kindly find the below
Media Termination Point (MTP) bridges the media streams between two connections allowing Cisco Unified Communications Manager to relay calls that are routed through SIP or H.323 endpoints.
The following MTP resources are supported for Cisco Unified Communications Manager
Software MTP—Software-only implementation that does not use a DSP resource for endpoints using the same codec and the same packetization time.
Hardware MTP—Hardware-only implementation that uses a DSP resource for endpoints using the same G.711 codec but a different packetization time. The repacketization requires a DSP resource so it cannot be done by software only. Cisco Unified Communications Manager also uses the term software MTP when referring to a hardware MTP.
Transcoder as MTP—Implementation that uses a DSP resource for endpoints using the same G.711 codec (on both legs) or a mixture of different supported codecs. This functionality is used by Cisco Unified Communications Manager to view the transcoders as usable MTP resources (if they are available in the pool) and enables Cisco Unified Communications Manager to use MTP resources more effectively when a call is deemed to use a transcoder and an MTP resource at the same time.
SO when intercluster you do not use MTP , when you check the call manager asked the router for DSP resouces and there is no configuration for DSP resources on router and no MTP configuration on Call manager , o the call is fail.The best is uncheck as you do
please rate if this will help