What is a RADIUS Server?
RADIUS (Remote Authentication Dial-In User Service) is used for centralizing network authentication of remote access users. When you connect to an ISP you must enter your user name and password. This information is passed to a RADIUS server, which checks that the information is correct, and then authorizes access to the ISP system. RADIUS includes three components: an authentication server, client protocols, and an accounting server. The RADIUS authentication server is installed on a central computer on the network. The client protocols run on remote access devices such as remote access routers and firewalls. These RADIUS clients send UDP authentication requests, typically over port 1812, with MD5 encrypted passwords to the RADIUS authentication server and act on responses sent back by the server. RADIUS accounting captures statistics about sessions that are established to the network, and typically operates over UDP port 1813.
