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Re: masquerading & ftp



On Tue, Feb 15, 2000 at 03:06:00PM -0600, Brian McGroarty wrote:
: 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.

You need to use passive ftp from behind a masquerading box. 

I thought there was a masq module for FTP, but I guess I was thinking of
the Cisco PIX.  You have to examine each packet in a non-passive FTP
session and rewrite IPs when NAT or masq is in play.

-- 
Nathan Norman                    Network Magician, Eclectic Engineer
GPG Key ID 1024D/51F98BB7                       "Eschew Obfuscation"
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