We just added a Cisco 2851 with 5 PVDM2-48's to our network. I have both hardware MTP and XCODE configured and registered to CUCM 6.1. We have a SIP trunk configured in CUCM that is set to "Use MTP". I'm noticing that a 'show dspfarm dsp active' on the 2851 shows that XCODE sessions are active, but I have not seen any MTP sessions active. I can see from a 'show sccp connections" that the XCODE's are xcoding g729b <-> g711 streams.
My question is how MTP and XCODE functions operate. If a g729 stream needs to connect to the SIP trunk via g711, will only an XCODE be invoked and no MTP? If both endpoints are g711, will MTP be invoked and no XCODE?