[ntp:questions] client configuration: it's sufficient 3 servers ?

David Lord snews at lordynet.org
Fri May 24 09:56:49 UTC 2013

Riccardo Castellani wrote:
> If I have 3 internal NTP servers, what do you think if my clients have all 
> these 3 servers in their configuration ?
> According to '5.3.2. Why should I have 
> more than one clock?' in 'http://www.ntp.org/ntpfaq/NTP-s-algo-real.htm#Q-NTP-ALGO
> I read 2 servers, it's worst case, but also 3...

My four pool servers each have 5 x internet sources
(= 20 different internet sources) and 2 x local peers,
there are also local sources with MSF and GPS.

There is an explanation of the selection algorithm in
the ntpd documentation as to why having only 2 and 3
sources can give problems. That sets 4 as minimum and
5 for safety.

I've had internet outages where half the sources have
become unreachable.


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