The answer is that these sessions are in the SYN_SENT state and have not completed the three-way handshake. This is correct because proto=6 identifies the traffic as TCP, and the proto_state=01 value specifically indicates the SYN_SENT state, meaning the client has sent a SYN but the server has not yet responded with a SYN-ACK. The long duration of 3600 seconds with nearly full expiration suggests these are half-open sessions that never completed the handshake, which is a classic indicator of a SYN flood attack. On the Fortinet NSE 4 exam, this question tests your ability to interpret the diagnose sys session filter dport 443 output to identify abnormal TCP session states, a key skill for troubleshooting and security analysis. A common trap is confusing proto_state=01 with an established connection, but remember that state 01 is the initial SYN sent, not the completed handshake. For a quick memory tip: think of "01" as "one-way started" — the SYN went out, but nothing came back.
NSE4 Security Profiles Practice Question
This NSE4 practice question tests your understanding of security profiles. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. 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.
You run the following CLI command on a FortiGate:
diagnose sys session filter dport 443
diagnose sys session list
The output shows many sessions with 'proto=6 proto_state=01 duration=3600 expire=3599'. What does this indicate about the traffic?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The sessions are in the SYN_SENT state and have not completed the three-way handshake
Option B is correct. The proto=6 indicates TCP, and proto_state=01 indicates a TCP session in the SYN_SENT state (i.e., the three-way handshake is not complete). The long duration suggests these are half-open sessions, possibly indicating a SYN flood attack.
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.
✗
The sessions are fully established and idle
Why it's wrong here
A fully established TCP session would show proto_state=02 (ESTABLISHED). Proto_state=01 is SYN_SENT.
The sessions are being inspected by SSL deep inspection
Why it's wrong here
The session list does not provide SSL inspection status; this is a TCP state issue.
✓
The sessions are in the SYN_SENT state and have not completed the three-way handshake
Why this is correct
Correct as explained.
Related concept
Read the scenario before looking for a memorised answer.
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.
Trap categories for this question
Command / output trap
A fully established TCP session would show proto_state=02 (ESTABLISHED). Proto_state=01 is SYN_SENT.
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 — 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: The sessions are in the SYN_SENT state and have not completed the three-way handshake — Option B is correct. The proto=6 indicates TCP, and proto_state=01 indicates a TCP session in the SYN_SENT state (i.e., the three-way handshake is not complete). The long duration suggests these are half-open sessions, possibly indicating a SYN flood attack.
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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