DTMF Issue on 3cx V18

[nicoonline]

Hello,

Since long time the DTMF is not working according to RFC
https://www.rfc-editor.org/rfc/rfc2833

I see a telephone-event but no fmtp on the INVITE

SIP body received on the INVITE

v=0.
o=3cxPS 8561154620129280 4277939512279041 IN IP4 217.112.180.4.
s=3cxPS Audio call.
c=IN IP4 217.112.180.4.
t=0 0.
m=audio 7002 RTP/AVP 0 8 18 101.
a=rtpmap:0 PCMU/8000.
a=rtpmap:8 PCMA/8000.
a=rtpmap:18 G729/8000.
a=fmtp:18 annexb=no.
a=rtpmap:101 telephone-event/8000.
a=sendrecv.

when call is established we sent back the 200

v=0.
o=- 3903087341 3903087341 IN IP6 oit.olo01f.ipxsfwpstr11.ipcx.be.
s=-.
c=IN IP4 188.66.8.59.
t=0 0.
m=audio 26604 RTP/AVP 8 101.
a=rtpmap:8 PCMA/8000.
a=rtpmap:101 telephone-event/8000.
a=fmtp:101 0-15.
a=maxptime:30.
a=silenceSuppff - - - -.
a=rtcp:26605.
a=ptime:20.


Dtmf is not working.

 

[nicoonline]

I did some new tests and i can confirm that DTMF isn't working with the PC webclient.
on a deskphone it's working.

 

[SweetAction]

By any chance is this on a conference call? This is by design: https://www.3cx.com/community/threads/dtmf-tones-in-a-conference.67034/post-289026

https://www.3cx.com/community/threads/3cx-pbx-not-able-to-sending-dtmf-outbound.119292/

 

[nicoonline]

No, it's a simple call with PC Application.
I have tested with mobile and it's working.

 

[SweetAction]

So you are saying the DTMF using the 3CX Desktop App does not work, but does work with the 3CX Mobile Apps and IP Phones?

 

[nicoonline]

So you are saying the DTMF using the 3CX Desktop App does not work, but does work with the 3CX Mobile Apps and IP Phones?

That’s correct

 

[Alejandro_3CX]

That’s correct

So, are these external calls? If so what VoIP provider are you using?

What about internal calls dialing to an IVR?

 

[SweetAction]

That’s correct

Then I'm at a loss. If you are making a simple call, using the 3CX Desktop App, to a number and DTMF doesn't work and you are making the same call to the same number using the 3CX Mobile App and DTMF does work, you will likely need someone to assist who can work on the systems directly.

Can this be replicated on demand? Does it affect all extensions?

 

[nicoonline]

Hello,

I don't understand myself. I did some new tests and now it's working again
what is not clear for me is why the 3CX didn't send the fmtp: 0-15 in the SIP body.