Default gateway has a mind of its own

[bpinter]

Hi everyone. I'am not sure if this is a Watchguard issue or a Windows issue but maybe you TCP/IP gurus can give me an idea where to start looking.

I have a Watchguard X500 with a LAN and a DMZ network. The Watchguard has a public IP and there is a webserver on the DMZ and a MS SBS 2K3 server on the LAN. The servers are:

SBS:
IP: 192.168.1.1/24
Gateway: 192.168.1.100 (the LAN port of the Watchguard)

Web Server:
IP: 192.168.2.1/24
Gateway: 192.168.2.100 (the DMZ port of the Watchguard)

Now the issue is that when a remote desktop connection is used to connect from the LAN to the webserver from an XP machine on the LAN the following happens: The connection is made, the logon screen is presented, but after logging in successfully, the connection drops out. Checking the server from the console then shows that the default gateway setting on the Webserver's NIC has changed to 192.168.1.100 (the LAN default gateway.) What the...? Changing this back to 192.168.2.100 then restores the connection and it can be used without any problems. The connection is not used every day but next time same problem.

It's driving me nuts! Any ideas anyone?

 

[SimonDavies]

How often does this happen? What should happen is that each NIC keeps it's own information associated with that NIC.

Can you get this to happen every time?

 

[bpinter]

Yes, it happens every time. Having said that, if we connect and it happens. Once it's fixed it doesn't happen again from the same PC on the same day. Because we don't do this every day, it's hard to say when it 'resets' so to speak. Certainly given a couple of days between attempts (probably even one day) it happens every time.

 

[SimonDavies]

Have you seen anything in the event viewer? Have you double checked both of the NIC's settings?

 

[bpinter]

It turned out to be the SBS logon script. It apparently sets the default gateway to the SBS configured one every time it runs. Thanks for yor help.