- A
The new version deprecated the application signature.
Why wrong: Palo Alto does not deprecate custom App-IDs automatically.
- B
The custom App-ID is incompatible with the new version and needs to be re-created.
Upgrades can change App-ID engine behavior; custom applications may require redefinition.
- C
The firewall license expired after the upgrade.
Why wrong: License expiration affects updates, not existing custom App-IDs.
- D
The upgrade reset the firewall configuration.
Why wrong: Upgrades do not reset configurations unless specifically performed.
Question 4 of 516
Custom App-ID Compatibility Across PAN-OS Major Upgrades
This PCNSE practice question tests your understanding of securing traffic and app-id. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
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?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"most likely"Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
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.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates 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.
Detailed technical explanation
How to think about this question
Custom App-IDs in PAN-OS rely on a combination of protocol decoders, pattern matching, and behavioral heuristics stored in the application database. Between major versions like 9.1 and 10.0, the internal representation of these signatures changed, and the upgrade process does not automatically migrate custom App-IDs to the new format. In practice, administrators must export custom App-IDs before the upgrade and re-import them using the new version's App-ID editor, or manually redefine the application using the updated signature syntax.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the PCNSE exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
- →
Securing Traffic and App-ID — study guide chapter
Learn the concepts, then practise the questions
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FAQ
Questions learners often ask
What does this PCNSE question test?
Securing Traffic and App-ID — This question tests Securing Traffic and App-ID — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: 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.
What should I do if I get this PCNSE question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
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Last reviewed: Jul 4, 2026
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.
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