Fix one-way or no audio
Calls connect but someone can't hear. Usually a router or firewall problem.
When calls connect but audio is missing, call setup (SIP) works but the audio stream (RTP) is being blocked.
Steps
- Turn off SIP ALG on your router.It's on by default on many routers and is the most common cause.
Illustration. Your screen may look slightly different. - Make sure your firewall allows UDP on your provider's audio port range, often
10000–20000. - On the phone, set NAT to STUN if your provider gives you a STUN server, or turn on keep-alives.
- If you run your own PBX, check its external IP and local network settings.
- Test from another network, such as a mobile hotspot.If it works there, the problem is your office router or firewall.
Tip: Calls drop after exactly 30 seconds? That's a classic sign of SIP ALG or a firewall timeout.