Intranet, Internet, Apple, Microsoft, Computers, Quantum, Linux, Networks

If wireless is ok then any WiFi network will do. Otherwise you’ll need a little hub or a switch. The real challenge is going to be DNS, unless you don’t need it (and plan to address everything by IP address).

You might also consider just buying one single powerful machine and running multiple virtual machines on it. Then you could use a virtual network instead of a LAN or WiFi.