This NSE4 practice question tests your understanding of firewall policies and nat. 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.
An administrator uses 'diagnose sys session list' and sees the following output for a session: 'proto=6 proto_state=01 duration=3600 expire=3599'. The session is for HTTPS traffic. What does 'proto_state=01' typically indicate in FortiGate?
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 initial connection setup phase (SYN_SENT)
In FortiGate, 'proto_state=01' for TCP (proto=6) indicates the session is in the SYN_SENT phase, meaning the initial SYN packet has been sent but the three-way handshake is not yet complete. For HTTPS traffic, this shows the session is still in the connection setup stage, not fully established. The 'duration' and 'expire' values reflect the time since the session was created and the remaining timeout, which is typical for an incomplete handshake.
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.
An established TCP session typically shows proto_state=0x1e (30) or similar, not 01.
✓
The session is in the initial connection setup phase (SYN_SENT)
Why this is correct
proto_state=01 indicates the TCP handshake is in progress or incomplete, suggesting the session is not fully established.
Related concept
Read the scenario before looking for a memorised answer.
✗
The session is being inspected by a security profile
Why it's wrong here
Security profile inspection does not change proto_state to 01; it remains as per TCP state.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse 'proto_state=01' with a fully established session because they see 'duration' and 'expire' values and assume the session is active, but the state code explicitly indicates the handshake is incomplete.
Trap categories for this question
Similar concept trap
An established TCP session typically shows proto_state=0x1e (30) or similar, not 01.
Command / output trap
An established TCP session typically shows proto_state=0x1e (30) or similar, not 01.
Detailed technical explanation
How to think about this question
FortiGate uses internal TCP state codes derived from the Linux kernel's TCP state machine: '01' corresponds to TCP_SYN_SENT, '02' to TCP_ESTABLISHED, and '03' to TCP_FIN_WAIT1, etc. In real-world scenarios, a session stuck in 'proto_state=01' for an extended duration may indicate a SYN flood attack or a misconfigured client/server, as the three-way handshake never completes, causing the session to eventually timeout after the default 10-second SYN timeout.
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 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
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 initial connection setup phase (SYN_SENT) — In FortiGate, 'proto_state=01' for TCP (proto=6) indicates the session is in the SYN_SENT phase, meaning the initial SYN packet has been sent but the three-way handshake is not yet complete. For HTTPS traffic, this shows the session is still in the connection setup stage, not fully established. The 'duration' and 'expire' values reflect the time since the session was created and the remaining timeout, which is typical for an incomplete handshake.
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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