We added a new fax station through an ATA [HT 286]. The call control signaling does not have any problem , however I can see that there is no voice channel between fax and the other end point. I setup a trace to examine the difference between our ATA FAX and a computer running the 3 CX phone. I made the call from the same station, here is what i observed:- 1. Call from station to 3cx - phone is set up properly 2. The 3cx phone receives a SIP invite, and this sip invite has rinstance populated in the header. 3. The 3cx phone sends the media to media gateway on a NATed IP address of the media gateway When I made a call from the same station to the Fax ATA this is what i observed:- 1. call from station to ata is setup properly. 2. the fax ata receives a SIP invite , but this packet is different in that it does not have a rinstance in the SIP header everything else remains the same. 3. The ata sends all the media to internal IP of the media gateway instead of the NATED IP and the call eventually gets disconnected. I have set the ATA to padd through mode for now. Please advice.