Do SharePoint Servers need external adapters in Hyper-V?

I have two servers on Hyper-V in a development environment.

One has AD and SQL. One has SharePoint 2013.

Each server has two network adapters, one internal only and one external. On the AD&SQL server, the external adapter is turned off. From the SP2013 VM, I can ping the AD&SQL server by its IP address and hostname. I can also successfully ping the SQL Alias.

The AD&SQL server has DNS A records for each of my SharePoint Web Apps and SQL Alias. The SP2013 server has HOST file entries for the AD&SQL box and SQL alias pointing to the IP address of the internal adapter on the AD&SQL server.

Once I boot the VM, if I look at the network connections, the Internal Network status is 'Unidentified Network'. Once I turn the External adapter on, the status changes to the domain (sp2013dev.com) and remains that way once I turn the External adapter back off. Is there something that I am doing wrong or can I do something to prevent having to turn my adapter on and off again?