virtual network

I have a network of 16 computer through a switch. I need to put 3 of these computers on a virtual network so the other 13 pc’s will not have access to them. I also need to provide static IP’s but enable DHCP for visitors. What should I do and what equipment do I need for this setup? Would a router work? (I need all pc’s to have access to the server)
Thank you for your input.