In Cisco CallManager 3.1 versions, upon transfer, the codecs for the Music On Hold (MOH) region and those supported by the server need to match. If they do not, the call is dropped. Calls to IP phones through a gateway fail when a transfer to another phone is attempted. This issue also applies to putting calls on hold and establishing conferences. Refer to Cisco bug ID CSCdv05335 for the latest details on causes, workarounds, and fixes. For more information on configuring MOH, refer to Music On Hold.
Go to Service > Service Parameters > Cisco IP Voice Media Streaming App. The DefaultMoHCodec parameter determines which codec is used when streaming MOH. To implement a workaround, select all that are required for your network. Update, stop and restart the IPVMSApps service.
To change the codecs used in the MOH server, perform these steps:
In the Cisco CallManager, select Services > Service Parameters.
Select Server > Cisco IP Voice Media Streaming App.
Select Supported MOH Codecs*, hold the Crtl key and click on all the codecs listed.
Click Update at the top of the page.
Select Application > Cisco Call Manager Servicability > Tools > Control Center > (choose server).
Stop, then start the Cisco IP Voice Media Streaming App.
Note: This may interrupt some services.
Alternatively, upgrade to Cisco CallManager 3.2 or later.