- A
Create an IP pool of type Overload with the range 203.0.113.10 and select it in the policy
An Overload IP pool with a single IP (or range) will perform PAT using that public IP as the source.
- B
Enable NAT on the policy and set the IP pool configuration to use the interface address
Why wrong: Using the interface address would use the IP of the egress interface, not a specific IP.
- C
Configure a Central SNAT rule that matches the source subnet and set the translated address to 203.0.113.10
Why wrong: Central SNAT can achieve this but the question asks for configuration on the firewall policy; policy-based NAT is the context.
- D
Use a VIP to perform destination NAT and set the source IP in the VIP configuration
Why wrong: VIP is for destination NAT, not source NAT.
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 needs to ensure that all traffic from the 10.0.1.0/24 network to the internet uses a specific public IP address (203.0.113.10) as the source IP, with port translation enabled. The FortiGate has multiple WAN interfaces. Which NAT configuration should the admin use on the firewall policy?
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
Create an IP pool of type Overload with the range 203.0.113.10 and select it in the policy
Option A is correct because an IP Pool of type Overload (Port Block Allocation) allows you to specify a single public IP address (203.0.113.10) as the translated source IP for all traffic from 10.0.1.0/24, with port address translation (PAT) enabled. This ensures that all outbound traffic uses that specific IP as the source, regardless of which WAN interface the traffic egresses, and the 'Overload' type automatically performs port translation to multiplex multiple internal hosts behind that single IP.
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.
- ✓
Create an IP pool of type Overload with the range 203.0.113.10 and select it in the policy
Why this is correct
An Overload IP pool with a single IP (or range) will perform PAT using that public IP as the source.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Enable NAT on the policy and set the IP pool configuration to use the interface address
Why it's wrong here
Using the interface address would use the IP of the egress interface, not a specific IP.
- ✗
Configure a Central SNAT rule that matches the source subnet and set the translated address to 203.0.113.10
- ✗
Use a VIP to perform destination NAT and set the source IP in the VIP configuration
Why it's wrong here
VIP is for destination NAT, not source NAT.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse Central SNAT rules (which are applied globally and not tied to a specific firewall policy) with policy-based IP Pool configuration, leading them to select Option C, even though the question explicitly requires the NAT configuration to be set on the firewall policy itself.
Detailed technical explanation
How to think about this question
An IP Pool of type Overload (also called Port Block Allocation or PAT pool) uses a single IP address and dynamically assigns unique source ports for each session, allowing up to ~65,000 concurrent sessions per IP. This is distinct from 'Fixed Port Range' or 'One-to-One' pool types, which do not perform port translation. In real-world scenarios, this is critical when a specific public IP must be used for whitelisting or logging purposes, and the FortiGate has multiple WAN interfaces where the egress interface might vary due to routing or SD-WAN rules.
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.
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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 — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Create an IP pool of type Overload with the range 203.0.113.10 and select it in the policy — Option A is correct because an IP Pool of type Overload (Port Block Allocation) allows you to specify a single public IP address (203.0.113.10) as the translated source IP for all traffic from 10.0.1.0/24, with port address translation (PAT) enabled. This ensures that all outbound traffic uses that specific IP as the source, regardless of which WAN interface the traffic egresses, and the 'Overload' type automatically performs port translation to multiplex multiple internal hosts behind that single IP.
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.
About these practice questions
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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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