Windows Server 2003 behind router

Hi all,

I’m playing around with my server 2003 at home and trying to configure it as a domain controller with one nic card but I cannot connect to the internet after I promote the server as a domain controller and configure DNS server with forward look up zone. Below is my current home network configuration.

ISP –> Cable Modem –> Router –> Windows Server 2003.
Thanks for your help.
hhas4pnt