PCNSE Deploy and Configure Firewalls Practice Question
Exhibit
set shared decryption rule MyRule from trust to untrust source 10.1.1.0/24 destination any application ssl decryption forward-proxy
Refer to the exhibit. An administrator has configured this decryption policy but users in the 10.1.1.0/24 subnet receive certificate warnings when accessing HTTPS sites. What is the most likely cause?
⚠ Common exam trap
Palo Alto Networks often tests the distinction between rule configuration issues (like order or application matching) and certificate trust issues, leading candidates to focus on policy settings rather than the fundamental requirement that clients must trust the decryption CA.
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 decryption certificate is not trusted by clients
Certificate warnings occur when the decryption certificate used by the firewall is not trusted by the client machines. In a forward proxy decryption scenario, the firewall generates a new certificate on-the-fly for each HTTPS session, and if that certificate is not installed in the client's trusted root store, the browser will display a security warning. This is the most common cause of certificate warnings in decryption deployments.
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 rule should be at the top of the rulebase
Why it's wrong here
Rule position affects evaluation order, not certificate trust; the firewall still presents its forward-trust certificate, so users see warnings unless that CA certificate is installed on clients. It is tempting because ordering matters for shadowed rules, and placing a decryption rule above a no-decrypt rule would be correct when a broader rule pre-empts it.
- ✗
The destination address should be specific
Why it's wrong here
Destination scope controls which servers are decrypted, not whether clients trust the firewall's certificate; certificate warnings arise from the forward-trust CA not being installed on the endpoints. It is tempting because narrowing destinations is good practice, and it would be correct when a rule must exclude specific sites from decryption.
- ✗
The application should be web-browsing
Why it's wrong here
Application identification does not determine whether the firewall presents a trusted certificate; web-browsing is already the correct match for HTTPS traffic. It is tempting because application filters commonly cause decryption rules to be skipped, and specifying web-browsing would be right when a rule must match only browser traffic rather than all applications.
- ✓
The decryption certificate is not trusted by clients
Why this is correct
An untrusted forward-trust certificate causes browsers to reject the firewall's re-signed certificates, triggering warnings. Since the policy decrypts traffic from 10.1.1.0/24, clients must trust the CA issuing the decryption certificate; without that trust chain installed, every HTTPS site presents an untrusted certificate.
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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.