One-way VoIP audio

Define the missing direction

Write down who cannot hear whom. If the customer cannot hear the office, follow audio sent by the office toward the customer. Avoid the ambiguous statement that the customer has no audio.

One-way audio: find the missing hop

Most useful first checks

Compare an internal call, an external call and a call from another endpoint. A working internal call narrows the problem toward the path that changes at the carrier or remote-network boundary. Check mute and the selected headset before changing network settings.

Follow the media

Inspect the SDP address and port on each affected call leg, then compare actual RTP destinations. Determine whether packets leave the sender, reach the PBX and leave toward the receiver. Check NAT translation, firewall policy and whether direct media changes the expected path.

In Asterisk, inspect the loaded endpoint and topology-specific PJSIP NAT settings. In FreePBX, review the managed SIP/network settings through its supported interface. Do not paste standalone transport fragments over generated files.

Confirm the repair

Change only the setting supported by the evidence. Re-test both call directions, hold and transfer, because renegotiation can introduce a different media path. Keep the firewall enabled and remove temporary broad logging. A successful registration is not the acceptance criterion for this problem.