Does IAS support callback?
If you configure the Set by Caller callback option on the dial-in properties of the user account, IAS returns the Service-Type=Callback-Framed attribute. This behavior is not clearly specified in the RADIUS RFCs and some NASs might not support this option. See your NAS documentation for more information. If you configure the Always Callback to option on the dial-in properties of the user account and configure a phone number, IAS returns the Service-Type=Callback-Framed and Callback-Number=”configured number” attributes. IAS conforms to the recommendation of the RFC, but some NASs might not. See your NAS documentation for more information.