[oclug] Linux Port-forwarding problem.

[Peter Rofner]

I'm working on integrating some Linux systems with Windows NT/2000 based
systems. I'm having a really odd problem I was hoping somebody could help me
with.

I've got a Rebel.com NetWinder running as a firewall/gateway (Linux on a
StrongARM processor - nothing special). It's acting as a web host as well as
port forwarding port 25 (SMTP) to a Microsoft Exchange Server on the local
LAN. It has a few other ports being forwarded around the LAN as well, though
I don't think they're of importance. All of them seem to work flawlessly -
almost.

For the most part, everything works like a charm. SMTP mail comes through
fine to the Exchange Server and gets sent out fine - with one exception. Any
incoming mail from bellnexxia.net fails. That means nobody on Sympatico or
on Bell's Nexxia service can send me any e-mail. I've turned on the Exchange
Server logging to track the SMTP traffic. I can see the Bell server coming
in and negotiating with Exchange. After my Exchange server gives the "OK.
Send data followed by .... to end" (whatever it is, I can't recall), the
Bell server either issues a QUIT command or simply doesn't send any data and
my Exchange server times out after 5 mins of inactivity. I still get about
200-400 other e-mails a day coming from many different sources, but all Bell
Nexxia traffic bounces back to the sender in 3-5 days with a "network
problems" error.

Does anybody have any idea what's going on? Or does anybody know who I can
talk to about troubleshooting this problem? Rebel.com's support didn't help
at all and I can't find anybody at Bell to talk with to troubleshoot the
problem.

Peter Rofner
Tomato Pi
http://www.tomatopi.com