The correct answer is to create a security rule with the application 'ftp' and enable 'FTP Alg' in the Application Override settings. This configuration is required because FTP traffic inspection relies on the firewall understanding the separate control channel on TCP 21 and the dynamically negotiated data channel; enabling FTP Alg allows the Palo Alto Networks firewall to inspect FTP commands, dynamically open pinholes for the data channel, and maintain stateful handling for both active and passive modes. On the PCNSA exam, this question tests your understanding of how application-level gateways solve the challenge of inspecting multi-channel protocols—a common trap is assuming a simple port-based rule for TCP 21 will suffice, but without FTP Alg, the data channel traffic will be blocked or bypass inspection. A useful memory tip is to think of FTP Alg as the firewall’s “translator” that reads the FTP conversation to know exactly which port to open for data, ensuring no packet is left uninspected.
PCNSA Core Concepts Practice Question
This PCNSA practice question tests your understanding of core concepts. 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.
A network administrator wants to allow FTP traffic from the internal network (zone: trust) to an external server (zone: untrust) while ensuring that the firewall can inspect the FTP control and data channels. Which security rule configuration is required?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Create a rule with application 'ftp' and enable 'FTP Alg' in the Application Override settings
Option C is correct because FTP uses separate control (TCP 21) and data channels, and the firewall must inspect both to enforce security policies. Enabling 'FTP Alg' in the Application Override settings allows the Palo Alto Networks firewall to dynamically open pinholes for the data channel and perform deep inspection of FTP commands, ensuring proper stateful handling of active and passive modes.
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.
✗
Create a rule with service 'tcp-21' and application 'any'
Why it's wrong here
This only allows control channel; data channel on random ports may be blocked.
✗
Create a rule with application 'ftp' and disable Application Override
Why it's wrong here
Without Application Override, the firewall may not properly associate data channels.
✓
Create a rule with application 'ftp' and enable 'FTP Alg' in the Application Override settings
Why this is correct
FTP ALG ensures the firewall can inspect FTP control and negotiate data channel inspection.
Related concept
Read the scenario before looking for a memorised answer.
✗
Create a rule with application 'ftp' and service 'application-default'
Why it's wrong here
Application 'ftp' does not inherently handle dynamic data channel inspection without ALG support.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume simply setting the application to 'ftp' is sufficient, but they overlook the need to explicitly enable FTP Alg to handle the dynamic data channel negotiation required for full inspection.
Detailed technical explanation
How to think about this question
FTP ALG (Application Layer Gateway) is essential for stateful inspection of FTP because the protocol negotiates ephemeral data ports via PORT or PASV commands. The Palo Alto Networks firewall's FTP ALG intercepts these commands, dynamically creates security policies for the negotiated data channel, and ensures that both control and data flows are inspected, preventing bypass attacks. In real-world scenarios, without FTP ALG, passive FTP transfers may fail because the firewall blocks the random high ports used for data.
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 PCNSA 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.
Core Concepts — This question tests Core Concepts — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Create a rule with application 'ftp' and enable 'FTP Alg' in the Application Override settings — Option C is correct because FTP uses separate control (TCP 21) and data channels, and the firewall must inspect both to enforce security policies. Enabling 'FTP Alg' in the Application Override settings allows the Palo Alto Networks firewall to dynamically open pinholes for the data channel and perform deep inspection of FTP commands, ensuring proper stateful handling of active and passive modes.
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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Question Discussion
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