F-SECURE INTERNET GATEKEEPER FOR LINUX 4.01 Administrator's Manual page 143

Transparent mode (Router or Bridge), Active FTP
Client (0.0.0.3)
TCP connect(to: 0.0.0.2:21)
----------------------------->
220
<-----------------------------
USER user
----------------------------->
331 Password required
<-----------------------------
PASS password
----------------------------->
230 User logged in.
<-----------------------------
PORT 0,0,0,3,0,3
----------------------------->
200 PORT command successful.
<-----------------------------
RETR /file
----------------------------->
TCP connect
(From: 0.0.0.1:20 To: 0.0.0.3:3)
<=====================
150 Opening data connection.
<-----------------------------
Internet Gatekeeper (fsigk,0.0.0.1)
ftpserver
(the rest is processed in the same way as in proxy mode)
F-Secure Internet Gatekeeper for Linux/Administrator's Guide
FTP server (ftpserver, 0.0.0.2)
TCP connect(to: 0.0.0.2:21)
----------------------------->
220 ftpserver
<-----------------------------
USER user
----------------------------->
331 Password required
<-----------------------------
PASS password
----------------------------->
230 User logged in.
<-----------------------------
PORT 0,0,0,1,0,1
----------------------------->
200 PORT command successful.
<-----------------------------
RETR /file
----------------------------->
TCP connect
(From: 0.0.0.2:20 To: 0.0.0.1:1)
<=====================
150 Opening data connection.
<-----------------------------
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