When you configure Network Policy Server (NPS) as a Remote Authentication Dial-In User Service (RADIUS) proxy, you use NPS to forward connection requests to RADIUS servers that are capable of processing the connection requests because they can perform authentication and authorization in the domain where the user or computer account is located. For example, if you want to forward connection requests to one or more RADIUS servers in untrusted domains, you can configure NPS as a RADIUS proxy to forward the requests to the remote RADIUS servers in the untrusted domain.
To configure NPS as a RADIUS proxy, you must create a connection request policy that contains all of the information required for NPS to evaluate which messages to forward and where to send the messages.
When you configure a remote RADIUS server group in NPS and you configure a connection request policy with the group, you are designating the location where NPS is to forward connection requests.
Configuring RADIUS servers for a group
A remote RADIUS server group is a named group that contains one or more RADIUS servers. If you configure more than one server, you can specify load balancing settings to either determine the order in which the servers are used by the proxy or to distribute the flow of RADIUS messages across all servers in the group to prevent overloading one or more servers with too many connection requests.
Each server in the group has the following settings:
Name or address
Each group member must have a unique name within the group. The name can be an IP address or a name that can be resolved to its IP address.
Authentication and accounting
You can forward authentication requests, accounting requests, or both to each remote RADIUS server group member.
A priority setting is used to indicate which member of the group is the primary server (the priority is set to 1). For group members that have the same priority, a weight setting is used to calculate how often RADIUS messages are sent to each server. You can use additional settings to configure the way in which the NPS server detects when a group member first becomes unavailable and when it becomes available after it has been determined to be unavailable.
After a remote RADIUS server group is configured, it can be specified in the authentication and accounting settings of a connection request policy. Because of this, you can configure a remote RADIUS server group first. Next, you can configure the connection request policy to use the newly configured remote RADIUS server group. Alternatively, you can use the New Connection Request Policy Wizard to create a new remote RADIUS server group while you are creating the connection request policy.
Remote RADIUS server groups are unrelated to and separate from Windows groups and Network Access Protection (NAP) remediation server groups.