The answer is Policy 1. This is correct because FortiGate firewall policies operate on a first-match order, meaning the device evaluates policies sequentially by their ID number and applies the first rule where all conditions match. Here, traffic from source 10.0.1.5 to destination 172.16.0.1 matches Policy 1’s source range of 10.0.0.0/8 and its destination of “any,” so the action “accept” is applied immediately, and no further policies are checked—even though Policy 2 is a more specific deny rule. On the Fortinet NSE 4 Network Security Professional exam, this concept tests your understanding of policy evaluation order and the critical distinction that a broader allow rule with a lower ID will override a more specific deny rule with a higher ID. A common trap is assuming the most specific rule wins, but in FortiGate, sequence number determines priority, not specificity. Memory tip: “First ID wins—order beats precision.”
NSE4 Firewall Policies and NAT Practice Question
This NSE4 practice question tests your understanding of firewall policies and nat. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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.
During a security audit, the administrator runs the command 'diagnose firewall policy list' and sees the following output:
policy id=1: allow from port1 to port2, src=10.0.0.0/8, dst=any, action=accept
policy id=2: deny from port1 to port2, src=10.0.0.0/8, dst=172.16.0.0/12, action=deny
policy id=3: allow from port1 to port2, src=any, dst=any, action=accept
A host with IP 10.0.1.5 sends traffic to 172.16.0.1. Which policy will match?
Why wrong: Policy 3 would match if neither 1 nor 2 matched, but policy 1 matches first.
B
Policy 1
The traffic matches policy 1 because the source is within 10.0.0.0/8 and destination is any. Policy 2 is more specific but comes after policy 1, and FortiGate uses first-match.
C
Implicit deny
Why wrong: Implicit deny is only hit if no policy matches; policy 1 matches.
D
Policy 2
Why wrong: Policy 2 is more specific but comes after policy 1; first-match prevails.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Policy 1
Policy 1 matches because the source IP 10.0.1.5 falls within the 10.0.0.0/8 range, the destination IP 172.16.0.1 is not explicitly matched by policy 2's destination of 172.16.0.0/12 (since 172.16.0.1 is the network address itself and is included, but policy 2 is a deny and is evaluated before policy 3; however, policy 1 is evaluated first due to its lower ID, and since it matches both source and destination with action accept, the traffic is permitted by policy 1 before reaching policy 2). In FortiGate, policies are evaluated sequentially by ID, and the first match is applied.
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.
✗
Policy 3
Why it's wrong here
Policy 3 would match if neither 1 nor 2 matched, but policy 1 matches first.
✓
Policy 1
Why this is correct
The traffic matches policy 1 because the source is within 10.0.0.0/8 and destination is any. Policy 2 is more specific but comes after policy 1, and FortiGate uses first-match.
Related concept
Read the scenario before looking for a memorised answer.
✗
Implicit deny
Why it's wrong here
Implicit deny is only hit if no policy matches; policy 1 matches.
✗
Policy 2
Why it's wrong here
Policy 2 is more specific but comes after policy 1; first-match prevails.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume a deny rule with a more specific destination will override a broader allow rule, forgetting that FortiGate uses first-match logic based on policy ID order, not longest-prefix matching or specificity.
Detailed technical explanation
How to think about this question
FortiGate firewall policies are evaluated in sequential order based on policy ID (lowest to highest) unless a different order is configured. The destination 172.16.0.1 is indeed within the 172.16.0.0/12 subnet, but because policy 1 (ID=1) matches the source and destination (dst=any) before policy 2 (ID=2) is checked, the traffic is accepted. This demonstrates the importance of policy ordering: a more specific deny rule placed after a broader allow rule will not block traffic that matches the earlier allow rule.
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: Policy 1 — Policy 1 matches because the source IP 10.0.1.5 falls within the 10.0.0.0/8 range, the destination IP 172.16.0.1 is not explicitly matched by policy 2's destination of 172.16.0.0/12 (since 172.16.0.1 is the network address itself and is included, but policy 2 is a deny and is evaluated before policy 3; however, policy 1 is evaluated first due to its lower ID, and since it matches both source and destination with action accept, the traffic is permitted by policy 1 before reaching policy 2). In FortiGate, policies are evaluated sequentially by ID, and the first match is applied.
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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