As a learning exercise, I'm replacing our FreeBSD firewall with a Debian one. The machine is used to provide masquerading for several Windows, Linux and FreeBSD boxes on our cable modem.
With Debian, FTP doesn't work from behind a standard masquerading firewall. I've observed the problem with ipfw and ipchains both. What is different about the default handling of FTP, ICQ and similar clients, and what should I read up on to change this behavior? Under FreeBSD, these worked without any special handling.
