We have CCM 4.1(3) in Greece, it dials out via an H323 gateway which is enabled on a 2811 series router, IOS version - 12.3(11)T2.
Problem - Internal conferencing works fine, but international conferencing doesn't. Suppose someone outside the cluster calls from US to Greece, the call is setup & then if the user wants to join another caller, say from Britian on a con call it doesn't work. Can something be done about this, I mean enabling off-cluster conferencing?
dial-peer voice x voice
voice class codec 10
That way it will try G.711 first instead of G789r8 which is the default codec for a voip dial-peer.
When a PSTN Call Terminates on a gateway, a VoIP leg is established between the gateway and the IP phone and therefore a codec is negotiated.
The negotiaited codec depends on the region settings in Call Manager, in this scenario we need to use G.711. Ideally the Phone, Gateway and the Conference Bridge should be in the same Region(and that Region should be configured to use G.711 for calls within region).
If they are not you will configure your regions so that G.711 is used between these regions for the conference to work.
Hope this helps,