On 9/8/05, Pablo Alonso <m0n0mza at gmail dot com> wrote:
> 
> Firewall -> Rules
> 
> WAN interface
>   Proto Source Port Destination Port Description
>   TCP  any       any  200.XX.XX.XX 20 FTP
>   TCP  any       any  200.XX.XX.XX 21 FTP
> 
>   TCP  any       any  192.168.XX.XX   20 FTP
>     TCP  any       any  192.168.XX.XX   21 FTP
> 

20 is only the source port on FTP data connections, opening that port
as a destination port is unnecessary.

check this out: 
http://wiki.m0n0.ch/wikka.php?wakka=PseudoFTP

-Chris