PCNSE Decryption and SSL Inspection Practice Question
A company uses SSL Forward Proxy decryption for user traffic. Recently, some users cannot access a specific HTTPS website that uses a self-signed certificate. The firewall's decryption policy is set to 'decrypt' and the action is 'forward proxy'. The firewall does not have the self-signed CA certificate installed. What is the most likely cause of the issue?
⚠ Common exam trap
Palo Alto Networks often tests the distinction between the firewall's ability to validate the server certificate (which requires the server's CA to be trusted) versus the client's trust in the firewall's decryption certificate, leading candidates to confuse client-side trust issues with server-side validation failures.
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 firewall cannot decrypt the session because it does not trust the self-signed certificate of the website.
In SSL Forward Proxy decryption, the firewall must generate a new server certificate on-the-fly to present to the client. To do this, it needs to trust the original server's certificate so it can validate the server's identity and then re-sign the session. Since the website uses a self-signed certificate and the firewall does not have that CA certificate installed, the firewall cannot validate the server's certificate, causing the decryption to fail and the session to be blocked.
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 cannot decrypt the session because it does not trust the self-signed certificate of the website.
Why this is correct
The firewall must trust the server's certificate to re-sign for the client; without the self-signed CA, it cannot.
- ✗
The website is not included in the decryption policy's URL category.
Why it's wrong here
If the URL were not in the policy, traffic would not be decrypted at all, but the issue is about failed decryption.
- ✗
The firewall's decryption certificate is not trusted by the client browsers.
Why it's wrong here
Even if the client trusts the firewall's certificate, the firewall cannot decrypt the server's self-signed certificate.
- ✗
The firewall's forward proxy decryption requires a server certificate that matches the original website.
Why it's wrong here
Forward proxy generates a new certificate for the client; it does not need the original server certificate.
Go deeper
Related to this question
About these practice questions
Courseiva writes every PCNSE question from scratch — 504 in total, each with an explanation and a wrong-answer breakdown. None are copied from real exams or dumps. Learn why practice questions differ from exam dumps →
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.