PCNSE Securing Traffic and App-ID Practice Question
This PCNSE practice question tests your understanding of securing traffic and app-id. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 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.
Option B is correct: Custom App-IDs may not be compatible with the new PAN-OS version and might need to be re-created or updated. Option A is wrong because application signatures are not automatically deprecated without custom App-ID issues. Option C is wrong because the upgrade does not typically reset configurations. Option D is wrong because the license is not directly relevant to App-ID.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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
Static NAT maps one inside address to one outside address.
✗
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: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
Got this wrong? Here's your next step.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related PCNSE NAT questions on configuration and troubleshooting.
Securing Traffic and App-ID — This question tests Securing Traffic and App-ID — Static NAT maps one inside address to one outside address..
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. — Option B is correct: Custom App-IDs may not be compatible with the new PAN-OS version and might need to be re-created or updated. Option A is wrong because application signatures are not automatically deprecated without custom App-ID issues. Option C is wrong because the upgrade does not typically reset configurations. Option D is wrong because the license is not directly relevant to App-ID.
What should I do if I get this PCNSE question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related PCNSE NAT questions on configuration and troubleshooting.
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?
Static NAT maps one inside address to one outside address.
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Question Discussion
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