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SonicOS Enhanced 4.0 Administrator Guide
Packet Capture
The Packet Capture tool tracks the status of a communications stream as it moves from source
to destination. This is a useful tool to determine if a communications stream is being stopped
at the SonicWALL security appliance, or is lost on the Internet.
To interpret this tool, it is necessary to understand the three-way handshake that occurs for
every TCP connection. The following displays a typical three-way handshake initiated by a host
on the SonicWALL security appliance LAN to a remote host on the WAN.
Step 1 TCP received on LAN [SYN]
From 192.168.168.158 / 1282 (00:a0:4b:05:96:4a)
To 204.71.200.74 / 80 (02:00:cf:58:d3:6a)
The SonicWALL security appliance receives SYN from LAN client.
Step 2 TCP sent on WAN [SYN]
From 207.88.211.116 / 1937 (00:40:10:0c:01:4e)
To 204.71.200.74 / 80 (02:00:cf:58:d3:6a)
The SonicWALL security appliance forwards SYN from LAN client to remote host.
Step 3 TCP received on WAN [SYN,ACK]
From 204.71.200.74 / 80 (02:00:cf:58:d3:6a)
To 207.88.211.116 / 1937 (00:40:10:0c:01:4e)
The SonicWALL security appliance receives SYN,ACK from remote host.
Step 4 TCP sent on LAN [SYN,ACK]
From 204.71.200.74 / 80 (02:00:cf:58:d3:6a)
To 192.168.168.158 / 1282 (00:a0:4b:05:96:4a)
The SonicWALL security appliance forwards SYN,ACK to LAN client.
Step 5 TCP received on LAN [ACK]
From 192.168.168.158 / 1282 (00:a0:4b:05:96:4a)
To 204.71.200.74 / 80 (02:00:cf:58:d3:6a)