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Cisco Bug: CSCup59745 - SIP 69XX phones do not play audio after 488, ICMP port unreachable seen

Last Modified

Nov 27, 2020

Products (1)

  • Cisco SIP IP Phone Software

Known Affected Releases


Description (partial)

A 69XX (6901, 6911, 6921, 6941, 6961) does not play audio so silence is heard even though RTP packets arrive at the phone.

69XX running SIP firmware with call recording enabled using the BIB.  Place a call to the 69XX so that the region mapping between the calling phone and 69XX phone is g729.  Answer the call on the 69XX phone and recording will automatically start and setup as g729 using the BIB to the recorder.  Then from the calling phone that called the 69XX, place the call on hold.  If the region mapping between the 69XX phone region and the MOH server region is set to g711, CUCM will offer g711 to the phone for MOH.  The phone due to being codec locked to g729 due to recording will reply to the g711 SDP from CUCM for MOH with a 488 unacceptable media as expected.  Then CUCM will then offer MOH with g729 because both g711 and g729 are enabled under the IPVMS service parameters for MOH.  The phone sends a 200 OK with SDP (IP and port) for g729 and CUCM starts sending RTP packets to the IP/ port the phone put in the 200 OK.  The phone however does not open the RTP ports so we see the phone replies with an ICMP port unreachable for the RTP packets arriving at the phone for MOH.  The user experience is that they hear silence instead of music on hold in this case.
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