NSE4 System and Network Administration Practice Question
An admin runs 'diagnose sys session filter dport 443' and sees the following output: proto=6 proto_state=01 duration=3600 expire=3599 What does this indicate?
⚠ Common exam trap
The trap here is that candidates may misinterpret `proto_state=01` as a half-open connection (like SYN_SENT) because they confuse the numeric state value with TCP flags, when in fact 01 specifically means ESTABLISHED in FortiGate's session table.
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 an established TCP session for HTTPS traffic
The output shows `proto=6` (TCP), `proto_state=01` (TCP established), `dport=443` (HTTPS), and a duration/expire indicating an active session. This confirms an established TCP session for HTTPS traffic, making D correct.
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 a half-open TCP connection
Why it's wrong here
A half-open TCP connection indicates a SYN has been received but the three-way handshake is incomplete; in FortiGate's session table, this typically appears with a proto_state value of 00 or similar (e.g., SYN_SENT), not proto_state=01. The filter output shows proto=6 and proto_state=01, which directly signifies a fully established session, and dport 443 is the HTTPS port, not a sign of a half-open state. Additionally, half-open conditions are usually transient and would not be the default interpretation for a normal 443 TCP session.
- ✗
The session is a multicast session
Why it's wrong here
Multicast traffic uses UDP or raw IP protocols, never TCP, and the session table output explicitly shows proto=6, which is the IP protocol number for TCP. Furthermore, multicast destinations are in the 224.0.0.0/4 range, while this session's destination port 443 indicates unicast HTTPS traffic to a specific server. FortiGate session filters for dport 443 would not capture multicast sessions, and multicast does not maintain TCP proto_state values like the established state shown in the output.
- ✗
The session is a UDP session for DNS over HTTPS
Why it's wrong here
DNS over HTTPS (DoH) is specifically HTTP/2 or HTTP/3 over TLS, which runs on TCP (or QUIC for HTTP/3, but still not plain UDP on port 443); it is not a UDP-based DNS query. The session output shows proto=6, and UDP is proto=17, so this cannot be a UDP session. Moreover, DoH uses port 443 as a TCP destination port, and the proto_state=01 field is a TCP state indicator, not something UDP sessions would have.
- ✓
The session is an established TCP session for HTTPS traffic
Why this is correct
The session is an established TCP session because the output field proto=6 specifies TCP (protocol 6), and proto_state=01 corresponds to the TCP established state, meaning the three-way handshake completed successfully. The destination port 443 is the well-known port for HTTPS, so this session represents active HTTPS traffic traversing the FortiGate. When combined, these values unambiguously identify a normal, established TCP connection for HTTPS, ruling out half-open, multicast, or UDP alternatives.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This NSE4 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 NSE4 exam.