DOKK / manpages / debian 11 / ppp / pppd-radius.8.en
PPPD-RADIUS(8) System Manager's Manual PPPD-RADIUS(8)

radius.so - RADIUS authentication plugin for pppd(8)

pppd [ options ] plugin radius.so

The RADIUS plugin for pppd permits pppd to perform PAP, CHAP, MS-CHAP and MS-CHAPv2 authentication against a RADIUS server instead of the usual /etc/ppp/pap-secrets and /etc/ppp/chap-secrets files.

The RADIUS plugin is built on a library called radiusclient which has its own configuration files (usually in /etc/radiusclient), consult those files for more information on configuring the RADIUS plugin

The RADIUS plugin introduces one additional pppd option:

The file filename is taken as the radiusclient configuration file. If this option is not used, then the plugin uses /etc/radiusclient/radiusclient.conf as the configuration file.
Adds an Attribute-Value pair to be passed on to the RADIUS server on each request.
Sets Radius NAS-Port attribute to number equal to interface name (Default)
Sets Radius NAS-Port attribute value via libradiusclient library

To use the plugin, simply supply the plugin radius.so option to pppd, and edit /etc/radiusclient/radiusclient.conf appropriately. If you use the RADIUS plugin, the normal pppd authentication schemes (login, checking the /etc/ppp/*-secrets files) are skipped. The RADIUS server should assign an IP address to the peer using the RADIUS Framed-IP-Address attribute.

pppd(8) pppd-radattr(8)

David F. Skoll <dfs@roaringpenguin.com>