PCNSE Securing Traffic and App-ID Practice Question
A security administrator is troubleshooting App-ID on a firewall that is deployed in a Layer 2 transparent mode. The administrator notices that some applications are not being identified correctly, even though the traffic is not encrypted. What is the most likely reason for this issue?
⚠ Common exam trap
The trap here is assuming that Layer 2 mode inherently prevents App-ID inspection, when in fact it is supported, but configuration can disable it.
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 firewall may be configured to bypass App-ID inspection for certain zones or interfaces.
In Layer 2 transparent mode, the firewall can inspect traffic, but App-ID may be bypassed if certain zones or interfaces are configured to disable inspection. This can happen if the administrator has set the zone to not perform App-ID or if the traffic is excluded from inspection. Checking these configurations is the most likely solution.
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 requires the firewall to be in Layer 3 mode to perform protocol decoding.
Why it's wrong here
App-ID does not require Layer 3 mode; it works in Layer 2 transparent mode as well. Protocol decoding is performed on the traffic regardless of the mode. The misconception that Layer 3 is required is incorrect. The issue is more likely due to configuration settings that disable inspection on specific interfaces or zones.
- ✗
Layer 2 transparent mode does not support App-ID inspection.
Why it's wrong here
Layer 2 transparent mode does support App-ID inspection. The firewall can inspect traffic as it passes through, regardless of whether it is in Layer 2 or Layer 3 mode. The issue is not inherent to the mode itself, but rather to configuration or other factors that affect App-ID's ability to see the traffic.
- ✗
The firewall is not in the path of the traffic, so it cannot inspect it.
Why it's wrong here
In Layer 2 transparent mode, the firewall is in the path of the traffic and can inspect it. If the firewall were not in the path, it would not see the traffic at all. The scenario states that the administrator notices some applications are not identified, implying the firewall is seeing the traffic but not identifying it correctly.
- ✓
The firewall may be configured to bypass App-ID inspection for certain zones or interfaces.
Why this is correct
In Layer 2 transparent mode, the firewall can be configured with zones and interfaces that have App-ID inspection disabled or bypassed, such as when using a 'tap' mode or when certain traffic is excluded. This can prevent App-ID from identifying applications. The administrator should check the zone and interface configurations to ensure App-ID is enabled.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Palo Alto Networks exam blueprint
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.