I have a problem with CUCM & SCCP IP Phones NTP synchronization. My problem is although I have defined a NTP Server in CUCM configuration, neither phones nor CUCM servers synchronize their clocks with the NTP server. The NTP server is a Windows 2003 Server SP1 and CUCM version is 22.214.171.1240-1.
It's important for me to solve this problem.
I believe that Windows uses SNTP rather than NTP and that this is not supported by Cisco devices including CUCM, routers, switches etc.
Try synching CUCM directly to an NTP source rather than to Windows.
For more details check out the link below: