Depending on your Windows version, there are some registry settings you need to set:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\TimeProviders\NTPServer\Enabled
Changing the ‘Enabled’ flag to the value 1 enables the NTP Server.
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\Parameters\Type
Change the server type to NTP by specifying ‘NTP’ in the ‘Type’ registry entry.
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\Config\AnnounceFlags
Set the ‘Announce Flags’ registry entry to 5, to indicate a reliable time source.
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\Config\LocalClockDispersion
Set 'LocalClockDispersion' to 0
The last one is most important one.
After changing registry, you need to restart "Windows Time" service.
Then you may go to CUCM > OS Administration > Settings > NTP Server to configure the time source(windows DC) address.
Michael
http://htluo.blogspot.com
