3.4.2.2 Realms

GNU Radius determines which server a request must be forwarded to by the request's authentication realm. There are three kinds of realms:

1. A named realm is the part of a user name following the at sign (`@'). For example, if the user name is `jsmith@this.net', then `this.net' is the realm. The named realms can be cascaded; e.g., a request with user name `jsmith@this.net@remote.net' will first be forwarded to the RADIUS server of the realm `remote.net', which in turn will forward it to `this.net'.
2. A default realm defines the server to which the requests for realms not mentioned explicitly in the configuration are forwarded.
3. An empty realm defines the server to which the requests without explicitly named realms are forwarded. If the configuration does not define an empty realm, such requests are processed by the server itself.

GNU Radius keeps the information about the realms it serves in the `raddb/realms' configuration file (see section 5.8 List of Proxy Realms -- `raddb/realms').