[SR-Users] Kamailio with asterisk on private lan

Hi all I’m trying to create a relatively simple setup with Kamailio dual homed on public/private ip and asterisk on private ip only. The idea is load balance / fail over asterisk boxes. Following the real-time tutorial I have clients registering with Kamailio, Kamailio registering on clients behalf with asterisk as well as invites going through. However what I’m seeing is that when an invite occurs asterisk offers media on its private ip, as it would. However this is making its way through Kamailio all the way to the client. After a bit of searching all I can find is people trying to get it working and failing, or putting asterisk on public IP. So questions - am I doing this completely the wrong way? Should Kamailio alter the media ip of asterisk on the way through or do I need to do that by hand? Surely someone somewhere has a write up on this already :-) Thanks Mark