I think this question has been asked with different variables, but in my specific situation we want to host two independent companies on the same physical network without any interconnection. A.com would be the main host and AD of the existing company. We want to split off a new company called B.com. A.com would have IP addresses of 172.16.xxx.xxx and B.com would have IP addresses of 192.1.xxx.xxx and the two domains would not see or communicate with each other. The 172.16.xxx.xxx has the default gateway and is DHCP. Would it be possible to have B.com on IP address 192.1.xxx.xxx also use DHCP and would it need to use the default gateway IP address on the other subnet or would it have its own?
I want to make this as painless for myself as possible. VLANs are the last route I would like to explore.