FTP-Data connections?

[fernando_montenegro () hp com]

Hi everyone!

I've just come across a curious problem, and I wonder if you guys can help me...

When connecting to a remote FTP server (I've tried ftp.microsoft.com, 
ftp.redhat.com and ftp.cdrom.com, among others) from a command-line FTP client 
(running on Linux), the standard FTP control connection works fine, but the 
data connection (on 20/tcp) never gets established.

The weird thing is that the control connection reports "No route to host" after 
it fails to connect back to my client on a high port. No traffic ever reaches 
the local LAN or the connecting router.

Passive mode doesn't work either.

This is happening off one particular ISP, who assures me they have no filtering 
whatsover installed. When testing off a different ISP, things work out fine 
(data connection gets established and transfers work without a glitch).

Can anyone shed any light on what might be causing this? If there was no route 
back, the control connection wouldn't be established, would it?

I am wondering if the ISP didn't add a stateful packet filter somewhere up the 
route and forgot to mention it to us. Any other ideas?

ObFirewalls: When this finally works, the ISP link on our end will be protected 
with a Firewall. Before making by job harder by adding the firewall into the 
equation, I'm testing the simple stuff first...

Thanks!

Cheers,
Fernando
--
Fernando da Silveira Montenegro     Hewlett-Packard Brasil
HP Consulting - Internet Security   Al. Rio Negro, 750 - Alphaville
mailto:fernando_montenegro () hp com   Barueri, SP - Brazil 06454-000
voice: +55-11-7297-4351             #include <disclaimer.h>