I have 3 7975 series phones attached to a 3750 running advipservicesk9 12.2(44)SE6 providing PoE. They register to UCM running 22.214.171.12400-16. The configuration of the phones on UCM is pretty straight forward nothing fancy. The problem I am experiencing is the phones will continually register and unregister with the call manager. I can maintain a constant ping to all 3 phones throughout this process. I see no errors on any of the physical interfaces or the Tunnel interface. The 3750 connects to a 2811 with an IPSEC over GRE tunnel back to our main location. The tunnel is up solid as I said I can maintain a constant ping to all 3 phones whether they are registered or not. I can also web into the phones while they are registered.