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Cisco Bug: CSCtd19129 - DTMF's not regenerated due to ill-digits

Last Modified

Feb 22, 2014

Products (1)

  • Cisco MGX 8800 Series Switches

Known Affected Releases


Description (partial)


VXSM is running 5.5(10.200) release when DTMF's not detected. 


The issue is only with VoIP users. 
DTMF detection for the IVR is performed by the VXSM card in the MGX which is configured to support RFC2833 in band event packets in the G.711 RTP stream.  Out of band telephony event packets are not used.

Test suggested that VXSM will mute the DTMF tones within the normal RTP stream and replace them with telephony event packets when a valid detection occurs.  Occasionally during a string of digits the original G.711 audio encoded DTMF tones comes through indicating that the VXSM erroneously assumed the tone was voice.  Also the failure of the DTMF detection does occur near the beginning of some of the DTMF strings.
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