I've been having issues getting inbound calls to work with my SIP trunk provider...basically all I heard once the call connected was 'dead air'. After reading through the forums I found a post that said that the SIP provider may not be following the RFC and to put the following into my SIP configuration:
voice class sip-profiles 1
request ANY sdp-header Connection-Info remove
response ANY sdp-header Connection-Info remove
Now I can't get DTMF to work with inbound calls through the SIP line. The call answers and hits the auto-attendant, but I can't select any of the options.
I know the AA works fine, because I can test it internally.