Question 1hardmultiple choice
Read the full DNS explanation →Question 492 of 1,000
Quick Answer
The answer is that DNS filtering requires proxy-based inspection mode on the policy. This is because FortiOS processes DNS filtering through the proxy engine, which performs deep packet inspection and content analysis on DNS traffic; flow-based inspection, by contrast, uses pattern matching and cannot apply DNS filter profiles. On the Fortinet NSE 4 Network Security Professional NSE4 exam, this concept tests your understanding of the critical difference between flow-based and proxy-based inspection modes, often appearing as a trap where sessions show port 53 traffic passing but filtering fails. A common mistake is assuming any inspection mode works for DNS filtering, but the key is that proxy mode is mandatory for DNS filter profiles to function. Memory tip: “DNS needs proxy—flow won’t block the DNS show.”
NSE4 Security Profiles Practice Question
This NSE4 practice question tests your understanding of security profiles. 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.
An administrator runs the CLI command: 'diagnose sys session list | grep -i dns' and sees sessions with dst port 53. The administrator has configured a DNS filter profile on the firewall policy. However, DNS requests are not being filtered. What is the MOST likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"most likely"Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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
✓
DNS filtering requires proxy-based inspection mode on the policy
DNS filtering in FortiOS requires proxy-based inspection mode. If the policy is set to flow-based, DNS filtering will not work. The administrator should change the inspection mode to proxy.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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.
- →
Security Profiles — study guide chapter
Learn the concepts, then practise the questions
- →
Security Profiles practice questions
Targeted practice on this topic area only
- →
All NSE4 questions
1,000 questions across all exam domains
- →
Fortinet NSE 4 Network Security Professional NSE4 study guide
Full concept coverage aligned to exam objectives
- →
NSE4 practice test guide
How to use practice tests most effectively before exam day
Related practice questions
Related NSE4 practice-question pages
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
System and Network Administration practice questions
Practise NSE4 questions linked to System and Network Administration.
Firewall Policies and NAT practice questions
Practise NSE4 questions linked to Firewall Policies and NAT.
Authentication and VPN practice questions
Practise NSE4 questions linked to Authentication and VPN.
Security Profiles practice questions
Practise NSE4 questions linked to Security Profiles.
High Availability and Diagnostics practice questions
Practise NSE4 questions linked to High Availability and Diagnostics.
NSE4 fundamentals practice questions
Practise NSE4 questions linked to NSE4 fundamentals.
NSE4 scenario practice questions
Practise NSE4 questions linked to NSE4 scenario.
NSE4 troubleshooting practice questions
Practise NSE4 questions linked to NSE4 troubleshooting.
Practice this exam
Start a free NSE4 practice session
Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.
FAQ
Questions learners often ask
What does this NSE4 question test?
Security Profiles — This question tests Security Profiles — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: DNS filtering requires proxy-based inspection mode on the policy — DNS filtering in FortiOS requires proxy-based inspection mode. If the policy is set to flow-based, DNS filtering will not work. The administrator should change the inspection mode to proxy.
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.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Last reviewed: Jun 21, 2026
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
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.