The answer is that a different rule with higher priority is matching the traffic and denying it. This occurs because the security rule evaluation order in Palo Alto Networks firewalls processes rules from top to bottom, and the first match is applied; if a higher-priority rule denies the traffic before the rule with log-start enabled is evaluated, the log will still show a deny action due to the log-start entry being generated before the final action is determined. On the PCNSA exam, this scenario tests your understanding of how log-start interacts with rule evaluation order—a common trap is assuming that log-start logs the rule’s own action rather than the traffic’s initial match. The search intent “security rule evaluation order log-start deny” highlights the key pitfall: log-start creates a preliminary log entry, but the actual action depends on which rule matches first. Remember the memory tip: “Log-start logs the attempt, not the outcome—priority decides the route.”
PCNSA Core Concepts Practice Question
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.
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 B is correct because the rule has 'log-start' enabled, which generates a log entry before the actual action is determined. If another rule with higher priority denies the traffic, the log will show the result of the first matching rule. Option A is wrong because the rule itself has action allow, so if it matches, it would allow. Option C is wrong because even if the rule is disabled, it would not produce a log. Option D is wrong because the rule explicitly allows web-browsing.
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 B is correct because the rule has 'log-start' enabled, which generates a log entry before the actual action is determined. If another rule with higher priority denies the traffic, the log will show the result of the first matching rule. Option A is wrong because the rule itself has action allow, so if it matches, it would allow. Option C is wrong because even if the rule is disabled, it would not produce a log. Option D is wrong because the rule explicitly allows web-browsing.
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.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. Refer to the exhibit. An administrator notices that SSH traffic from the trust zone to the untrust zone is being blocked. The administrator expected it to be allowed by rule 2. What is the most likely reason?
easy
A.Rule 2's application is set to 'ssh' but the service is not 'application-default'
✓ B.Rule 1 matches the traffic and is evaluated before rule 2
C.Rule 1 is configured with action 'allow'
D.Rule 2's source zone is incorrectly set to 'dmz'
Why B: Option A is correct because rule 1 has source and destination zones 'any' and matches all SSH traffic, and it is placed before rule 2. Option B is wrong because the action of rule 1 is deny, not allow. Option C is wrong because the rule explicitly denies SSH. Option D is wrong because the rule 2 does allow SSH but never gets evaluated due to rule 1.
Last reviewed: Jun 24, 2026
Question Discussion
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This PCNSA practice question is part of Courseiva's free Palo Alto Networks 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 PCNSA exam.
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