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New Member

Negotiating DTMF transfer mechanism


I have a DID provider who sends DTMF tones using payload-type 96 as opposed to a more common 101:

m=audio 5960 RTP/AVP 18 0 4 8 96 100 102 103 104 105

Apparently, AS5300 with c5300-is-mz.123-19.bin IOS can not negotiate DTMF transfer mechanism:

m=audio 19034 RTP/AVP 18

When I tried to enter command "rtp payload-type nte 96" on the incoming dial-peer, I got a message "ERROR: value 96 in use!". Is there a way to make Cisco speak payload-type nte 96 to the originating provider?

New Member

Re: Negotiating DTMF transfer mechanism

The problem with DTMF transfer mechanism negotiation is even bigger than I initially considered it to be. Inband-voice becomes the negotiated DTMF relay mechanism in cases when SDP offer from the caller contains codecs 18 96 100 (18 stands for g729) and also 18 101. In these cases the SDP answer from Cisco contains only 18. Only when SDP offer contains 18 101 100, Cisco puts them in the answer too and rtp-nte becomes the negotiated DTMF relay. I would find it incredible if I were the first one to run into this sort of problem. Any suggestions how to make the gateway respect payload types 96 and 101 without 100?

New Member

Re: Negotiating DTMF transfer mechanism

Hi Andrew,

Did you find any solution to this problem? I am having exactly the same problem and would apprciate any help!



New Member

Re: Negotiating DTMF transfer mechanism

Yes, i have remapped payload type cisco-codec-fax-ind which was using value 96 to a different number (102). This configuration works for me:

voice class codec 101

codec preference 1 g729r8

codec preference 2 g729br8

codec preference 3 g723r63

codec preference 4 g723r53

codec preference 5 g711ulaw


dial-peer voice 123 voip

application calling_card

incoming called-number 123

rtp payload-type cisco-codec-fax-ind 102

rtp payload-type nte 96

voice-class codec 101

session protocol sipv2

session target sip-server

dtmf-relay rtp-nte

no vad

New Member

Re: Negotiating DTMF transfer mechanism

Works for me too! Thanks very much for the info.



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