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CUCMBE DTMF tones not recognised on SIP trunk

Got a strange issue here...


CUCMBE 8.6(1) connected via a SIP trunk to a SP.

Inbound and outbound calling working fine for audio.

Inbound calls to one DN are directed into a CUC call handler. DTMF tones are not recognised by the CH (and are just ignored).

G.711 is being used as the codec.

I have tried the trunk with and without MTP (no change), and also configured early offer in my SIP profile (no change).

SIP trunk type is not secure.

Outbound DTMF works fine (calls from an IP handsets through to an external IVR over the SIP trunk is working ok when pressing keys).

Internal calls to my CH work fine and the DTMF tones are processed correctly.

I believe the SP is using RFC2833 for DTMF. I have tried configuring all DTMF options on my SIP trunk with no change.

Port monitor on CUC shows it not detecting any tones on an active call delivered through the SIP trunk.

However, if I call an IP phone over the SIP trunk, and press keys on the remote handset, I can hear them on my IP phone, although they do sound a little bit "clipped".

The really strange thing - with the same config on a 6.1(5) CUCMBE server, it all works fine - using the same SIP trunk provider and the same parameters on CUCM.

Any pointers as to where I should look next gratefully received!

Thanks. Barry


CUCMBE DTMF tones not recognised on SIP trunk

Fixed this issue. Turns out it is bug



No RFC-2833 DTMF signaled when events 0-15 aren't explicitly signaled

This bug was introduced in version 8.6(1).

It is fixed in an ES which is available from TAC on request.

Hope this helps anybody else that has the same issue.


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