- A
Create a central SNAT policy with the source as the mail server and the translated IP as the desired address
Why wrong: Central SNAT is a different feature. If policy-based NAT is used, central SNAT should be disabled.
- B
Use a VIP with port forwarding to translate the source
Why wrong: VIP is for destination translation, not source.
- C
In the firewall policy, enable NAT and specify the IP pool as a fixed port range or overload
In policy-based NAT, you can enable NAT and select an IP pool. The pool can be configured for overload (PAT) or fixed port range, but the translated IP is taken from the pool.
- D
Enable NAT on the policy and set the IP pool configuration to use a dynamic IP pool
Why wrong: Dynamic IP pool would assign multiple IPs, not a single fixed IP.
Quick Answer
The answer is to enable NAT in the firewall policy and specify the IP pool as a fixed port range or overload. This is correct because policy-based NAT on FortiGate allows you to override the default source IP (the egress interface address) by binding a specific IP pool directly within the policy’s NAT settings, ensuring the mail server’s traffic uses a fixed, predictable source address. On the Fortinet NSE 4 exam, this scenario tests your understanding of how policy-based NAT differs from central NAT—a common trap is assuming the interface IP is always used, but the question explicitly requires a fixed pool for SMTP. Remember the key distinction: policy-based NAT gives you granular control per policy, while central NAT is global. A useful memory tip is “Policy picks the pool”—if the exam asks for a specific source IP from a pool, always look for the policy’s NAT enablement and pool assignment, not just the interface.
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.
An admin configures a firewall policy to allow SMTP traffic from a mail server to the internet with NAT enabled. External recipients report that the email source IP is the FortiGate's external interface IP. The admin wants the source to be a specific IP from a pool. What should the admin configure?
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
In the firewall policy, enable NAT and specify the IP pool as a fixed port range or overload
Policy-based NAT allows specifying a fixed IP address or IP pool for source NAT. The admin should configure the policy's NAT settings to use a specific IP pool or IP address.
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.
- ✗
Create a central SNAT policy with the source as the mail server and the translated IP as the desired address
Why it's wrong here
Central SNAT is a different feature. If policy-based NAT is used, central SNAT should be disabled.
- ✗
Use a VIP with port forwarding to translate the source
Why it's wrong here
VIP is for destination translation, not source.
- ✓
In the firewall policy, enable NAT and specify the IP pool as a fixed port range or overload
- ✗
Enable NAT on the policy and set the IP pool configuration to use a dynamic IP pool
Why it's wrong here
Dynamic IP pool would assign multiple IPs, not a single fixed IP.
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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Firewall Policies and NAT — study guide chapter
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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: In the firewall policy, enable NAT and specify the IP pool as a fixed port range or overload — Policy-based NAT allows specifying a fixed IP address or IP pool for source NAT. The admin should configure the policy's NAT settings to use a specific IP pool or IP address.
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.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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Last reviewed: Jun 21, 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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