PCNSE Securing Traffic and App-ID Practice Question
After upgrading PAN-OS from version 9.1 to 10.0, an administrator notices that traffic for an internal custom application is now classified as unknown-tcp instead of the expected custom application. The application was defined using a custom App-ID in the previous version. What is the most likely cause?
⚠ Common exam trap
Watch out — candidates often assume custom App-IDs are backward-compatible across major PAN-OS upgrades, when in reality they often require manual re-creation due to changes in the internal App-ID engine and signature format.
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 custom App-ID is incompatible with the new version and needs to be re-created.
When upgrading PAN-OS from version 9.1 to 10.0, custom App-IDs defined in the previous version are not automatically compatible because the internal App-ID framework and signature format changed significantly between these major versions. The custom application definition must be re-created or re-imported using the new version's tools, as the old custom App-ID object becomes orphaned or non-functional, causing traffic to fall back to unknown-tcp.
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 new version deprecated the application signature.
Why it's wrong here
Palo Alto does not deprecate custom App-IDs automatically.
- ✓
The custom App-ID is incompatible with the new version and needs to be re-created.
Why this is correct
Upgrades can change App-ID engine behavior; custom applications may require redefinition.
- ✗
The firewall license expired after the upgrade.
Why it's wrong here
License expiration affects updates, not existing custom App-IDs.
- ✗
The upgrade reset the firewall configuration.
Why it's wrong here
Upgrades do not reset configurations unless specifically performed.
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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.