Cistron Radius is a popular server, distributed under GPL. Cistron Radius can be found at:
When you configure the Cistron server for use with Extreme switches, you must pay close attention to the users file setup. The Cistron Radius dictionary associates the word Administrative-User with Service-Type value 6, and expects the Service-Type entry to appear alone on one line with a leading tab character.
The following is a user file example for read-write access:
adminuser Auth-Type = System Service-Type = Administrative-User, Filter-Id = “unlim”