The answer is to disable NAT, define the correct source and destination interfaces, and apply security profiles to the policy. When traffic between two internal subnets must be inspected without source IP translation, NAT must be explicitly disabled on the firewall policy because FortiGate policies enable NAT by default on outbound interfaces; disabling it preserves the original source IP (e.g., 10.0.1.x) when communicating with 10.0.2.x. The correct source and destination interfaces must also be specified to ensure the policy applies only to the intended internal zones, while security profiles like antivirus and IPS are required to perform the actual inspection. On the Fortinet NSE 4 exam, this scenario tests your understanding of policy-based NAT control versus central NAT, with a common trap being that candidates forget to disable NAT on internal-to-internal policies. A helpful memory tip: "Internal traffic, no translation—disable NAT, add inspection."
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.
An admin wants to ensure that traffic between two internal subnets (10.0.1.0/24 and 10.0.2.0/24) is inspected by the FortiGate but does not have its source IP translated. Which THREE configuration elements are required? (Choose three.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
NAT disabled on that policy
Option A is correct because when traffic between two internal subnets does not require source IP translation, NAT must be explicitly disabled on the firewall policy. By default, FortiGate policies may have NAT enabled (especially on outbound interfaces), so disabling NAT ensures the original source IP (10.0.1.x) is preserved when communicating with 10.0.2.x. This is configured by setting the 'set nat enable' option to 'disable' in the policy or unchecking NAT in the GUI.
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.
✓
NAT disabled on that policy
Why this is correct
To avoid source IP translation, NAT must be disabled.
Related concept
Read the scenario before looking for a memorised answer.
✗
A static route for each subnet on the FortiGate
Why it's wrong here
If subnets are directly connected, no static route is needed.
A firewall policy allowing traffic between the two subnets
Why this is correct
A policy is required to permit and inspect traffic.
Related concept
Read the scenario before looking for a memorised answer.
✓
Security profiles (e.g., antivirus, IPS) applied to the policy
Why this is correct
Inspection is achieved by applying security profiles.
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 assume static routes are always needed for inter-subnet routing, but FortiGate automatically creates connected routes for directly attached subnets, making static routes unnecessary in this scenario.
Detailed technical explanation
How to think about this question
When NAT is disabled on a FortiGate policy, the firewall performs route-based forwarding without modifying the source or destination IP addresses, relying solely on the routing table to forward packets between subnets. This is typical for internal-to-internal traffic where private IPs must remain intact for logging, policy enforcement, or application compatibility. Security profiles (option E) are essential for inspection because they enable deep packet inspection (e.g., antivirus, IPS) on the traffic, which is the core requirement—without them, traffic would be allowed but not inspected.
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.
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: NAT disabled on that policy — Option A is correct because when traffic between two internal subnets does not require source IP translation, NAT must be explicitly disabled on the firewall policy. By default, FortiGate policies may have NAT enabled (especially on outbound interfaces), so disabling NAT ensures the original source IP (10.0.1.x) is preserved when communicating with 10.0.2.x. This is configured by setting the 'set nat enable' option to 'disable' in the policy or unchecking NAT in the GUI.
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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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.
Question Discussion
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