[ntp:questions] Re: Server Sync Problem

Harlan Stenn stenn at ntp.isc.org
Thu Dec 15 02:07:15 UTC 2005

> 3) Problem 1

> If I tell these servers to sync directly to the GPS server as clients,
> they do suceed, but then they lose sync for a few minutes and then find it
> again etc etc. NTP reports in /var/log/messages that "No servers
> reachable", but I have sat there with tcpdump running watching the UDP
> request/responses ticking away with no problems whatsoever. No packets are
> lost at all.  But NTP just doesnt seem to like whats going on.  However,
> if I make the client "burst" to the server, it never seems to lose sync at
> all. Why I need to use burst on a LAN when I cant see any packet loss, I
> dont know but it seems to fix the problem.

What version of ntp are you running?  If you said this, I missed it (sorry).
I recommend you try a recent ntp-dev snapshot; as soon as we fix a couple
more bugs it will become ntp-4.2.1.

> 4) Problem 2

> Now, if I sync a server lets call it A, off the GPS server, then try to
> sync the other servers off A, none of them will sync at all even though
> NTP can see server A and ntpq reports a reach of 377, the offset is < 1ms
> and the jitter is < .01ms and tcpdump sees all the UDP request/response
> packets without any problems.  So communication with the server appears to
> be fine, but NTP just doesnt want to sync up at all.

What does 'ntpq -p' show on this server?  What does your ntp.conf file look
like on it?  What about the ntp.conf file on your client machines?


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