This PCNSA practice question tests your understanding of securing traffic. 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.
Log entry:
Time: 2024-03-01 10:00:00
Source IP: 10.1.1.100
Destination IP: 203.0.113.50
Application: ssl
Action: allow
Session End Reason: tcp-rst-from-client
Bytes Sent: 1024
Bytes Received: 10240
Context: The security policy allows all outbound traffic. The client is a web browser.
Based on the log entry, what is the most likely reason for the TCP reset from the client?
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.
Log entry:
Time: 2024-03-01 10:00:00
Source IP: 10.1.1.100
Destination IP: 203.0.113.50
Application: ssl
Action: allow
Session End Reason: tcp-rst-from-client
Bytes Sent: 1024
Bytes Received: 10240
Context: The security policy allows all outbound traffic. The client is a web browser.
A
The connection timed out.
Why wrong: Timeout would log tcp-timeout, not tcp-rst-from-client.
B
The security policy blocked the traffic.
Why wrong: The action is allow, so not blocked.
C
The web server sent a reset to the client.
Why wrong: This would log tcp-rst-from-server.
D
The client detected a certificate error and closed the connection.
Client resets can occur due to SSL/TLS handshake failures.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The client detected a certificate error and closed the connection.
The TCP reset from the client indicates the client terminated the connection. In SSL/TLS traffic, a common reason is a certificate error during the handshake. The client detects an invalid or untrusted certificate and sends a TCP reset to close the connection. Option A is incorrect because a timeout would show tcp-timeout. Option B is incorrect because a security policy block would show a deny action or drop. Option C is incorrect because a server-initiated reset would show tcp-rst-from-server.
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 connection timed out.
Why it's wrong here
Timeout would log tcp-timeout, not tcp-rst-from-client.
The client detected a certificate error and closed the connection.
Why this is correct
Client resets can occur due to SSL/TLS handshake failures.
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.
Visual reference
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: The client detected a certificate error and closed the connection. — The TCP reset from the client indicates the client terminated the connection. In SSL/TLS traffic, a common reason is a certificate error during the handshake. The client detects an invalid or untrusted certificate and sends a TCP reset to close the connection. Option A is incorrect because a timeout would show tcp-timeout. Option B is incorrect because a security policy block would show a deny action or drop. Option C is incorrect because a server-initiated reset would show tcp-rst-from-server.
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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