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Tech Tip: CUCM unable to synch time with Windows 2000 NTP server

Hi All,

There is a bug for this condition, sometimes when you use a Windows based NTP the time is not accurate.

CSCsd54013
NTP unable to sync time with Windows time server

<B>Symptom:</B>

Entering a Windows-based Time Service as an external Network Time Protocol (NTP) server results in NTP failure
on publisher.

<B>Conditions:</B>

Customer has Windows Time Service using Nt5DS or Simple Network Time Protocol (SNTP) set up on a Windows machine
and enters this machine's DNS name or IP address into the external NTP server list.  Post-install will fail
indicating that the external NTP server is unreachable.

Note that NTP and SNTP are different protocols and cannot be mixed.

<B>Workaround:</B>

The windows machine must be configured to use and serve NTP-based time synchronization.

<B>Further Problem Description:</B>

In Cisco Unified CallManager it is possible to have the cluster's time syncrhronized with a very accurate time
source or to use the primary node's system clock.  Relying on a system clock is subject to drift and can be especially
problematic if the system battery had died and a reboot occurs as the system clock could be way off.  If the
cluster is to synchronize with an external time source, it is necessary to configure the publisher to access a
server running Network Time Protocol (NTP).  Note that the external time source MUST NOT be Simple Network Time
Protocol (SNTP) as is commonly used in Microsoft Windows environments.

A Windows machine can be configured to to use NTP by setting a registry setting.

Note: To modify entries in the Windows 2000 registry, you must be a member of the Administrators group on the local
computer, or you must have been delegated the appropriate authority. If the computer is joined to a domain, members
of the Domain Administrators group might be able to modify the registry. As a security best practice, consider using
Run as when modifying the registry.

To open Registry Editor, click Start, click Run, and then type regedit.

Open the registry key: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\Parameters.

Right-click Type, select Modify and enter NTP.

Right-click NtpServer, select Modify and enter the Domain Name System (DNS) name or the IP address of an external
NTP server.

Open the registry key: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\TimeProviders\NtpClient.

Right-click Enabled and enter 1.
Open the registry key: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\TimeProviders\NtpServer.

Right-click Enabled and enter 1.

Public stratum 2 (do not use stratum 1) NTP time servers and NTP pool servers are available at  http://ntp.isc.org/bin/view/Servers/StratumTwoTimeServers and http://ntp.isc.org/bin/view/Servers/NTPPoolServers, respectively.  Be sure to read the rules of engagement at http://ntp.isc.org/bin/view/Servers/RulesOfEngagement.


HTH,

Tere Stevens
-----
Unified Communications PDI Team
www.cisco.com/go/pdihelpdesk

Version history
Revision #:
1 of 1
Last update:
‎08-10-2010 02:19 PM
Updated by:
 
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