Windows NTP/SNTP Server Configuration


Windows NTP/SNTP Server Configuration


Need to sync time to phones, switches, routers, or other devices utilizing NTP or SNTP? Usually devices need a fixed IP address for a time server, rather than relying on DNS resolution. Here’s how to make the Windows Time Service work reliably.

There is a registry value located at HKLMSYSTEMCurrentControlSetServicesW32TimeConfigAnnounceFlags that controls how the Windows Time service (W32Time) will function.

The data type is a REG-DWORD, and information is available at

By default, the value is 10, which accounts for the following values:
0x02 Automatic time server
0x08 Automatic reliable time server

I’ve encountered servers that work intermittently, and best I can tell is the domain controller flips its determination on whether or not the server is reliable. It’s an easy fix, change the value from its default of 10, to 5 via regedit. The values for 5:
0x01 Always time server
0x04 Always reliable time server

If you do this, ensure you are syncing with a domain controller with a reliable time source or you configure a manual peer list on the local server. See this post for more information.

The other bit to double check is that the NtpServer component is still enabled. Look at:

The default value should be 1, but if it’s not present, or set to 0, change it to 1.

After making changes, restart the Windows Time service to make it take effect, and ensure the service is set for automatic startup.

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Daniel Holm

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