This PCNSA practice question tests your understanding of core concepts. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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.
```
> show running security-policy
Rule Name Source Zone Dest Zone App Action
----------------------------------------------------------------
1: Block-SSH any any ssh deny
2: Allow-SSH-Admin trust untrust ssh allow
3: Allow-Web trust untrust web-browsing allow
```
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?
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.
```
> show running security-policy
Rule Name Source Zone Dest Zone App Action
----------------------------------------------------------------
1: Block-SSH any any ssh deny
2: Allow-SSH-Admin trust untrust ssh allow
3: Allow-Web trust untrust web-browsing allow
```
A
Rule 2's application is set to 'ssh' but the service is not 'application-default'
Why wrong: Even if the service is missing, the rule might not match, but the primary issue is rule 1.
B
Rule 1 matches the traffic and is evaluated before rule 2
Since rule 1 has 'any' zones and is higher priority, it blocks SSH before rule 2 is reached.
C
Rule 1 is configured with action 'allow'
Why wrong: The exhibit shows rule 1 action is deny.
D
Rule 2's source zone is incorrectly set to 'dmz'
Why wrong: The exhibit shows source zone 'trust' for rule 2.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Rule 1 matches the traffic and is evaluated before rule 2
Option B is correct because rule 1 matches any SSH traffic (source and destination zones 'any') and is evaluated before rule 2. Since rule 1's action is 'deny', it blocks the traffic before rule 2 can allow it. Option A is incorrect because the service setting does not affect rule matching priority; rule order determines evaluation. Option C is incorrect because the action of rule 1 is 'deny', not 'allow'. Option D is incorrect because even if rule 2's source zone is correct, rule 1 still matches first and blocks the traffic.
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.
✗
Rule 2's application is set to 'ssh' but the service is not 'application-default'
Why it's wrong here
Even if the service is missing, the rule might not match, but the primary issue is rule 1.
✓
Rule 1 matches the traffic and is evaluated before rule 2
Why this is correct
Since rule 1 has 'any' zones and is higher priority, it blocks SSH before rule 2 is reached.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Standard ACLs match source addresses.
✗
Rule 1 is configured with action 'allow'
Why it's wrong here
The exhibit shows rule 1 action is deny.
✗
Rule 2's source zone is incorrectly set to 'dmz'
Why it's wrong here
The exhibit shows source zone 'trust' for rule 2.
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 shows rule 1 action is deny.
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: Rule 1 matches the traffic and is evaluated before rule 2 — Option B is correct because rule 1 matches any SSH traffic (source and destination zones 'any') and is evaluated before rule 2. Since rule 1's action is 'deny', it blocks the traffic before rule 2 can allow it. Option A is incorrect because the service setting does not affect rule matching priority; rule order determines evaluation. Option C is incorrect because the action of rule 1 is 'deny', not 'allow'. Option D is incorrect because even if rule 2's source zone is correct, rule 1 still matches first and blocks the traffic.
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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