James, MediaProxy has support for asymmetric UAs. You would still have to setup port forwarding at the border router where your client is located so is anything but plug-and-play. For each client that can be identified from User-Agent or Server field you place this information in: /etc/ser/rtp-asymmetric-clients /etc/ser/sip-asymmetric-clients And your mediaproxy module will know where to send the packets to. As Jiri mentioned this is a pain so please advise your vendor to change to symmetric signalling (Siemens, Wave3software and IPdialog did). Adrian We are using the example cfg from the cookbook for nathelper. It explicitly says it is only useful for symmetric UAs. Is there any mod to that config that will allow asymmetric UAs to also work? The goal here is to Do The Right Thing no matter what the users throw at us. -JimC