We are running Callmanager version 4.2.3sr1. We have 1 Publisher and 1 subscriber at 1 physical location with about 200 phones. We are adding a second location with about 120 phones. I wanted to add a second subscriber and place it at the new location. Unfortunately Cisco does not sell CCM 4.2.3 anymore. We do not want to interrupt the environment of location 1, so upgrading to 5.x, 6.x is not an option. I want to move the subscriber from location 1 to location 2. Currently they are in the same CallManager Group. If I want the phones at location 1 to register with the local Publisher CCM first, and the Subscriber CCM for failover, and at location 2 I want the phones to register with the local CCM (Subscriber) then failover to remote CCM (Publisher). Is this doable? The 2 locations are connected via MPLS WAN.