The answer is to create a custom application signature and ensure App-ID is enabled to inspect traffic. This is required because App-ID identifies applications through multiple mechanisms—signatures, protocol decoders, and behavioral analysis—rather than relying solely on port numbers. When an application shifts to a non-standard port, the default port-based classification fails, so a custom signature must be defined to match the application’s unique traffic patterns, while App-ID must remain active to perform deep packet inspection beyond the port. On the PCNSA exam, this tests your understanding that App-ID is port-agnostic; a common trap is assuming that simply allowing the port or using a predefined application object will suffice. Remember the memory tip: “Ports don’t define the app, signatures do”—so when the port changes, you must build a custom signature to keep App-ID accurate.
PCNSA App-ID and Content-ID Practice Question
This PCNSA practice question tests your understanding of app-id and content-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.
Which TWO are required for accurate application identification when an application uses non-standard ports?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Enable App-ID.
App-ID is the core technology that identifies applications regardless of port, using signatures, protocol decoders, and behavioral analysis. When an application uses non-standard ports, App-ID must be enabled to inspect traffic beyond simple port-based classification, ensuring accurate identification even if the application is not using its default port.
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.
✗
Define a custom service for the port.
Why it's wrong here
Custom services are for port mapping, not application identification.
✓
Enable App-ID.
Why this is correct
App-ID must be enabled to perform application identification.
Related concept
Read the scenario before looking for a memorised answer.
✗
Use a Content-ID profile.
Why it's wrong here
Content-ID profiles enforce security, not identification.
✓
Create a custom application signature.
Why this is correct
A custom signature allows the firewall to identify the application on the non-standard port.
Related concept
Read the scenario before looking for a memorised answer.
✗
Disable SSL Decryption.
Why it's wrong here
Disabling SSL decryption would make it harder to identify encrypted applications.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often think defining a custom service for the port is sufficient for identification, but App-ID requires either its built-in signatures or a custom application signature to accurately identify applications on non-standard ports.
Detailed technical explanation
How to think about this question
App-ID uses multiple mechanisms including protocol decoders (e.g., for HTTP, SSL, DNS), application signatures (byte patterns, transaction behaviors), and heuristic analysis to identify applications even when they run on non-standard ports. For example, if an application like Facebook uses port 8080 instead of 443, App-ID can still identify it by inspecting the SSL handshake or HTTP headers, whereas a custom service would only match port 8080 without identifying the application. Creating a custom application signature (Option D) is necessary when App-ID's built-in signatures fail to identify a custom or obfuscated application on a non-standard port, as it provides a tailored pattern for detection.
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 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.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
App-ID and Content-ID — This question tests App-ID and Content-ID — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Enable App-ID. — App-ID is the core technology that identifies applications regardless of port, using signatures, protocol decoders, and behavioral analysis. When an application uses non-standard ports, App-ID must be enabled to inspect traffic beyond simple port-based classification, ensuring accurate identification even if the application is not using its default port.
What should I do if I get this PCNSA question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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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.
Question Discussion
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