I have FXO trunks on a 2611XM router and have configured H323 between that gateway and a CUCM7.0 cluster which includes one publisher and one subscriber. I've configured and enabled media groups and lists, and both callmanagers service all 4 media functions. Calls function well, transfers work well, hold works well, etc...
Now as I want music on hold to be streamed to callers coming from the h323 gateway, I've enabled the "MTP required" option on the CUCM7's gateway definition for the 2611XM router. Following that, calls to/from the 2611XM can no longer be put on hold - pushing the softkey does nothing and the call remains connected.
This is a fairly vanilla setup. The media group has been assigned to the MRGL that is assigned to the device pool of the CUCM7 phone, along with the default device group.
Any hint is very welcome!!!