Asterisk Multicast (SIP)

How can I setup asterisk to dialog with sip devices using the Multicast transmission protocol ?

Basically I have an asterisk box conected to a VSAT network.

On the other end I have a SIP box in a network receiving the signal from the other VSAT.

The return from the SIP box to asterisk is unicast.

Is it possible to make it work ?

Thanks a lot!
ps. should I post it here or maybe other section ?