RADIUS is a distributed client/server system that secures networks against unauthorized access. In the Cisco implementation, RADIUS clients run on Cisco routers and send authentication requests to a central RADIUS server that contains all user authentication and network service access information.
RADIUS is a fully open protocol, distributed in source code format, that can be modified to work with any security system currently available on the market.
RADIUS has been implemented in various network environments that require high levels of security while maintaining network access for remote users.
RADIUS does not support protocols such as AppleTalk, NetBIOS, and X.25. Figure 2-1 depicts the RADIUS authentication ...