From the command line type “list trace tac 1111/s” (1111 being the tac code), this provides a sip trunk trace.
To enable an mst on the trunk type “clear mst” followed by “change mst default” and enable the following settings.
Log Mst? y
Trace Analyzer? y
SIP Trunks? y
SIP Filter Data – Signaling Group: 111 (111 being the trunk signalling group).
Now type “enable mst” make your test calls and then type “disable mst”.
Now go to your web browser and logon to the CM server, goto Maintenance Web interface, goto Diagnostics and select System Logs, check Communication Manager’s interpreted Message Tracer (MTA) and you will be able to view the logs.