Go to /etc/raddb/sql/mysql/dialup.conf file and find "Simultaneous Use Checking Queries" and there uncomment needed lines. then add simultaneous-use attribute to user. It worked for me.
From: Student University <studentmf@gmail.com>
To: FreeRadius users mailing list <freeradius-users@lists.freeradius.org>
Sent: Mon, August 30, 2010 11:31:03 PM
Subject:
Simultaneous-Use
Dears ,
anyone has been successfully configured Simultaneous-Use:=1
if so please share this experience .
Best Regards