This NSE4 practice question tests your understanding of firewall policies and nat. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
Which of the following describes the implicit deny action in FortiGate firewall policies?
A policy that is automatically created when the first policy is added
Why wrong: Implicit deny exists from the start.
A policy that denies traffic based on the source IP
Why wrong: That's a regular deny policy.
A policy that denies all traffic and can be moved to any position
Why wrong: Implicit deny is always at the bottom and cannot be moved.
A default policy that denies all traffic unless explicitly allowed
Correct description.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
A default policy that denies all traffic unless explicitly allowed
The implicit deny is a default rule at the end of the policy list that denies all traffic not explicitly allowed. It cannot be moved or deleted.
Key principle: ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
A policy that is automatically created when the first policy is added
Why it's wrong here
Implicit deny exists from the start.
A policy that denies traffic based on the source IP
Why it's wrong here
That's a regular deny policy.
A policy that denies all traffic and can be moved to any position
Why it's wrong here
Implicit deny is always at the bottom and cannot be moved.
A default policy that denies all traffic unless explicitly allowed
Why this is correct
Correct description.
Related concept
Standard ACLs match source addresses.
Common exam traps
ACLs are processed top to bottom. The first matching entry wins, and an implicit deny usually exists at the end.
Detailed technical explanation
ACL questions test precision: source, destination, protocol, port and direction. A generally correct ACL can still fail if it is applied on the wrong interface or in the wrong direction.
Key takeaway
ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
Real-world example
A security administrator must allow nursing staff to reach a patient records server while blocking access from the guest Wi-Fi VLAN. After applying an extended ACL, traffic is still blocked from nursing workstations. The ACL was applied outbound instead of inbound on the wrong interface. Questions like this test ACL direction and placement rules.
What to study next
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related NSE4 ACL questions on filtering logic and placement.
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FAQ
Firewall Policies and NAT — This question tests Firewall Policies and NAT — Standard ACLs match source addresses..
The correct answer is: A default policy that denies all traffic unless explicitly allowed — The implicit deny is a default rule at the end of the policy list that denies all traffic not explicitly allowed. It cannot be moved or deleted.
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related NSE4 ACL questions on filtering logic and placement.
Standard ACLs match source addresses.
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Last reviewed: Jun 21, 2026
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