Active mode FTP over PPP



Hi. I wonder if somebody could shed some light on a problem I'm having
with "Active mode" FTP over a serial PPP link.

First some background:

I'm running a SuSE Enterprise 9 server (Server "A") with pppd version
2.4.2 installed along with Mgetty v1.1.30-288 and pure-ftp v1.0.18.
There is no firewall running.

I have three servers, which I'll call A (as mentioned above), B & C.
All have an ethernet interface each and are on the same subnet.

Server "A" has a number of modems installed all of which work just
fine and can handle local (i.e just to itself and not involving "B" or
"C") active and passive modes of FTP over the PPP link that get
established from the calling Linux or Windows clients.

All machines can see each other and I can FTP using active and passive
modes between all three over the ethernet connections with no problems
whatsover.

I can do "passive" mode Ftp's from my "client" over the Dial-Up PPP
interfaces on server "A" to server "A", "B" and "C" just fine.

The problem:
Arises when "client" dials the PPP link to machine "A" it can't do an
"active mode" FTP to machines "B" or "C" it just bombs with errors
listed in the output below . I can do an "active mode" Ftp from
"client" to machine "A" without any problem. Both "B" and "C" are
using different FTP servers. One using PureFTP the other WU Ftp just
incase you're wondering why the diffrent error messages from each
server.

It smells like a problem with PPP but why would PPP be causing this
problem - why should it care about active or passive FTP's - this is
driving me nuts, any ideas would be gratefully received.

Please see error output below. I'll be happy to supply any more info
should anybody require it.

thanks, chris


Error message generated when trying to "ls" on connection to Server
"B" :-

500 Illegal PORT rejected (address wrong).
425 Can't build data connection: Connection refused.
ftp> ls
425 Can't build data connection: Connection refused.
ftp>


Error message generated when trying to "ls" on connection to Server
"C" :-

200-FXP transfer: from 192.168.100.26 to 192.168.150.8
200 PORT command successful
425 Could not open data connection to port 3720: Connection timed out
ftp>

.