Small network using ubuntu server 20.04LTS [closed]

I am trying to setup a small server and I want to know how I can set the computers up to be on the same network. These system will not have internet access. I tried using regular ubuntu and I was able to ping both machines when I connected them to the same router. But with ubuntu server, they don't seem to be getting IPs. Do I have to separately install a DHCP server on one of the machines when using ubuntu server for all the systems to get an IP address? Does ubuntu desktop come with this pre-installed while ubuntu server does not?

Generally your router will have a DHCP server in it to provide addresses for your machines, and desktop Linux will generally have DHCP enabled so it can accept addresses from the router. Ubuntu server may not; my own experience is that it generally does enable DHCP by default, but that experience is several years old. If you have a spare router, connect both the server and the desktop to the LAN side of the router; if you don't need Internet, you can leave the WAN socket empty. Check the network settings of your Ubuntu server to ensure that the network card has DHCP enabled. And with that you should be good.