Outline — full article in progress
This page has the structure and introduction. The full article is being written by the network team. In the meantime, ask us directly.
One-way audio is the most common VoIP fault that doesn't produce an error code: the call connects, but one side can't hear the other. It's almost always NAT, firewall rules or the RTP port range. This article lists the nine causes we see most and how to fix each one. For calls that fail outright, see SIP error codes.