If you are running a virtual environment with a DC and DNS server you are likely to encounter a problem with the internet connection or the network connection between your machines. The issue is that your machines can either get an IP address from the DHCP server in your environment or from your router. In case it takes the internal address you don’t have internet access. If the machine takes the external address it may not see the other machines in your lab.
A possible workaround is to create two virtual adapters: The first one to connect the machines internally, the second one to grant them internet access.
Here’s what to do to get it achieved:
1. Create an internal and an external virtual switch in the Virtual Switch Manager in the right pane of your Hyper-V management console. Leave the settings default.
2. Right-click the virtual machines and select Settings. Click Add Hardware and select Network Adapter. Create a second network adapter for each machine in the lab that needs internet access. In case your host is running on Windows 10 1709 or later, you should use the default switch that is already preconfigured (mind that you find an adapter vEthernet (Default Switch) in the list of Network adapter of your device). To my experience, this prevents the virtual switch from degrading the speed of physical adapter (you may check speedtest.net before and after the configuration to be sure).
The configuration gives you the option use RDP connections from your host computer which are more comfortable than Hyper-V connection. To allow RDP on servers, open the Server Manager, select Local Server and set Remote Desktop to on.
On workstations, open Control Panel, select System, go to the Remote tab and select Allow remote connections to this computer. Alternatively, configure the settings by GPO.
Btw, Microsoft provides an excellent lab with DC, DHCP, DNS, SCCM, MDT and many other installation as download on https://technet.microsoft.com/en-us/windows/mt604890.aspx
Managing the Hyper-V Default Switch in Windows 10 version 1709 and higher with PowerShell: https://mikefrobbins.com/2018/11/08/managing-the-hyper-v-default-switch-in-windows-10-version-1709-and-higher-with-powershell/