how to configure DC as NTP server

Does this help:

w32tm /config /manualpeerlist: NTP SERVER /syncfromflags:manual /reliable:yes /update


http://technet.microsoft.com/en-us/library/cc786897(WS.10).aspx

Windows domain controllers have build-in ntp server.
You can check it in linux:

ntpdate <dc_ip>

Select allOpen in new window

The root PDC DC will need to be configured to get it's time from an external time source.  You will need to stop and start the time service when you configure it

The root PDC need to be configured from Machine Clock , No need to be from External time source
It should act as NTP server also

How to know that 2003 DC is a NTP server or not

http://blogs.msdn.com/b/w32time/archive/2008/04/02/configuring-a-standalone-time-server.aspx

This command for windows 2008 ,   I am lookig for windows 2003  R2 DC,

1) how to DC is NTP server or not
2) how to configure DC as NTP server

The Call manger servers if domain members will get their time from the domain controllers via NTP using NT5DS.

To confirm on the Call manager server open a cmd prompt and enter the following:
reg query hklm\SYSTEM\CurrentControlSet\Services\W32Time\Parameters /v type

The PDCe is time and if configured to sync with an external source then some registry changes are required as noted in above posts.

Also see:
http://support.microsoft.com/kb/816042
and
http://technet.microsoft.com/en-us/library/cc786897%28WS.10%29.aspx

ensure port 123 udp is open if using a firewall.

Answer is correct