It does, but its up to the NAS to really support it:
This Attribute indicates a dialing string to be used for callback.
It MAY be used in Access-Accept packets. It MAY be used in an
Access-Request packet as a hint to the server that a Callback
service is desired, but the server is not required to honor the
Dale E. Reed Jr. Emerald and RadiusNT__________________________________________IEA Software, Inc. www.iea-software.com
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