The answer is to create two IP pool objects, POOL1 and POOL2, and then configure separate firewall policies for each source subnet. This is correct because policy-based NAT in FortiOS ties the IP pool directly to a firewall policy; you cannot assign multiple IP pools to a single policy for different source subnets. Instead, you must create distinct policies—one for 192.168.1.0/24 using POOL1 and another for 192.168.2.0/24 using POOL2—each with its own NAT settings. On the Fortinet NSE 4 exam, this scenario tests your understanding that policy-based NAT requires a one-to-one mapping between a source subnet and a firewall policy, unlike central NAT. A common trap is assuming a single policy can handle multiple pools by using policy routes or address groups, but the exam expects separate policies for each pool. Remember the memory tip: “One pool per policy, one policy per subnet” to avoid mixing NAT assignments.
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 is configured with policy-based NAT and multiple IP pools. The administrator wants traffic from the 192.168.1.0/24 subnet to use IP pool 'POOL1' (203.0.113.1-203.0.113.10) and traffic from 192.168.2.0/24 to use IP pool 'POOL2' (203.0.113.11-203.0.113.20). Which THREE steps are necessary?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Create two firewall policies, one for each subnet
Option A is correct because policy-based NAT requires separate firewall policies to apply different IP pools to different source subnets. Each firewall policy can have its own NAT settings, including a specific IP pool, allowing traffic from 192.168.1.0/24 to use POOL1 and traffic from 192.168.2.0/24 to use POOL2.
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 two firewall policies, one for each subnet
Why this is correct
Each policy will define its source subnet and NAT with the appropriate IP pool.
Related concept
Read the scenario before looking for a memorised answer.
✓
In each policy, enable NAT and select the corresponding IP pool
Why this is correct
This ties the policy to the IP pool.
Related concept
Read the scenario before looking for a memorised answer.
✗
Configure a single firewall policy with both subnets in the source address group
Why it's wrong here
A single policy cannot use different IP pools for different source subnets.
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may think a single policy with multiple source addresses can apply different NAT pools, but FortiGate policy-based NAT requires separate policies for distinct NAT configurations.
Detailed technical explanation
How to think about this question
In policy-based NAT, each firewall policy independently controls NAT behavior, including the ability to reference an IP pool for source NAT (SNAT). The IP pool object defines a range of translated addresses, and the FortiGate uses a round-robin or sequential allocation algorithm to assign addresses from the pool to sessions. This granularity is essential when different subnets must egress with different public IP ranges, such as for multi-tenant environments or compliance requirements.
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.
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 two firewall policies, one for each subnet — Option A is correct because policy-based NAT requires separate firewall policies to apply different IP pools to different source subnets. Each firewall policy can have its own NAT settings, including a specific IP pool, allowing traffic from 192.168.1.0/24 to use POOL1 and traffic from 192.168.2.0/24 to use POOL2.
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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Question Discussion
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