Ftp behind firewall/nat

Erik Norgaard norgaard at locolomo.org
Tue Feb 1 01:16:56 PST 2005

eric wyzerski wrote:
> My setup work wells with Active ftp but not with passive ftp. Your setup 
> doestnt work with passive ftp. From ipfilter faq:
> # I have an FTP server behind an IPF firewall, and I'm having problems 
> serving passive FTP.

Sorry, from your original post it was not clear to me if your problem 
was ftp-client behind nat or ftp-server behind nat. The solution I gave 
solve the ftp-client behind nat problem, both active and passive ftp.

The IPF howto also notes that setting up an ftp server behind a NAT is a 
mess and one should _not_ try to reverse the setup for ftp-client behind 
nat. I don't have the solution for server behind nat.

> passive ports 32768 49151
>    passive address your.pub.IP.addr

I don't know what is standard or if there is one, but IANA has assigned 
ports > 49151 for dynamic port allocation, which seems to suggest that 
the ports chosen should be in that interval.

Cheers, Erik

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