortiGate’s public IP to the internal server’s 10.0.0.10 address, and the policy enforces this translation by referencing the VIP object as the destination. On the Fortinet NSE 4 Network Security Professional exam, this scenario tests your understanding that VIP configuration is separate from policy—many candidates mistakenly think they must also configure a separate destination port in the policy, but the VIP handles port mapping automatically when the external and internal ports match (e.g., 443 to 443). A common trap is confusing source NAT (IP Pool) with destination NAT (VIP); remember that VIPs are for inbound traffic, not outbound. Memory tip: “VIP maps the ‘where to,’ policy decides the ‘who can’—never set the port twice.”

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 FortiGate administrator is configuring a firewall policy to allow inbound HTTPS traffic from the internet to an internal web server. The web server has a private IP address 10.0.0.10. The administrator wants to translate the destination IP to the internal server using a Virtual IP (VIP). Which TWO of the following must be configured for the VIP to work correctly? (Choose two.)

Question 1mediummulti select

Read the full NAT/PAT explanation →

A
An IP Pool must be configured for the web server's return traffic
Why wrong: Return traffic is handled automatically via session state; no IP Pool needed for destination NAT.
B
The VIP must have port forwarding enabled with the external and internal ports set to 443
Why wrong: Port forwarding is optional if the ports are the same; not required for basic VIP operation.
C
The VIP must have the external IP set to a public IP address assigned to the FortiGate's WAN interface
The external IP is the destination IP that inbound traffic hits; it must be an IP on the FortiGate's incoming interface.
D
The firewall policy must use the VIP as the destination address object
The policy's destination must be set to the VIP object to trigger DNAT.
E
The firewall policy must have NAT enabled
Why wrong: NAT on the policy is for source NAT; DNAT is handled by the VIP itself, not the policy's NAT checkbox.

Full breakdown with real-world context →

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 VIP must have the external IP set to a public IP address assigned to the FortiGate's WAN interface

A VIP requires mapping an external IP/port to an internal IP/port. The firewall policy must reference the VIP as the destination and use the VIP's mapped port if different from the incoming port. The VIP must have the correct external IP (the FortiGate's public IP) and internal IP (10.0.0.10). Option C is unnecessary if the external and internal ports are the same (443->443). Option E is for source NAT, not destination NAT.

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.

✗
An IP Pool must be configured for the web server's return traffic
Why it's wrong here
Return traffic is handled automatically via session state; no IP Pool needed for destination NAT.
✗
The VIP must have port forwarding enabled with the external and internal ports set to 443
Why it's wrong here
Port forwarding is optional if the ports are the same; not required for basic VIP operation.
✓
The VIP must have the external IP set to a public IP address assigned to the FortiGate's WAN interface
Why this is correct
The external IP is the destination IP that inbound traffic hits; it must be an IP on the FortiGate's incoming interface.
Related concept
Static NAT maps one inside address to one outside address.
✓
The firewall policy must use the VIP as the destination address object
Why this is correct
The policy's destination must be set to the VIP object to trigger DNAT.
Related concept
Static NAT maps one inside address to one outside address.
✗
The firewall policy must have NAT enabled
Why it's wrong here
NAT on the policy is for source NAT; DNAT is handled by the VIP itself, not the policy's NAT checkbox.

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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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 VIP must have the external IP set to a public IP address assigned to the FortiGate's WAN interface — A VIP requires mapping an external IP/port to an internal IP/port. The firewall policy must reference the VIP as the destination and use the VIP's mapped port if different from the incoming port. The VIP must have the correct external IP (the FortiGate's public IP) and internal IP (10.0.0.10). Option C is unnecessary if the external and internal ports are the same (443->443). Option E is for source NAT, not destination NAT.

What should I do if I get this NSE4 question wrong?

What is the key concept behind this question?

Static NAT maps one inside address to one outside address.

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