If you are cross connecting two servers or using a private internal network to connect your servers you will want to have the network identified as private.
Making network connection for backend connection / private IPs show as private instead of public. Then you can change the firewall permissions on the private networks to allow access for applications like SQL server.
If you are using a backend connection to cross-connect two servers, you may want the network connection to show as a private connection and have different firewall rules than with your public connection. We have found that in Windows Server, when a default gateway isn’t entered for a backend connection, the network will display as “unidentified network” and windows will automatically define it as a public network for firewall profile purposes.
Solution
Windows Server 2008 R2 – One workaround is to change the default in Windows so that unidentified networks default to the private profile. Under Administrative Tools, Local Security, Policy, Security Settings, Network List Manager Policies, then on the right hand side you can change Unidentified Networks to Private.
Windows Server 2012 R2
Administrative Tools –> Local Security Policy –> Network List Manager Policies –> (in right window) Unidentified Networks (double click). Here you can change the location type to “Public” or “Private” and you can change the user permissions to allow them to change the type.