Hello,
What you're looking into is EAP-TLS authentication. I think I know the pieces that need to be in place, but I have never deployed this type of network, just worked within it to troubleshoot issues.
Windows Server 2012 needs to be a CA, but also much have a PKI infrastructure deployed with group policy that tells domain clients to request personal certificates.
When the domain machine is deployed it will contact the Server CA and request a personal certificate signed by that Certificate Authority.
Group Policy must also then configure the machine for 802.1x with Microsoft Smart Card/Certificate.
You may also want to configure RADIUS certificate validation settings through group policy as well.
Also, GP should push the root CA certificate to the client.
The way this authentication should work is when the machine is plugged into an 802.1x capable port it will negotiate identify and authentication method information. After which NPS should send it's RADIUS certificate down to the client for validation. The client must have the root CA that signed the RADIUS certificate in order to validate the certificate. Once this is completed the domain computer will send it's personal certificate to the NPS server, where the NPS server will attempt to validate the client certificate based on if the CA certificate that signed the client certificate is in the trusted root store of the NPS server.
I can provide NAC configurations required to get this to work if NAC is the terminating RADIUS server, but haven't actually set this up on Microsoft Server.
Thanks
-Ryan