I'm trying to get secure trunks set up between our cluster and SBC. The trunk is up and calls are working. However, when I try to place a call on hold from the cucm side the call breaks down. I've identified the cause of this. During the re-invite, CUCM tries to send regular RTP back instead of SRTP for the MOH. According to the docs, if the remote device supports SRTP then CUCM should send SRTP for MOH. However, this is not what is happening. I've verified that this works from a secure cucm phone to another secure cucm phone. But this does not work from a secure cucm phone across a secure trunk. Any suggestions? I've restarted the IP Media Streaming service and that had no affect. I'll share a snippet of the SDP below where CUCM sends RTP instead of SRTP -
v=0
o=CiscoSystemsCCM-SIP 166772 3 IN IP4 <X.X.X.X>
s=SIP Call
c=IN IP4 <X.X.X.X>
t=0 0
m=audio 4000 RTP/AVP 0
a=X-cisco-media:umoh
a=ptime:20
a=rtpmap:0 PCMU/8000
a=sendonly
