- A
The server sends a TCP RST packet to the client.
The firewall records the RST as the session end reason.
- B
The firewall's application override is incorrectly matching the traffic.
An incorrect application override can cause the firewall to apply wrong policy or decoding, leading to resets.
- C
The session reaches the configured idle timeout.
Why wrong: Idle timeout results in a 'aged-out' end reason, not a RST.
- D
A decryption error occurs during SSL handshake.
If decryption fails, the firewall may send a TCP RST to both sides.
- E
The firewall runs out of session resources and starts dropping new sessions.
Why wrong: Resource exhaustion typically causes new sessions to be dropped, not existing sessions to be reset.
Question 83 of 516
Three Causes of Abnormal TCP RST Session Termination
This PCNSE practice question tests your understanding of troubleshoot. 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.
Which THREE factors can cause a session to be terminated abnormally with a 'tcp-rst-from-server' or 'tcp-rst-from-client' flag in the session end reason? (Choose three.)
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The server sends a TCP RST packet to the client.
Option A is correct because a TCP RST packet from the server indicates that the server has abruptly terminated the connection, often due to an application-layer error or a protocol violation. The firewall logs this as 'tcp-rst-from-server' in the session end reason, reflecting that the reset originated from the server side.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 server sends a TCP RST packet to the client.
Why this is correct
The firewall records the RST as the session end reason.
Related concept
Read the scenario before looking for a memorised answer.
- ✓
The firewall's application override is incorrectly matching the traffic.
Why this is correct
An incorrect application override can cause the firewall to apply wrong policy or decoding, leading to resets.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
The session reaches the configured idle timeout.
Why it's wrong here
Idle timeout results in a 'aged-out' end reason, not a RST.
- ✓
A decryption error occurs during SSL handshake.
- ✗
The firewall runs out of session resources and starts dropping new sessions.
Why it's wrong here
Resource exhaustion typically causes new sessions to be dropped, not existing sessions to be reset.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may confuse session termination reasons, assuming any abnormal end is due to resource exhaustion or timeouts, but the question specifically targets TCP RST flags, which are tied to endpoint behavior, not firewall resource management.
Detailed technical explanation
How to think about this question
Under the hood, the firewall tracks TCP state transitions and flags the session end reason based on the last packet seen. A 'tcp-rst-from-server' occurs when the firewall observes a RST packet with the server's IP as the source, which can happen due to application crashes, protocol mismatches, or security policies. In real-world scenarios, this is common when a backend server rejects a request due to invalid data or when a decryption error (option D) causes the server to send a RST after a failed SSL handshake.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the PCNSE exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
Visual reference
What to study next
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FAQ
Questions learners often ask
What does this PCNSE question test?
Troubleshoot — This question tests Troubleshoot — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The server sends a TCP RST packet to the client. — Option A is correct because a TCP RST packet from the server indicates that the server has abruptly terminated the connection, often due to an application-layer error or a protocol violation. The firewall logs this as 'tcp-rst-from-server' in the session end reason, reflecting that the reset originated from the server side.
What should I do if I get this PCNSE question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jul 4, 2026
This PCNSE 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 PCNSE exam.
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