[ntp:questions] peer command and clusters

Dave Hart hart at ntp.org
Sat Mar 26 15:46:53 UTC 2011


On Sat, Mar 26, 2011 at 10:36 AM, "Rob" <ineedtoread at RFCs.example.com> wrote:
> Florin Andrei <florin at andrei.myip.org> wrote:
>> ###########################################################
>> server 0.us.pool.ntp.org
>> server 1.us.pool.ntp.org
>> server 2.us.pool.ntp.org
>> server 3.us.pool.ntp.org
>>
>> restrict 0.us.pool.ntp.org mask 255.255.255.255 nomodify notrap noquery
>> restrict 1.us.pool.ntp.org mask 255.255.255.255 nomodify notrap noquery
>> restrict 2.us.pool.ntp.org mask 255.255.255.255 nomodify notrap noquery
>> restrict 3.us.pool.ntp.org mask 255.255.255.255 nomodify notrap noquery
>
> This does not work!
> The names like 0.us.pool.ntp.org return multiple IP adresses and
> the "server" and "restrict" lines will not match.

"Rob" is correct with respect to older ntpd.  See ChangeLog or other
public sources for the timeline, but newer ntpd behaves differently,
and will add a restriction for each of the IP addresses a name
resolves to, where older ntpd added only one.  I predict with such
ntpd the above works fine, but it's far from what I'd recommend.

As unruh explained, with recent-enough ntpd the low-maintenance way to
achieve the same result is to replace the four restrict lines with a
single "restrict source", which defines a prototype restriction
automatically applied to servers the client is using, particularly
handy with the 4.2.7 rework of the "pool" alternative to "server",
which can drop and add servers automatically as conditions change.

You probably want iburst on each of those server lines, to sync the
clock in under 15 seconds instead of a few minutes.



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