Internal Network IP (LAN)

Dear People,

to test i like configure a Public Server with Internet Connection (Windows) and a Windows Server without connection to the Internet.

How i can configure the PCs with a internal LAN IP and make it possible for the other one to connect to it?

What i do to try it.
I make in Proxmox a new Network card (vmbr1) and configure and create for the Internet Server a new Network card... For the LAN Server i use the main Networkcard.
I change the Networkcard from this Servers to vmbr1 and try to ping the other host -> not work. On the Networkcard settings in Proxmox i do nothing all fields are empty.


What can i do to work?

Sorry for my bad english.

I am from germany.

Thanks
Joni