On Fri, Sep 02, 2011 at 09:50:05AM +0100, Miguel Gonçalves wrote: > I found out the problem and just for the record I'll explain... > > The offset is larger than the delay because NTPd is using 10.0.2.254 (more > on this switch later) as a time source and it shouldn't because it has two > local stratum 1 clocks that are closer (0.170 ms vs 0.583 ms) are show less > jitter. Anyway... to prove my point I removed 10.0.2.254 (the **internal** > switch) from the configuration and here's the result of ntpq -p as of now:
It would be interesting to see the root distances for the three servers. I think it's reasonable to expect the weights of the stratum 1 servers to be much higher than the weight of the third server, so the combined offset isn't affected much by the third server. But what I think it's happening here is the high default dispersion rate (15 ppm) increases the root distance so much that the weights are not that much different. Setting "tinker dispersion" to a more realistic value like 1 ppm (or even to 0.1 ppm in your case, see my comment below) should help. You can also use "tos minclock 2" to limit the number of combined sources. > $ ntpq -p 10.0.2.2 > remote refid st t when poll reach delay offset > jitter > ============================================================================== > +10.0.2.10 .GPS. 1 u 889 1024 377 0.179 -0.066 > 0.083 > *10.0.2.9 .GPS. 1 u 391 1024 377 0.166 -0.084 > 0.051 Those are very good numbers for such high polling interval. Is the crystal oscillator thermally stabilized? In any case I'd suggest to use a shorter maximum poll interval. The default maxpoll is way too high for jitters normally seen on LANs if you want best accuracy. -- Miroslav Lichvar _______________________________________________ questions mailing list [email protected] http://lists.ntp.org/listinfo/questions
