Remote Access Dial-In User Services (RADIUS) is a distributed client/server system that assists in securing networks against unauthorized access, allowing a number of communication servers and clients to authenticate users' identity through a central database. The database within the RADIUS server stores information about clients, users, passwords, and access privileges including the use of shared secret.
RADIUS is a fully open and standard protocol, defined by two Requests for Comments (RFC) (Authentication: RFC2865, Accounting: RFC2866). You use RADIUS authentication to get secure access to the system (console/Telnet/SSH/EDM), and RADIUS accounting to track the management sessions (CLI only).
If you configure RADIUS using a fully qualified domain name (FQDN), the switch resolves the name to an IP address. You must configure a DNS server in the network to resolve the FQDN to an IP address.