PCNSA Decryption and Monitoring Practice Question
Exhibit
Refer to the exhibit.
```
admin@PA-500> show decryption statistics
Decryption Statistics:
Total Sessions Decrypted: 1500
Total Sessions Failed: 50
Failed Reasons:
handshake_failure: 30
certificate_unknown: 15
decryption_error: 5
```An administrator runs the command and sees the above output. What is the most likely cause of the large number of handshake failures?
⚠ Common exam trap
Watch out — candidates often confuse handshake failures with certificate validation issues, but handshake failures specifically indicate a failure in the initial negotiation phase (e.g., cipher mismatch or protocol version incompatibility), not a trust or CRL problem.
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 is using an unsupported cipher suite.
The output shows a large number of handshake failures, which typically occur during the SSL/TLS handshake when the client and server cannot agree on a common cipher suite. If the server only supports weak or outdated ciphers that the firewall's decryption policy does not allow, or if the firewall's SSL forward proxy engine does not support the server's chosen cipher, the handshake will fail. This is the most likely cause because cipher suite mismatch is a common source of handshake failures in decryption environments.
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 firewall's CRL server is unreachable.
Why it's wrong here
Unreachable CRL would cause certificate_unknown, not handshake_failure.
- ✓
The server is using an unsupported cipher suite.
Why this is correct
Cipher mismatches commonly cause handshake failures.
- ✗
The decryption policy is not matching the traffic.
Why it's wrong here
If the traffic doesn't match, no decryption attempt occurs.
- ✗
The firewall's certificate is not trusted by clients.
Why it's wrong here
Client trust issues cause certificate_unknown, not handshake_failure.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.