[c-nsp] Problems downloading from ftp.cisco.com

[Geert Nijs]

Hello all,

A customer of us has a really strange problem. He can't download anything
from ftp.cisco.com
He is sitting behind a Checkpoint Firewall. The Firewall admin says that
everything is configured correctly (we can download from other FTP sites).
I don't even get to the user login prompt ! We only get half a header at
Cisco:

*C:\>ftp ftp.cisco.com*
Connected to ftp.cisco.com.
220-  <}======[+]> FTP.CISCO.COM <[+]======={>
220-


-> That's all folks...........

*C:\>ftp ftp.microsoft.com*
Connected to ftp.microsoft.akadns.net.
220 Microsoft FTP Service
*User (ftp.microsoft.akadns.net:(none)): anonymous*
etc...

any ideas ?
We have debugged the issue until this level:

On the DMZ interface of -the same- firewall, it works. MTU of Servers in DMZ
is 1500 (default)
On the Internal interface of -the same- firewall, it doesn't work. The MTU
of the client PCs is set to 1300 (smaller, non-default). There are no MTU
issue up until the
firewall as the network can support MTU 1500

regards,
Geert