[ntp:questions] NTP 4.2.8p10 released

Martin Burnicki martin.burnicki at meinberg.de
Tue May 9 09:51:11 UTC 2017


ashu6486 at gmail.com wrote:
> Hi david,
> How can we add redundant server into  NTP 4.2.8p10 ? If we try to
> edit the configuration file it's not switching to the redundant
> server?

The NTP reference implementation (ntpd) does not use redundancy in the
way you might expect. I.e., you can't configure a "master" and a "slave"
time source and expect the client to use only the master and switch to
the slave when the master becomes unavailable.

Instead, you can configure several time sources, and ntpd periodically
checks them all, uses some voting process to see which send the same,
best, and most accurate time, and selects the "best" time source as
so-called "system peer".

The local system time adjustment is derived from the weighted time
offset from the system peer plus some other time sources which provide
similar accuracy.

If the selected system peer becomes unavailable then the client ntpd
discards it and selects a new one from the remaining time sources.

Please note that configuring exactly 2 time sources is the worst you can
do: if both time sources provide a slightly different time then the
client ntpd is unable to determine which one provides the "right" time.

Further reading:
http://support.ntp.org/bin/view/Support/SelectingOffsiteNTPServers#Section_5.3.3.
http://doc.ntp.org/current-stable/prefer.html
http://doc.ntp.org/current-stable/cluster.html


Regards,

Martin
-- 
Martin Burnicki

Meinberg Funkuhren
Bad Pyrmont
Germany



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