If you want to set up a test network where you want to run DHCP and/or a
local DNS server your best bet is to run all vms in Local Only on their own
IP subnet.

   Forget about Internet access or access to the host, just put your server
in Local Only, give it an IP address in its own IP subnet and proceed as you
would to set up a local network on its own switch. You can run DHCP and DNS,
even promote it to a DC without affecting the rest of your network.

   If you later want to connect this network to the physical network and/or
the Internet you can use a vm (not the DC) as a NAT router with one NIC in
Local Only and one linked to the physical LAN.