What is the difference w.r.t to Call Preservation for H.323 & MGCP Gateways ? Which Gateway will preserve an on-going call, MGCP or H.3232 if the WAN link fails ?
Call Survivability and Call Preservation
Call preservation (aka call survivability) is a feature that allows active calls using a gateway to be preserved during a CUCM outage. Each gateway and trunk configuration device discussed in this post has a device pool with a Call Manager group configuration. The Call Manager Group configuration will accommodate up to three call managers for triple call processing redundancy. If communication to the primary Call Manager is lost, the gateway will communicate with the secondary Call Manager. If the secondary Call Manager is lost, the gateway will communicate with the tertiary Call Manager.
Media Gateway Control Protocol has supported call survivability (call preservation) since it was introduced on the gateway routers, but H.323 gateways did not support this feature until Cisco IOS 12.4(9T).
From this good article
Configuring H.323 VoIP Call Preservation Enhancements for WAN Link Failures
Please support CSC Helps Haiti