This PCNSA practice question tests your understanding of core concepts. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. 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.
Exhibit
Refer to the exhibit.
```
! Firewall configuration snippet
security-rule {
name Allow-Web;
source-zone trust;
destination-zone dmz;
source-address 10.0.0.0/24;
destination-address 172.16.1.0/24;
application web-browsing;
service application-default;
action allow;
log-start;
log-end;
}
```
Refer to the exhibit. An administrator observes that HTTP requests from the 10.0.0.0/24 network to the 172.16.1.0/24 network are being logged but the logs show that the action taken is 'deny'. What is the most likely cause?
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.
Exhibit
Refer to the exhibit.
```
! Firewall configuration snippet
security-rule {
name Allow-Web;
source-zone trust;
destination-zone dmz;
source-address 10.0.0.0/24;
destination-address 172.16.1.0/24;
application web-browsing;
service application-default;
action allow;
log-start;
log-end;
}
```
A
The rule 'Allow-Web' is disabled
Why wrong: If disabled, it would not generate logs.
B
The application 'web-browsing' is not correctly identified
Why wrong: The rule uses application 'web-browsing', but misidentification would not cause a deny; it might result in no match.
C
The rule 'Allow-Web' is configured with action 'deny'
Why wrong: The exhibit clearly shows action allow.
D
A different rule with higher priority is matching the traffic and denying it
Even though this rule matches, if a higher-priority rule denies the traffic, the log will reflect the deny from the first matching rule.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
A different rule with higher priority is matching the traffic and denying it
Option D is correct because in Palo Alto Networks firewalls, rules are evaluated in order. If a rule with higher priority (e.g., an implicit deny or a more specific rule) matches first, it will deny the traffic before reaching the 'Allow-Web' rule. The log entry shows the action taken by the first matching rule. Option A is incorrect because if the rule were disabled, it would not produce a log entry at all. Option B is incorrect because the rule already has application 'web-browsing' configured; identification issues would not cause a deny action. Option C is incorrect because if the rule had action 'deny', it would not be named 'Allow-Web' and would not log as deny due to a different rule.
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 rule 'Allow-Web' is disabled
Why it's wrong here
If disabled, it would not generate logs.
✗
The application 'web-browsing' is not correctly identified
Why it's wrong here
The rule uses application 'web-browsing', but misidentification would not cause a deny; it might result in no match.
✗
The rule 'Allow-Web' is configured with action 'deny'
Why it's wrong here
The exhibit clearly shows action allow.
✓
A different rule with higher priority is matching the traffic and denying it
Why this is correct
Even though this rule matches, if a higher-priority rule denies the traffic, the log will reflect the deny from the first matching rule.
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.
Trap categories for this question
Command / output trap
The exhibit clearly shows action allow.
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.
Core Concepts — This question tests Core Concepts — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: A different rule with higher priority is matching the traffic and denying it — Option D is correct because in Palo Alto Networks firewalls, rules are evaluated in order. If a rule with higher priority (e.g., an implicit deny or a more specific rule) matches first, it will deny the traffic before reaching the 'Allow-Web' rule. The log entry shows the action taken by the first matching rule. Option A is incorrect because if the rule were disabled, it would not produce a log entry at all. Option B is incorrect because the rule already has application 'web-browsing' configured; identification issues would not cause a deny action. Option C is incorrect because if the rule had action 'deny', it would not be named 'Allow-Web' and would not log as deny due to a different rule.
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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