[ntp:questions] Ntp looses sync
david at ex.djwhome.demon.co.uk.invalid
Thu Apr 2 07:45:40 UTC 2009
Heiko Gerstung wrote:
> I know NTP appliances that allow you to configure the stratum level of
> the unit when it is in holdover/free running mode. There is a good
> chance that the Gude box allows for the same. Did you check that with
> their technical support?
Setting the local clock stratum to a lower number than one gets from
real network is considered bad practice, because it risks accidentally
serving time to something that doesn't realise it is getting time from
an unsynchronised source.
I'm actually of the opinion that providing a "local clock" pseudo source
should always be an opt in, but, unfortunately, it tends to set up as an
opt out when people package ntpd.
Also, it is very rare to have a real stratum 5 server, so I wonder if
this is also a case of inappropriate enabling of a local clock driver; I
think that stratum 5 is the default local clock driver stratum, which is
probably based on the assumption that there is some, reliable, non-NTP,
discipline for the machine's clock. The appliance is using a
recommended local clock stratum for a free running oscillator.
If the 5 is the result of a local clock driver, that should be removed
from the relevant configuration. Serious consideration should be given
to removing the local clock driver from the appliance configuration, as
its clients will coast at the last known frequency, so shouldn't diverge
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