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DTMF mismatch issue

I have two clusters of CUCM like this:

IP Phone -------SCCP------CUCM cluster 1 ---------ICT trunk (gk controlled)-------Gatekeeper1------Gatekeeper2 -----ICT trunk (gk controled)------CUCM cluster 2------SIP trunk-----CUBE (to conferencing facility).

SIP trunk is configuured to use RFC 2833.

IP Phone is Cisco 7961 and supports RFC 2833 (confirmed).

SDI traces from CUCM in cluster 2 has the following DTMF mismatchi info:

16:37:59.697 |DET-MediaManager-(51187)::isMTPNeededForMismatchOrConfig, MTPNeededDueToDTMFCapMismatch(2833/OOB) mtpinsertionReason=1 dtmfMTPSide=2|9,100,21,44503.2^13.64.0.17^Port 52275

And due to the DTMF mismatch, an MTP is used.

My questions:

1 Why there is a DTMF mismatch? The IP phone is RFC 2833 supported, and the SIP trunk is RFC 2833 used, Why?

2 Is the ICT trunk anything to do with DTMF?

3 It is found  IP Phones (same model) registered to  CUCM cluster 2 does not have the DTMS mismatch issue. Why?

1 REPLY
VIP Super Bronze

DTMF mismatch issue

It certainly has something to do with the ICT. Your gatekeeper is configured with h323 dial-peers which can only support out of bound dtmf method. Hence you have a sip phone configured for rfc-2833 (inband dtmf) and ICT on outbound..

I had this issue in the past and the way around it is to enable sip kpml on your CUBE.

dial-peer voice 5 voip

dtmf-relay rtp-nte digit-drop sip-kpml

I am not sure whats going on cluster 2. Perhaps rfc2833 is disabled on the phone in that cluster...

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