I am working on a problem where about 70% of incoming calls from telasip.com are being disconnected immediately after I answer.
I have an asterisk server with a idefisk softphone and a SIP trunk to telasip for incoming calls. The asterisk server is on a private address behind a cisco PIX doing PAT on the outside interface. I am using dynamic dns. I have set my rtp.conf file to use ports 10001 through 10015. My firewall has a static translation from the outside interface to the internal IP of the server for udp 10001 - 10015 and udp 5060.
Sometimes it works fine but again, about 70% of the time the call is disconnected immediately after I answer it.