We use a linux server as a firewall and forward packets to different servers. In this case, we applied the iptables to forward packets from $Fido to $AtlasFtp for FTP. It is ok that we can log in the ftp server, but unable to do other things such as "ls", neither does Windows GUI FTP. Does anyone know why the FTP does not work? (we opened the port 20 and 21 for FTP)? Is there something wrong with ports? ############ FTP ######### iptables -t nat -A PREROUTING -i eth0 --dst $Fido -p tcp --dport $FTP_Port -j DNAT --to $AtlasFtp # iptables -t nat -A PREROUTING -i eth0 --dst $Fido -p udp --dport $FTP_Port -j DNAT --to $AtlasFtp iptables -t nat -A POSTROUTING -p tcp --dst $AtlasFtp --dport $FTP_Port -j SNAT --to-source $Fido # iptables -t nat -A POSTROUTING -p tcp --dst $AtlasFtp --dport $FTP_Port -j SNAT --to-source $Fido iptables -t nat -A OUTPUT --dst $Fido -p tcp --dport $FTP_Port -j DNAT --to-destination $AtlasFtp # iptables -t nat -A OUTPUT --dst $Fido -p udp --dport $FTP_Port -j DNAT --to-destination $AtlasFtp Yan