When you configure a trunk or third-party phone to use the SIP protocol and Media Termination Point Required is enabled, Cisco Unified CallManager Administration only allows you to choose a G.711 codec in the MTP Preferred Originating Codec field. When you assign the SIP trunk or third-party SIP phone with the MTP required option enabled to the device pool for that region, you must verify that the region relationship between the SIP device and the MTP device is configured to use a codec with equal or greater bandwidth (G.711 or Wideband codec). MTP is not supported on SIP trunk while using codec g729.
SIP Trunk using G711 works with and without MTP
SIP Trunk using G729 works without MTP
SIP Trunk using G729 does not work with MTP enabled, even with transcoders.
I'm not able to access my old voice mail messages all of a sudden. The recording says something like 'the message is currently not available'. This has never happened before in all the years I have been using this system. I have t...