ntpd flipping between PLL and FLL mode

Michael Proto mike at jellydonut.org
Tue Dec 19 09:51:44 PST 2006

Jeremy Chadwick wrote:
> On Tue, Dec 19, 2006 at 10:56:22AM -0500, Michael Proto wrote:
>> An alternate workaround I've discovered is to use a maxpoll of 9 in
>> /etc/ntp.conf:
>> server rolex.peachnet.edu maxpoll 9
>> Since implementing this I haven't seen any of the FLL/PLL flips in my logs.
> How would decreasing the polling time fix this?  I do not understand
> the semantics/behaviour of NTP very well.
> Taken from the manpage:
>   maxpoll maxpoll
>           These options specify the minimum and maximum poll intervals for
>           NTP messages, in seconds to the power of two.  The maximum poll
>           interval defaults to 10 (1,024 s), but can be increased by the
>           maxpoll option to an upper limit of 17 (36.4 h).  The minimum
>           poll interval defaults to 6 (64 s), but can be decreased by the
>           minpoll option to a lower limit of 4 (16 s).

I made the change some time ago after combing newsgroups for this issue,
so my memory is a little hazy, but I seem to remember something about
the FLL/PLL switch being right at about 1024s. Check the Tuning section



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