Looking for information on how to configure Radius to be able to authenticate to external network devices.

Here is good example configuring Windows Server 2012 with ASA 500 that will help you understand it http://www.petenetlive.com/KB/Article/0000685.htm. Configuration for R2 is the same. Take a look at Understanding and Configuring Network Policy and Access Services in Server 2012 series http://www.windowsecurity.com/articles-tutorials/Windows_Server_2012_Security/understanding-configuring-network-policy-access-services-server-2012-part1.html Also it will help as well - Network Policy and Access Services Overview - https://technet.microsoft.com/library/hh831683

Hi GSSourse,

Do you mean that you want to add a remote RADIUS server to authenticate for the network access server? Radius clients are network access servers, such as wireless access points, 802.1X-capables switch, VPN servers, and dial-up servers. Client computers, such as wireless portable computers cant be RADIUS clients.

If my understanding is right that you would like to use a remote RADIUS server to authenticate for the network access server, you can refer to the following documents

RADIUS server for 802.1X wireless or wired connections:

https://technet.microsoft.com/en-us/library/cc731853(v=ws.10).aspx

  RADIUS server for dial-up or VPN connections

https://technet.microsoft.com/en-us/library/cc731108(v=ws.10).aspx

Some reference about NPS:

https://technet.microsoft.com/en-us/library/dd197558(v=ws.10).aspx

Besides, when you have configured the RADIUS server and the network access server correctly, they can communicate with each other, no matter they are in the same subnet or not.

Best Regards,