[ntp:questions] Windows server sync to LocalCLK

Steve Kostecke kostecke at ntp.isc.org
Wed Jun 13 13:04:29 UTC 2007

On 2007-06-13, John <reply at newsgroup.com> wrote:

> I tried to start an NTP server on a XP Home box. The time source of this 
> box is the local clock.

The Undisciplined Local Clock (LocalCLK) is not a real time source. It
is intended to allow an ntpd to serve time to others in a "time-island"
or in the event that connectivity to real sources of time is lost.

If you have external network connectivity you really ought to use some
(i.e. 4, or more) remote time servers. But that's your choice.

> Now I have a linux box that tries to sync with this xp box

You really ought to do it the other way around. But that's your choice.

> but it doesn't work for at least 5 minutes of the NTP service
> starting. It returns error about stratum being too high.

ntpd can not serve time to others until it is synced to a source of

> I've searched around and people are saying that it takes about 5-8
> minutes before the server trusts the local clock as the source. Nobody
> has said why or if there is a way to fix this.

We've covered this question before in the news-group.

ntpd has to poll a time source 4 times before it collects enough data to
make the time source a candidate for use.

The default minimum poll period is 64 seconds.

The first poll occurs immediately after ntpd starts up.

4 polls takes ntpd_start_up_time + ( 3 * minimum_poll_period ) or ~ 200
seconds (3 1/3 minutes)

If you set "minpoll" to 4 the minimum poll period becomes 16 seconds.
This reduces the intial "sync" time to a bit under one minute.

	server minpoll 2
	fudge stratum 10

Steve Kostecke <kostecke at ntp.org>
NTP Public Services Project - http://support.ntp.org/

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