PCNSE Securing Traffic and App-ID Practice Question
This PCNSE practice question tests your understanding of securing traffic and app-id. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
Exhibit
Refer to the exhibit.
admin@PA-220> show system info | match appid
appid version: 8000-7120
appid last update: 2024/10/01 03:00:00
appid packet buffer: 1024 KB
appid max sessions: 500000
Refer to the exhibit. A firewall administrator is troubleshooting why some applications are not being correctly identified. The firewall is running App-ID version 8000-7120. What does the 'appid packet buffer: 1024 KB' indicate?
Exhibit
Refer to the exhibit.
admin@PA-220> show system info | match appid
appid version: 8000-7120
appid last update: 2024/10/01 03:00:00
appid packet buffer: 1024 KB
appid max sessions: 500000
A
App-ID can only handle 1024 KB of packet data per session.
Why wrong: The buffer is shared, not per session.
B
The firewall can buffer up to 1024 KB of packet data for App-ID analysis.
This buffer stores packets for deep inspection when needed.
C
The firewall logs the first 1024 KB of every session for App-ID.
Why wrong: The buffer is for analysis, not logging.
D
The firewall offloads App-ID processing to a dedicated buffer of 1024 KB.
Why wrong: There is no offloading; the buffer is on the firewall.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The firewall can buffer up to 1024 KB of packet data for App-ID analysis.
The 'appid packet buffer: 1024 KB' indicates the maximum amount of packet payload data the firewall can buffer per session for App-ID analysis. This buffer stores the initial packets of a session so that App-ID can inspect the payload for application signatures, even if the data arrives in multiple packets. Option B correctly states this buffering capability.
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.
✗
App-ID can only handle 1024 KB of packet data per session.
Why it's wrong here
The buffer is shared, not per session.
✓
The firewall can buffer up to 1024 KB of packet data for App-ID analysis.
Why this is correct
This buffer stores packets for deep inspection when needed.
Related concept
Read the scenario before looking for a memorised answer.
✗
The firewall logs the first 1024 KB of every session for App-ID.
Why it's wrong here
The buffer is for analysis, not logging.
✗
The firewall offloads App-ID processing to a dedicated buffer of 1024 KB.
Why it's wrong here
There is no offloading; the buffer is on the firewall.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is confusing the buffer size with a per-session data limit or a logging threshold, when in fact it is a temporary storage mechanism for App-ID analysis.
Detailed technical explanation
How to think about this question
Under the hood, the appid packet buffer stores the initial bytes of a session (up to the configured size) to allow App-ID to perform deep packet inspection (DPI) on the application payload, even if the application data is spread across multiple TCP segments. This is critical for identifying applications that use dynamic ports or are encapsulated within other protocols (e.g., SSL, HTTP/2). In real-world scenarios, if the buffer is too small, App-ID may fail to identify applications that require more payload data for signature matching, leading to misclassification or 'unknown' traffic.
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 — 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 firewall can buffer up to 1024 KB of packet data for App-ID analysis. — The 'appid packet buffer: 1024 KB' indicates the maximum amount of packet payload data the firewall can buffer per session for App-ID analysis. This buffer stores the initial packets of a session so that App-ID can inspect the payload for application signatures, even if the data arrives in multiple packets. Option B correctly states this buffering capability.
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.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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