Quote Originally Posted by VOIPoJustin View Post
We find the vast majority of issues related to one way (or no way) audio as well as other connectivity problems to be NAT related. As such, we strongly suggest applying port forwarding (UDP/TCP) as a solution.

Think of the port range 5060 - 5080 as the 'control range,' whereby the adapter communicates back and forth with VOIPo's data centers, providing instructions on how to handle the call.

Separated from this control functionality is the audio stream (RTP), which connects on a randomized port between the range of 35000 - 65000. One key point to consider is that incoming audio is often proxied from different locations throughout the country, depending on the incoming audio's origination and geography.

Because of this separation in call handling and call audio, it is not uncommon for an incoming audio stream to reach the adapter from a completely different (and previously unseen) IP address. Occasionally, some hardware firewalls and SPI filter algorithms (erroneously) detect this incoming data as illegitimate, and block or otherwise prevent/manipulate it from reaching the adapter in tact.
What if one has more than one adapter?