[cisco-voip] RightFax SIP/T38 and DTMF

Wed Dec 5 10:24:07 EST 2012

RightFax sending fax across SIP Trunk to CallManager that had Device > Trunks to 2811 that have Early Offer

Faxes fail.  Seeing CallManager Software MTP being invoked.

"RigthFax doesn't support any type of DTMF, whereas the SIP Trunk supports
RFC2833, the CUCM understands this as a mismatch and allocates the MTP:
MTP_DHSCCMSUB4. Below the initial INVITE coming from Rightfax where you can
see inside the SDP there is no DTMF attribute"

Anyone aware of this and if RightFax has a fix to for RightFax to include DTMF attributes in their SIP SDPs so MTP doesn't get invoked?
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