[ntp:questions] Choice of local reference clock seems to affect synchronization on a leaf node

Nathan Kitchen nkitchen at aristanetworks.com
Wed Nov 9 03:53:56 UTC 2011

On Tue, Nov 8, 2011 at 7:27 PM, Dave Hart <hart at ntp.org> wrote:
> On Wed, Nov 9, 2011 at 03:12, Nathan Kitchen
> <nkitchen at aristanetworks.com> wrote:
> > On Tue, Nov 8, 2011 at 6:59 PM, Dave Hart <hart at ntp.org> wrote:
> >> I agree that I would not expect to see any difference in behavior
> >> between LAN source only (#1) and LAN source + orphan mode (#2).  I am
> >> not surprised to see difference in behavior with 4.2.6 between either
> >> of those and using a LAN source and the LOCAL driver (#3) as that
> >> version is prone to switch to the LOCAL driver more often than is
> >> helpful.  If you stick with that version of ntpd, I would advise
> >> avoiding the LOCAL driver, and I would also wonder if even orphan mode
> >> is helpful in this case.  Why not use config #1, what problem is LOCAL
> >> or orphan mode solving?
> >
> > It doesn't exactly solve a problem, but faster synchronization is nice
> > to have, and it does appear to have that effect.
> In the case of LAN source + orphan mode, what is the refid reported by
> ntpq immediately after the faster synchronization?  If it is
>, the sync is illusory, as it's really self-synced.

The log I have on hand at the moment only has the output of ntpstat at
the point of synchronization, but I think it's enough information to
tell that it's not a self-sync:

synchronised to NTP server ( at stratum 4
   time correct to within 98 ms
   polling server every 64 s

-- Nathan

> Referring to:
> http://doc.ntp.org/4.2.6p1/miscopt.html#tos
> I see 4.2.6p1 does not have "tos orphanwait" at all, so orphan mode
> will be entered immediately after the big clock step, but only
> temporarily until enough samples come in from the network source for
> it to be selectable.  FYI, current 4.2.7 extends orphanwait to also
> hold off selection of backup reference clocks such as LOCAL and ACTS
> modem to give other sources a chance and avoid transient clock
> hopping.
> > Thanks for the insight on the appropriate use of LOCAL and orphan mode.
> You're welcome.
> Cheers,
> Dave Hart

More information about the questions mailing list