Asterisk into rancher

I want to deploy an Asterisk based containers cluster into Rancher, but how I can deal with networking?

Without rancher I can manage it to work only if docker networking it is set to HOST, because asterisk needs rtp udp 10.000 - 20.000 ports and in case of one host with three containers I will need 3. different ip addresses here.

Also, how to deal with service discovery? Can I make some variables about service discovery to be inside the container for container use?