PCNSA Decryption and Monitoring Practice Question
A company uses SSL Forward Proxy decryption. The firewall's decryption certificate expires. What immediate impact does this have on traffic?
⚠ Common exam trap
A common mix-up: candidates assume decryption stops or traffic is blocked, but Palo Alto Networks firewalls continue to proxy traffic with the expired certificate, causing client-side warnings rather than a firewall-enforced block.
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
✓
Users receive certificate warnings when accessing HTTPS sites.
When the firewall's SSL Forward Proxy decryption certificate expires, the firewall can no longer present a valid certificate to clients during the SSL/TLS handshake. Browsers and applications will detect the expired certificate and display certificate warnings or errors to users, but the firewall may still attempt to decrypt traffic using the expired certificate, causing trust failures. This is the immediate impact because the firewall does not block traffic by default; it continues to proxy the connection, but the client rejects the invalid certificate.
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 logs a critical system alert.
Why it's wrong here
An expired decryption certificate causes the firewall to block or reset decrypted sessions, so traffic fails rather than merely generating an alert. It is tempting because expiry is a certificate-lifecycle event that logging surfaces, but logging is a side effect; the immediate impact is session failure for forward-proxy-decrypted flows.
- ✓
Users receive certificate warnings when accessing HTTPS sites.
Why this is correct
SSL Forward Proxy presents the firewall's signing certificate to clients in place of the real server certificate. Once that certificate expires, clients cannot validate the chain, so browsers display certificate warnings and users must manually bypass them before HTTPS pages load.
- ✗
Decryption stops working and all SSL traffic is blocked.
Why it's wrong here
With SSL Forward Proxy, an expired firewall decryption certificate causes the firewall to present an untrusted certificate to clients, so the forward proxy cannot establish the trusted session and decryption fails; sessions are typically reset rather than all SSL traffic being blocked. It is tempting because decryption genuinely halts, but the correct answer names the certificate-trust failure mechanism.
- ✗
The firewall automatically renews the certificate from the CA.
Why it's wrong here
The firewall cannot renew its own forward proxy decryption certificate; renewal requires generating a new certificate and re-signing it with the CA, then importing it. It is tempting because automated certificate management exists elsewhere, but PAN-OS performs no such self-renewal, so decryption breaks until an administrator intervenes.
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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.