NSE4 Firewall Policies and NAT Practice Question
A FortiGate administrator needs to create a firewall policy that allows traffic from the internal network to the DMZ. The internal network is 10.0.0.0/24 and the DMZ network is 172.16.0.0/24. Which source and destination address objects should be used in the policy?
⚠ Common exam trap
The trap here is reversing the source and destination or using 'all' when a specific subnet 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
✓
Source: 10.0.0.0/24, Destination: 172.16.0.0/24
The firewall policy must match the specific source and destination networks to allow only the desired traffic. Using the internal subnet as source and DMZ subnet as destination creates a precise policy. Other combinations either reverse the direction or are too permissive, failing to meet the requirement.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Source: 172.16.0.0/24, Destination: 10.0.0.0/24
Why it's wrong here
This reverses the source and destination. The policy would allow traffic from the DMZ to the internal network, which is the opposite of what is needed. While such a policy might be useful for return traffic, firewall policies are stateful, so return traffic is automatically allowed. The requirement is for internal to DMZ, so this is incorrect.
- ✗
Source: all, Destination: all
Why it's wrong here
Using 'all' for both source and destination would allow any traffic from any source to any destination, which is overly permissive and does not meet the requirement of allowing only internal to DMZ traffic. This would create a security risk and is not the correct configuration for a specific policy.
- ✗
Source: 10.0.0.0/24, Destination: all
Why it's wrong here
This allows internal traffic to any destination, not just the DMZ. It is broader than required and could allow unintended access to the internet or other networks. The requirement is specifically to allow traffic to the DMZ, so the destination should be limited to the DMZ subnet.
- ✓
Source: 10.0.0.0/24, Destination: 172.16.0.0/24
Why this is correct
This policy correctly matches the internal network as the source and the DMZ network as the destination. It restricts traffic to the intended flow. The addresses should be defined as firewall address objects, but the subnets are the correct values. This is the precise configuration required.
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Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Fortinet exam blueprint
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.