Recommended Number of NTP Servers

Hal Murray hmurray at
Mon Nov 4 10:32:10 UTC 2019

Richard Laager said:
> The default for maxclock is 10. This includes the "pool" entries, of
> which the stock Debian configuration has four:
> pool iburst
> pool iburst
> pool iburst
> pool iburst

> As a result, the default is to use 6 pool servers. 

The pool entries shouldn't be counted as servers.  I don't know if refclocks 
are counted.

There is some hysteresis in there.  When starting up, I'd expect that setup to 
overshoot.  pool DNS lookups return 4 hosts.  pool 2 returns 4 each for IPv4 
and IPv6.  So after pool 0 it has 4, after pool 1 it has 8, and after pool 2 
is has 16.  Pool 3 may get 4 more if the ones from earlier work aren't "up" 
yet.  They get probed at 1 second intervals so there is a race between DNS 
lookup and NTP processing.

I don't know if it throws extras away or waits for them to die off.

These are my opinions.  I hate spam.

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