[ntp:questions] NTP Peer Keeps Swapping on Start-up

David Woolley david at ex.djwhome.demon.invalid
Mon Oct 4 22:35:39 UTC 2010


SteveW wrote:
> On Oct 4, 4:40 pm, David Woolley <da... at ex.djwhome.demon.invalid>
> wrote:
>> SteveW wrote:
>>
>>> Also, just to clarify regarding the reach value, the snippet I showed
>>> is right at start-up and it quickly goes to 377 for the remote ntp
>>> server and remains there.
>> ntpq assoc, followed by ntpq rv for the association number.
>>
>> Typically the problem is that the local clock has rather narrow error
>> bounds, and if the remote source disagrees, but also has narrow error
>> bounds, there is conflict as to which one has the true time.  If you
>> have a legitimate need for a local clock, you should make sure all your
>> local clocks can be outvoted by real clocks.
> 
> How do I make sure the local clocks can be outvoted by real clocks?

You ensure that more server lines reference servers traceable to true 
time, than reference servers dependent on a local clock.

> Also, here is the result from debug:
> 
> [16:53:13] ind assid status  conf reach auth condition  last_event cnt
> [16:53:13] ===========================================================
> [16:53:13]   1 58883  9424   yes   yes  none candidate   reachable  2
> [16:53:13]   2 58884  963a   yes   yes  none  sys.peer    sys_peer

Neither is being rejected, but I guess that the anti-clock hopping logic 
is in effect.  If this weren't the local clock, I would say the time was 
being disciplined by a combination of both sources.  I'm not sure what 
happens with the local clock.  rv 0 will tell you what offset value is 
being used to discipline the clock.  If only the local clock is being 
used, it will be zero.




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