To setup a separate network, just change the subnet. If you are using 192.168.0.1/24 then you can use 192.168.1.1/24. This will effectively separate the networks. Network nodes are essentially connected by the network address and the broadcast address which are the first and last ip addresses of each subnet.
Additional Note: You could create the netwrok segment as mentioned above then use VLAN to isolate the network from your other domain. If you wish to not allow traffic to route to the virtual domain.
vmware communities will give you a step in the right direction.