Quick Answer
The correct interpretation is that the session is about to expire in 3599 seconds, as indicated by the expire field in the output of the diagnose sys session filter dport 443 command. This field shows the remaining time before the session is removed from the FortiGate session table, while the duration field of 3600 seconds reveals how long the session has already been active, meaning the total session lifetime is 7200 seconds. On the Fortinet NSE 4 Network Security Professional exam, this question tests your ability to read and interpret session table diagnostics, a common skill for troubleshooting firewall behavior. A frequent trap is confusing duration with expire or assuming the session is idle or in error; here, proto=6 confirms a normal TCP session, and proto_state=01 indicates SYN_SENT, not a problem. Remember the memory tip: “Duration is the past, expire is the future—add them for the total lifetime.”
This NSE4 practice question tests your understanding of system and network administration. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 'diagnose sys session filter dport 443' and see the following output: proto=6 proto_state=01 duration=3600 expire=3599 What does this indicate?
The session is in an error state
Why wrong: proto_state=01 is TCP SYN_SENT, not an error.
The session has been idle for 3600 seconds
Why wrong: duration=3600 is the total session time, not idle time.
The session is to port 3600
Why wrong: dport 443 filtered the output, not port 3600.
The session is about to expire in 3599 seconds
expire=3599 shows remaining session lifetime.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
The session is about to expire in 3599 seconds
The 'expire=3599' field indicates the session will be removed from the session table in 3599 seconds. The 'duration=3600' shows the session has been active for 3600 seconds, so the total session lifetime is 7200 seconds (3600 + 3599). This is a normal TCP session (proto=6) in state 01 (SYN_SENT), not an error or idle condition.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
The session is in an error state
Why it's wrong here
proto_state=01 is TCP SYN_SENT, not an error.
The session has been idle for 3600 seconds
Why it's wrong here
duration=3600 is the total session time, not idle time.
The session is to port 3600
Why it's wrong here
dport 443 filtered the output, not port 3600.
The session is about to expire in 3599 seconds
Why this is correct
expire=3599 shows remaining session lifetime.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
The trap here is confusing 'duration' (time since session started) with 'expire' (time until session ends), leading candidates to incorrectly interpret the 3600 value as idle time or a port number.
Trap categories for this question
Command / output trap
dport 443 filtered the output, not port 3600.
Detailed technical explanation
The 'diagnose sys session filter' command in FortiOS displays session table entries. The 'expire' field is a countdown timer that decrements from the session's configured timeout value; when it reaches 0, the session is purged. In this output, the session has been alive for 3600 seconds (duration) and will expire in 3599 seconds, meaning the total timeout is 7200 seconds—typical for a long-lived TCP connection like HTTPS. The 'proto_state=01' corresponds to TCP state 1 (SYN_SENT), which is the initial handshake state, indicating the session is still being established.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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
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FAQ
System and Network Administration — This question tests System and Network Administration — Read the scenario before looking for a memorised answer..
The correct answer is: The session is about to expire in 3599 seconds — The 'expire=3599' field indicates the session will be removed from the session table in 3599 seconds. The 'duration=3600' shows the session has been active for 3600 seconds, so the total session lifetime is 7200 seconds (3600 + 3599). This is a normal TCP session (proto=6) in state 01 (SYN_SENT), not an error or idle condition.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
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