This NSE4 practice question tests your understanding of firewall policies and nat. 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 'diagnose sys session filter dport 443' and see the following output:
proto=6 proto_state=01 duration=3600 expire=3599
What does this indicate about the session?
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 in the SYN_SENT state, waiting for a SYN-ACK
The output shows `proto=6` (TCP) and `proto_state=01`, which in Fortinet's session table corresponds to the TCP state `SYN_SENT` (the session has sent a SYN and is awaiting a SYN-ACK). The `duration=3600` and `expire=3599` indicate the session has been alive for 3600 seconds and will expire in 3599 seconds, but the state itself is not established or closing. Option A is correct because `proto_state=01` specifically maps to the TCP SYN_SENT state in FortiOS session diagnostics.
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 session is in the SYN_SENT state, waiting for a SYN-ACK
Why this is correct
proto_state=01 corresponds to TCP SYN_SENT (bit 0 set).
Related concept
Read the scenario before looking for a memorised answer.
The session is fully established and actively transferring data
Why it's wrong here
Established state typically has proto_state=02 or 10 (depending on representation).
✗
The session is being torn down and will expire soon
Why it's wrong here
Tear-down states have different proto_state values (e.g., FIN_WAIT).
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates see `duration=3600` and `expire=3599` and mistakenly assume the session is 'about to expire' (option D), when in fact the expire value is still large and the session is in an early handshake state, not a teardown state.
Detailed technical explanation
How to think about this question
In FortiOS, the `proto_state` field uses hexadecimal values derived from the Linux TCP state machine: `01` is TCP_SYN_SENT, `02` is TCP_SYN_RECV, `06` is TCP_ESTABLISHED, and `0B`/`0C` are FIN_WAIT1/TIME_WAIT. The `diagnose sys session filter` command is critical for troubleshooting incomplete TCP handshakes, such as when a client sends a SYN but the server is unreachable or a firewall rule blocks the SYN-ACK. In real-world scenarios, a high number of sessions stuck in `proto_state=01` often indicates a network path issue or a misconfigured load balancer.
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 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 exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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: The session is in the SYN_SENT state, waiting for a SYN-ACK — The output shows `proto=6` (TCP) and `proto_state=01`, which in Fortinet's session table corresponds to the TCP state `SYN_SENT` (the session has sent a SYN and is awaiting a SYN-ACK). The `duration=3600` and `expire=3599` indicate the session has been alive for 3600 seconds and will expire in 3599 seconds, but the state itself is not established or closing. Option A is correct because `proto_state=01` specifically maps to the TCP SYN_SENT state in FortiOS session diagnostics.
What should I do if I get this NSE4 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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