One of my customers is really concerned about redundancy (it's good). He want to establish an redundant solution for the IVR. The IVR is realized on two routers with the VXML scripts. On the CUCM I have established the route pattern, which points to the route list with these routers. I am using H.323 as a GW protocol. All inbound calls from two MGCP gateways are forwarded to the IVR.
The IVR script is pretty easy. The user has 5 seconds to dial an extension, after timeout he is automatically transferred to the operator. When user dials an extension he is transferred to this extension. During this procedure he hears the ringback. But when the call is transferred again -- the transferred user does not hear the ringback. The same may be observed, when the operator tries to transfer the call to some extension inside the office. In any case the transfer is successful with just one, but great disadvantage: the caller does not hear the ringback.