- A
The forward trust certificate has expired or is not trusted by the clients in Branch Office A.
Why wrong: Certificate expiration or trust issues would affect all users, not just Branch Office A, and would typically result in certificate warnings, not handshake failures.
- B
The decryption profile for Branch Office A is configured with an incorrect cipher suite that is not supported by the external websites.
Why wrong: Incorrect cipher suites would cause different errors, and the profile is identical to working branches.
- C
Traffic from Branch Office A is asymmetrically routed, causing the TLS handshake to be incomplete.
Asymmetric routing can cause the firewall to see only one side of the TCP handshake, leading to SSL handshake failures.
- D
The decryption policy rule for Branch Office A is missing the 'ssl-decrypt' action.
Why wrong: The policy is identical to others that work, so this is unlikely.
Quick Answer
The answer is asymmetric routing causing an incomplete TLS handshake. This is correct because SSL forward proxy decryption requires the firewall to see both the client SYN and the server SYN-ACK to establish a TCP connection and then perform the TLS handshake; when traffic from Branch Office A takes a different return path—such as egressing through the data center firewall but returning via a direct internet breakout or another MPLS link—the firewall never sees the server’s SYN-ACK, so it cannot complete the three-way handshake, leading to SSL handshake failures and peer certificate chain validation errors in the logs. On the PCNSE exam, this scenario tests your understanding of how stateful inspection and proxy-based decryption depend on symmetric traffic flows; a common trap is to blame certificate issues or policy misconfigurations when the decryption policy and certificates are identical across branches. Remember the memory tip: “One-way traffic breaks the proxy—if the SYN-ACK doesn’t come back, the handshake will crack.”
PCNSE Decryption and SSL Inspection Practice Question
This PCNSE practice question tests your understanding of decryption and ssl inspection. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
You are a network security engineer at a multinational corporation. The company has a main data center and three branch offices connected via MPLS. The firewall at the data center is a PA-5250 running PAN-OS 10.2. The firewall is configured for SSL Forward Proxy decryption of all outbound HTTPS traffic from internal users to the internet. Recently, users in Branch Office A report that they cannot access several external HTTPS websites, while users at other branches and the data center have no issues. The decryption policy for Branch Office A is identical to the others. You check the decryption statistics and see that for Branch Office A, the number of 'SSL handshake failures' is high. You also notice that the firewall's system log shows errors like 'peer certificate chain validation failure' for sessions from Branch Office A. The firewall has a forward trust certificate issued by an internal CA, and the internal CA certificate is installed on all clients. What is the most likely cause of this issue?
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 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
Traffic from Branch Office A is asymmetrically routed, causing the TLS handshake to be incomplete.
C is correct because asymmetric routing causes the firewall to see only one side of the TCP handshake, preventing it from completing the TLS handshake. When traffic from Branch Office A takes a different return path (e.g., via another MPLS link or direct internet breakout), the firewall cannot associate the server's SYN-ACK with the original client SYN, leading to SSL handshake failures and 'peer certificate chain validation failure' errors in the logs. The decryption policy and certificates are identical across branches, so the issue is specific to the network path.
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 forward trust certificate has expired or is not trusted by the clients in Branch Office A.
Why it's wrong here
Certificate expiration or trust issues would affect all users, not just Branch Office A, and would typically result in certificate warnings, not handshake failures.
- ✗
The decryption profile for Branch Office A is configured with an incorrect cipher suite that is not supported by the external websites.
Why it's wrong here
Incorrect cipher suites would cause different errors, and the profile is identical to working branches.
- ✓
Traffic from Branch Office A is asymmetrically routed, causing the TLS handshake to be incomplete.
- ✗
The decryption policy rule for Branch Office A is missing the 'ssl-decrypt' action.
Why it's wrong here
The policy is identical to others that work, so this is unlikely.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often blame certificate trust or decryption profile misconfigurations first, overlooking that asymmetric routing is a common network-layer cause of SSL decryption failures even when all security policies and certificates are correctly configured.
Detailed technical explanation
How to think about this question
Asymmetric routing breaks SSL forward proxy because the firewall must see both the client SYN and the server SYN-ACK to build the TCP state machine and perform the TLS handshake. When the return path bypasses the firewall, the firewall never receives the server's certificate, so it cannot validate or re-sign it, resulting in 'peer certificate chain validation failure' and incomplete SSL handshakes. In PAN-OS, this can be diagnosed by checking the session browser for 'tcp-state: SYN_SENT' or 'tcp-state: TIME_WAIT' without a corresponding server-side state, and by verifying that the firewall's routing table shows symmetric paths for the affected traffic.
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 small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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FAQ
Questions learners often ask
What does this PCNSE question test?
Decryption and SSL Inspection — This question tests Decryption and SSL Inspection — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Traffic from Branch Office A is asymmetrically routed, causing the TLS handshake to be incomplete. — C is correct because asymmetric routing causes the firewall to see only one side of the TCP handshake, preventing it from completing the TLS handshake. When traffic from Branch Office A takes a different return path (e.g., via another MPLS link or direct internet breakout), the firewall cannot associate the server's SYN-ACK with the original client SYN, leading to SSL handshake failures and 'peer certificate chain validation failure' errors in the logs. The decryption policy and certificates are identical across branches, so the issue is specific to the network path.
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.
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?
Read the scenario before looking for a memorised answer.
About these practice questions
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Last reviewed: Jun 11, 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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