Isolate test lab from network, but still access internet?

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http://serverfault.com – I'm setting up a 2003 Server vm for testing purposes as a AD controller with DHCP. It's connected to a network with a DSL router already serving DHCP addresses to numerous other client machines. I've configured the server vm with 2 NICs. One is connected to the 'real' network of the DSL router. Server is and the router is The other is connected to the virtual host only network, with an address of This will be the address I want to configure for the test lab to do AD, DNS etc. How to I configure it, such that the physical machines on the network (HowTos)