Interpreting FortiGate Session Output: Proto_State 01 Indicates TCP SYN_SENT Waiting for SYN-ACK
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?
Quick Answer
The answer is that proto_state=01 indicates the session is in TCP SYN_SENT, waiting for a SYN-ACK. This is correct because in FortiGate’s session table, proto=6 confirms TCP, and the proto_state field uses a numeric code where 01 specifically represents the SYN_SENT phase of the three-way handshake. The duration of 3600 seconds and expire of 3599 show the session has been waiting nearly a full hour, meaning the firewall forwarded the initial SYN but never received the expected SYN-ACK from the remote host, so the session remains unestablished. On the Fortinet NSE 7 Advanced Security NSE7 exam, this question tests your ability to read raw session output and correlate proto_state values with TCP state machine transitions—a common trap is confusing proto_state=01 with an established session (which would show 02 for ESTABLISHED). Remember the memory tip: “01 is the one that’s sent, waiting for a response.”
⚠ Common exam trap
The trap here is that candidates often misinterpret `proto_state=01` as an established session because they associate '01' with a binary 'on' or 'active' state, but in Fortinet's TCP state encoding, 01 specifically means SYN_SENT, not established.
Answer choices
Why each option matters
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 SYN_SENT state, waiting for SYN-ACK
The output shows `proto=6` (TCP), `proto_state=01`, `duration=3600`, and `expire=3599`. In Fortinet's session table, `proto_state=01` for TCP indicates the session is in the SYN_SENT state, meaning the firewall has forwarded a SYN packet and is waiting for a SYN-ACK from the remote host. The session is not yet established, as the three-way handshake has not completed.
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 timed out
Why it's wrong here
expire=3599 means it's still active.
- ✗
The session is closing (FIN_WAIT)
Why it's wrong here
FIN_WAIT states have different codes.
- ✓
The session is in SYN_SENT state, waiting for SYN-ACK
Why this is correct
proto_state=01 indicates SYN_SENT.
- ✗
The session is fully established (proto_state=01 means established)
Why it's wrong here
01 is SYN_SENT, not established.
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Variation 1. 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?
hard- A.The session is in SYN_SENT state and cannot be established
- ✓ B.The session is an established TCP session with about one hour remaining before timeout
- C.The session is a UDP session using port 443
- D.The session has a duration of 3600 seconds and will expire immediately
Why B: The output shows a TCP session (proto=6) with state 01, which in Fortinet's session table indicates an established TCP connection. The duration of 3600 seconds and expire value of 3599 seconds mean the session has been active for about one hour and has approximately one hour remaining before the idle timeout expires. This matches option B.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This NSE7 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 NSE7 exam.