This PCNSA practice question tests your understanding of securing traffic. 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.
A security administrator notices that traffic from the internal trust zone to the external untrust zone is being allowed despite a security policy rule explicitly denying that traffic. The rule is present in the policy list and the match conditions seem correct. What is the most likely cause of this issue?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
There is an allow rule above the deny rule that matches the traffic first.
Option D is correct because any deny rule placed after a matching allow rule will not be evaluated if the allow rule is hit first. Rule order is critical in PAN-OS. Option A is wrong because removing the rule is not the cause. Option B is wrong because policy is not optional. Option C is wrong because implicit deny exists but only if no rule matches.
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
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
The security policy is not enabled on the firewall.
Why it's wrong here
Security policy is always enforced.
✗
The deny rule was removed from the configuration.
Why it's wrong here
If the rule were removed, it wouldn't be present.
✗
The traffic is matching the implicit deny rule at the end.
Why it's wrong here
Implicit deny would block, not allow.
✓
There is an allow rule above the deny rule that matches the traffic first.
Why this is correct
Rule order evaluation stops on first match; allow rule above the deny will permit traffic.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Standard ACLs match source addresses.
Common exam traps
Common exam trap: ACLs stop at the first match
ACLs are processed top to bottom. The first matching entry wins, and an implicit deny usually exists at the end.
Detailed technical explanation
How to think about this question
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.
KKey Concepts to Remember
Standard ACLs match source addresses.
Extended ACLs can match source, destination, protocol and ports.
The first matching ACL entry is used.
There is usually an implicit deny at the end.
TExam Day Tips
→Check inbound versus outbound direction.
→Read the ACL from top to bottom.
→Look for a broader permit or deny above the intended line.
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
How this comes up in practice
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
Got this wrong? Here's your next step.
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 PCNSA ACL questions on filtering logic and placement.
Securing Traffic — This question tests Securing Traffic — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: There is an allow rule above the deny rule that matches the traffic first. — Option D is correct because any deny rule placed after a matching allow rule will not be evaluated if the allow rule is hit first. Rule order is critical in PAN-OS. Option A is wrong because removing the rule is not the cause. Option B is wrong because policy is not optional. Option C is wrong because implicit deny exists but only if no rule matches.
What should I do if I get this PCNSA question wrong?
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 PCNSA ACL questions on filtering logic and placement.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Standard ACLs match source addresses.
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Question Discussion
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