Enable RADIUS authentication

1. Install an IAS server. To ensure that RADIUS authentication and accounting services remain available, configure both a primary IAS server and one or more backup (secondary) IAS servers to provide redundancy and fault tolerance.
   
2. Register the IAS servers in the appropriate Active Directory domain.
   
3. Configure the primary IAS server with RADIUS clients corresponding to your answering routers.
   
4. Configure each answering router with the RADIUS servers of your primary and secondary RADIUS servers.
   
5. After you enable the Routing and Remote Access service, configure remote access policies that reflect your dial-up or VPN connection requirements on the primary IAS server. For more information, see "Configure the Routing and Remote Access Service and Demand-Dial Interfaces" and "Configure a Remote Access Policy" later in this chapter.
   
6. Configure logging methods for user authentication and accounting requests.
   
7. Copy the IAS configuration (including the remote access policies) from the primary IAS server to the secondary IAS server.