ftp problem LAN behind NAT/fierwall to LAN

ftp problem LAN behind NAT/fierwall to LAN

Post by vlad » Sun, 07 Mar 2004 23:28:19

hi I have a problem with ftp connecion
there is a ftp server on port 2121(forward on LAN)
and me also on LAN but another one.
I asked my adminnistrator to free this port so i could conect to this
ftp , and so he did, i can connect to it but when mz ftp client trah to
list files i get
350 Restarting at 100. Send STORE or RETRIEVE.
350 Restarting at 0. Send STORE or RETRIEVE.
257 "/" is current directory.
200 Type set to A.
227 Entering Passive Mode (xxx,x,xx,xx,13,230)
Data Socket Error: Network is unreachable
List Error

1. Port forwarding, NAT and LAN-to-LAN connections

Hello all,

Here's a stumper. I'm using Debian 2.2 and ipchains to set up a bunch
of services running on a LAN with only one external host doing
port-by-port forwarding to the hosts on the LAN. So,
External IP  forwarded to -->
External IP forwarded to -->

With a couple of simple statements to ipmasqadm:
ipmasqadm portfw -f
ipmasqadm portfw -a -P tcp -L 80 -R 80
ipmasqadm portfw -a -P tcp -L 25 -R 25

this works like a charm in all cases but one-- when the connection is
initiated from a host inside of the LAN. So, if host
tries to connect to, nothing happens. tcpdump shows
that packets are flying about, but the connection is never officially

I suspect that this has to do with the way that MASQ works in linux,
but I am not sure. I have scoured this list and it seems that the only
thing that comes close in posting is this post:

but there was never an acceptable resolution. Using DNS to
short-circuit the firewall's NAT seems kludgey.

Any help would be greatly appreciated.


PS the rest of my rules are set as promiscous as possible for the
purposes of solving this problem:

ipchains -F
ipchains -P input ACCEPT
ipchains -P output ACCEPT
ipchains -P forward ACCEPT
ipchains -P forward -s -j MASQ

and everything else (NAT, forwarding from an external address) is
working jsut fine.

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