Set up Windows Radius Server.

Set up Windows Radius Server.

http://www.wikidsystems.com/support/wikid-support-center/how-to/how-to-configure-ias-to-support-two-factor-authentication

I am looking at the link above.
In our environment we have 2 domain controllers. I wan to set up IAS as Radius server and set  up VPN appliance as Radius client.

I want user authentication to be validated by our domain controllers DC1 and DC2.
I wonder whether by ,just authorizing RADIUS server in AD will do the job, or I need somehow to individually add DC1 and DC2 to Radius server.

Any help will be very much appreciated.

Thanks