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?
The session is a TCP session that has been established for 1 hour and will expire in about 1 hour
Correct interpretation.
The session is a UDP session with destination port 443
Why wrong: proto=6 is TCP, not UDP.
The session will expire in 3600 seconds
Why wrong: expire=3599, not 3600.
The session is a TCP session in SYN_SENT state
Why wrong: proto_state=01 indicates ESTABLISHED, not SYN_SENT.
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 a TCP session that has been established for 1 hour and will expire in about 1 hour
Option A is correct because the output shows `proto=6`, which indicates TCP (protocol number 6), and `proto_state=01` corresponds to TCP state ESTABLISHED. The `duration=3600` means the session has been active for 3600 seconds (1 hour), and `expire=3599` indicates the session will expire in 3599 seconds (approximately 1 hour). This matches the description of a TCP session established for 1 hour with about 1 hour remaining before expiry.
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 a TCP session that has been established for 1 hour and will expire in about 1 hour
Why this is correct
Correct interpretation.
Related concept
Read the scenario before looking for a memorised answer.
The session is a UDP session with destination port 443
The session will expire in 3600 seconds
Why it's wrong here
expire=3599, not 3600.
The session is a TCP session in SYN_SENT state
Why it's wrong here
proto_state=01 indicates ESTABLISHED, not SYN_SENT.
Common exam traps
The trap here is that candidates often confuse `duration` with `expire` or misinterpret `proto=6` as generic 'TCP' without recognizing that `proto_state=01` specifically indicates the ESTABLISHED state, not SYN_SENT or other states.
Detailed technical explanation
In FortiOS, the `diagnose sys session filter` command displays session table entries with protocol numbers from IANA assignments (TCP=6, UDP=17). The `proto_state` field uses a Fortinet-specific encoding where 01 means TCP ESTABLISHED, 02 means SYN_SENT, and 03 means SYN_RECV. The `expire` timer decrements from the session timeout value (default 3600 seconds for TCP established sessions) and when it reaches 0, the session is removed. This is critical for troubleshooting asymmetric routing or firewall session timeouts in real-world deployments.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
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FAQ
Firewall Policies and NAT — This question tests Firewall Policies and NAT — Read the scenario before looking for a memorised answer..
The correct answer is: The session is a TCP session that has been established for 1 hour and will expire in about 1 hour — Option A is correct because the output shows `proto=6`, which indicates TCP (protocol number 6), and `proto_state=01` corresponds to TCP state ESTABLISHED. The `duration=3600` means the session has been active for 3600 seconds (1 hour), and `expire=3599` indicates the session will expire in 3599 seconds (approximately 1 hour). This matches the description of a TCP session established for 1 hour with about 1 hour remaining before expiry.
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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