- A
Set the FortiGate to transparent mode
Why wrong: Transparent mode does not support NAT.
- B
Configure a policy route to force traffic through a specific interface
Why wrong: Policy routes do not perform NAT.
- C
Configure a virtual IP mapping internal IPs to the WAN IP
Why wrong: Virtual IPs are for inbound destination NAT.
- D
Enable NAT on the policy from internal to WAN and set the outgoing interface to the WAN interface
This performs source NAT to the WAN IP.
NSE4 System and Network Administration Practice Question
This NSE4 practice question tests your understanding of system and network administration. 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 is set to NAT/Route mode. The admin wants traffic from internal users to the internet to use an IP address on the WAN interface for source NAT. Which configuration is required?
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
Enable NAT on the policy from internal to WAN and set the outgoing interface to the WAN interface
In NAT/Route mode, source NAT (SNAT) is configured by enabling NAT on the firewall policy that governs traffic from the internal network to the WAN interface. When NAT is enabled on the policy and the outgoing interface is set to the WAN interface, FortiGate automatically translates the source IP of internal users to the primary IP address of that WAN interface (or a configured IP pool). This is the standard method for allowing internal users to access the internet with a public IP address.
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.
- ✗
Set the FortiGate to transparent mode
Why it's wrong here
Transparent mode does not support NAT.
- ✗
Configure a policy route to force traffic through a specific interface
Why it's wrong here
Policy routes do not perform NAT.
- ✗
Configure a virtual IP mapping internal IPs to the WAN IP
- ✓
Enable NAT on the policy from internal to WAN and set the outgoing interface to the WAN interface
Why this is correct
This performs source NAT to the WAN IP.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse virtual IP (VIP) for source NAT, but VIP is strictly for destination NAT (inbound traffic), whereas source NAT for outbound traffic requires enabling NAT on the firewall policy.
Detailed technical explanation
How to think about this question
When NAT is enabled on a policy, FortiGate uses the outgoing interface's IP address as the source IP for all matching traffic, unless an IP pool is configured to override it. The NAT operation modifies the source IP and port in the IP header (and recalculates the checksum) before forwarding the packet. In real-world scenarios, this allows multiple internal hosts to share a single public IP via PAT (Port Address Translation), which is essential for conserving IPv4 addresses.
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.
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FAQ
Questions learners often ask
What does this NSE4 question test?
System and Network Administration — This question tests System and Network Administration — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Enable NAT on the policy from internal to WAN and set the outgoing interface to the WAN interface — In NAT/Route mode, source NAT (SNAT) is configured by enabling NAT on the firewall policy that governs traffic from the internal network to the WAN interface. When NAT is enabled on the policy and the outgoing interface is set to the WAN interface, FortiGate automatically translates the source IP of internal users to the primary IP address of that WAN interface (or a configured IP pool). This is the standard method for allowing internal users to access the internet with a public IP address.
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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Last reviewed: Jun 24, 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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