No audio on inbound route if the destination is sip trunk


I’m new to FreePBX and am having trouble setting up an inbound route to a Twilio programmable SIP. When I call the number from my mobile phone, the call connects but there’s no audio. I’ve enabled recording, but it’s always 44 bytes with no data.

I’ve also created an outbound route with the same destination, and when I call from a softphone to any number, the call connects to the Twilio SIP destination and I can hear the audio. The call is also being successfully recorded.

If I set the inbound route’s destination as an extension, the call works successfully.

I’ve been trying to figure this out for the past week with no luck. Any insights would be greatly appreciated.

Assuming that this is an on-site PBX behind a NAT:
In your router/ firewall, forward the RTP port range (default is UDP 10000-20000) to the LAN address of the PBX.

If you already have this or it doesn’t help, describe your network setup in detail.

Thank you for your reply.

I made the following port forwarding in the router.

Also, within the Asterisk SIP settings, for the Nat settings, I have added the External Address(the device public ip), and for Local Networks as / 24

Here are the active Codecs in my sip settings:
uLaw, aLaw, g719, g722

Here is how my hardware setup :
I connected a GSM dongle to my RaspberryPi in it I’m using RasPBX.

What could be the issue here?

I’m guessing that the incoming audio is still being blocked until some RTP is sent.

To test, route the DID to your extension. Turn on Follow Me with the destination number followed by # in the list. I would expect to see the same symptoms – call completes but no audio. Then, set Play Music On Hold to default and retest. Report whether caller hears the music and the callee.

I followed your instructions and called the DID from an external phone. The call came to the extension and then to the follow-me extension. When I answered the follow-me extension, I could hear the voice on both sides. However, for the initial two seconds, I could hear some cracking sounds. I experience similar sounds occasionally when setting the destination as Twilio SIP.

Considering the symptoms, what could be the issue here?

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