PCNSA Decryption and Monitoring Practice Question
A security administrator is troubleshooting why some SSL Forward Proxy decrypted sessions are failing with 'certificate unknown' errors. The firewall is configured with a self-signed forward trust certificate. Which two actions should the administrator take to resolve the issue? (Choose two.)
⚠ Common exam trap
The trap here is assuming that enabling decryption on the untrust zone or adjusting decryption profiles will solve certificate trust errors, when the root cause is client-side trust of the forward trust certificate.
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
✓
Install the forward trust certificate's root CA on all client systems.
The 'certificate unknown' error occurs because clients do not trust the forward trust certificate used by the firewall to re-sign decrypted traffic. To fix this, the forward trust certificate must be either signed by a trusted CA or its root CA must be installed on clients. These two actions ensure that clients trust the certificates generated by the firewall, allowing decryption to proceed without errors.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Change the decryption rule action to 'no-decrypt' for affected sites.
Why it's wrong here
Changing the action to no-decrypt would bypass decryption for those sites, eliminating the error but also removing security inspection. This does not resolve the underlying certificate trust issue and reduces visibility. The goal is to fix decryption, not avoid it.
- ✓
Install the forward trust certificate's root CA on all client systems.
Why this is correct
If the forward trust certificate is self-signed, its root CA must be distributed to and trusted by all clients. Without this, clients will not trust the certificates generated by the firewall for decrypted sites, causing 'certificate unknown' errors. This is a common requirement for SSL Forward Proxy decryption.
- ✗
Configure a decryption profile to allow expired certificates.
Why it's wrong here
Allowing expired certificates in the decryption profile affects how the firewall handles expired certificates during decryption, but it does not resolve trust issues with the forward trust certificate. The error 'certificate unknown' indicates a trust problem, not an expiration problem.
- ✓
Import a CA certificate signed by a trusted public CA as the forward trust certificate.
Why this is correct
When the forward trust certificate is self-signed, client browsers do not trust it, leading to certificate errors. Using a certificate signed by a trusted public CA (or an internal enterprise CA that clients trust) ensures that the firewall can generate trusted certificates for decrypted sites, resolving the error.
- ✗
Enable SSL decryption on the untrust zone.
Why it's wrong here
SSL decryption is typically applied to traffic from trust to untrust, not on the untrust zone itself. Enabling decryption on the untrust zone would not address certificate trust issues and could lead to unintended decryption of inbound traffic, which is not the scenario described.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Palo Alto Networks exam blueprint
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.