No ringback when calling from IAX2 to SIP


I have some IAX2 softphones.
When I call from these phones to a SIP or PJSIP number, and the called party sends a 180 Ringing back, I cannot hear a ringback tone. Even if I do use the r or R option in the Dial command. Putting Progress() before the Dial command does not help either. (Then the called party still responds with a 180 Ringing).

So in case the called party sends a 180 Ringing, Asterisk does not generate the ringback tone.

When I do the exact same, but instead of using a IAX2 softphone, another SIP phone is used, the ringback tone is heard, in case a 180 Ringing is received. So in the scenario a SIP phone is calling another SIP phone, all is working fine.

What can I do to let Asterisk play a ringback tone on the IAX2 softphones after the 180 Ringing is received?

I am using Asterisk version 16.2.1.


It is normally the responsibility of the phone to generate ringback tone, when using VoIP. IAX2 is very closely based on Asterisk’s internal backbone signalling, so 180 Ringing should produce AST_CONTROL_RINGING, which should cause an IAX2 RINGING messages and the phone should respond by generating ringback tone.

See RFC 5456 - IAX: Inter-Asterisk eXchange Version 2

I’d suggest getting a protocol trace. If RINGING is being sent, the phone is at fault. To get Asterisk to generate inband ringback, I think you would need to answer the A side.

Asterisk 16 is less than a month from end of life, although the IAX2 code probably hasn’t changed for ages. If you do need to use Asterisk 16, for your own safety, you should be using 16.30.1.

Thanks for your quick reply!

This pin-pointed me to the problem. After having a look at the IAX2 debug log, asterisk/iax2 indeed sends the RINGING signal, but the softphone (Zoiper) is not handling it.

Thanks mentioning the outdated Asterisk version. I’ll ask my client to update.

Best regards,

Zoiper supports SIP, is there any particular reason for using IAX2?

I have it installed on my smartphone, ringback is present for calls, doesn’t matter using wireless or phone provider connection.

Sorry, here is complete reply. From my side, iax used to avoid FW problems. Appart of this, I love it and set it up as first connection even between 2 asterisk. Concerning the OP problem, I have zoiper installed on my smartphone using IAX2, ringback is present, doesn’t matter wireless or phone provider connection.

The IAX2 users are working from home. I have no control over their home network/router. Also the system is already running for about 10 years, and back then, this was the best/safest solution.

Indeed, IAX2 to avoid FW problems. In the Netherlands it seems that mobile providers generate the ringtone with early media (sip 183), and for some reason, that ‘wired’ phone providers do not do that, but send a sip 180 ringing.
The IAX2 users do not call others via the zoiper GUI, but Asterisk is making the call for them via their channel using the Dial command. Maybe that does matter too for Zoiper, since their was already audio going over the IAX channel.

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