Each user or computing device that connects to a Remote Desktop Session Host (RD Session Host) server must have a valid Remote Desktop Services client access license (RDS CAL) issued by a Remote Desktop license server.
After you have installed and configured the license server, you need to do the following on your RD Session Host server to ensure that the RD Session Host server can contact the license server to request RDS CALs for clients:
Specify the Remote Desktop Licensing Mode on an RD Session Host Server
Specify a License Server for an RD Session Host Server to Use
To be alerted to possible licensing configuration issues, use Licensing Diagnosis in the Remote Desktop Session Host Configuration tool. For information about Licensing Diagnosis, see the topic "Identify Possible Licensing Problems for the RD Session Host Server" in the Remote Desktop Session Host Configuration Help in Windows Server 2008 R2.