The answer is to use the predefined 'FTP' service object and also allow a high port range (e.g., TCP/1024-65535) in the firewall policy. This is correct because FTP passive mode separates control on TCP/21 from data transfer, which uses a dynamically negotiated high port on the server; the FortiGate firewall must permit that entire ephemeral range for the data channel to establish successfully. On the Fortinet NSE 4 Network Security Professional exam, this question tests your understanding of how application-layer protocols interact with stateful inspection—a common trap is assuming the predefined 'FTP' service alone covers passive mode, when it typically only includes TCP/21 (and sometimes TCP/20 for active mode). Remember that passive mode data ports are server-chosen and unpredictable, so a broad high-port allowance is mandatory. Memory tip: "Passive means ports are passive—they hide in the high numbers, so let them all through."
NSE4 Firewall Policies and NAT Practice Question
This NSE4 practice question tests your understanding of firewall policies and nat. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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.
An administrator needs to allow FTP traffic from the internal network to a specific server on the internet. The FTP server uses passive mode. Which service object should be used in the firewall policy to ensure proper operation?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use the predefined 'FTP' service object and also allow a high port range (e.g., TCP/1024-65535)
FTP uses TCP/21 for control. Passive mode uses a range of high ports for data. A generic FTP service object may include TCP/21 and TCP/20 (active mode). For passive, a custom service with TCP/21 and the data port range is needed, but the question asks which service object to use. Typically, the predefined 'FTP' service includes TCP/21 only. Many deployments create a custom service for passive. However, the best answer is to use the FTP service and also allow the ephemeral port range.
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.
✗
Use a custom service object with TCP/21 and TCP/20
Use the predefined 'FTP' service object and also allow a high port range (e.g., TCP/1024-65535)
Why this is correct
Passive FTP requires control on TCP/21 and data on a random high port. Allowing high port range ensures data connections succeed.
Related concept
Read the scenario before looking for a memorised answer.
✗
Use the predefined 'FTP' service object
Why it's wrong here
Predefined FTP only includes TCP/21, not the dynamic data ports.
✗
Use the 'ALL' service object
Why it's wrong here
While this would work, it is too permissive and not a security best practice.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→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 NSE4 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 NSE4 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Firewall Policies and NAT — This question tests Firewall Policies and NAT — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use the predefined 'FTP' service object and also allow a high port range (e.g., TCP/1024-65535) — FTP uses TCP/21 for control. Passive mode uses a range of high ports for data. A generic FTP service object may include TCP/21 and TCP/20 (active mode). For passive, a custom service with TCP/21 and the data port range is needed, but the question asks which service object to use. Typically, the predefined 'FTP' service includes TCP/21 only. Many deployments create a custom service for passive. However, the best answer is to use the FTP service and also allow the ephemeral port range.
What should I do if I get this NSE4 question wrong?
Identify which NSE4 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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This NSE4 practice question is part of Courseiva's free Fortinet 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 NSE4 exam.
Question Discussion
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