[ntp:questions] NTP.log interpretation

Charles Swiger cswiger at mac.com
Mon Apr 21 17:24:45 UTC 2014


Hi, Greg--

On Apr 21, 2014, at 9:13 AM, GregL <greg.leibfried at gmail.com> wrote:
> What you are saying is that if we are currently using a DNS load balancer
> appliance to point 'ntp.host' to ntp1.host or ntp2.host (ntp1 unless it
> fails, then to ntp2)....    that is really isn't doing us any good, because
> that only dns lookup is only ever done when xntpd starts.   Once it gets
> the IP address on startup, it always uses the numerical IP address to send
> out it's UDP requests.   Is that correct?

That's largely correct, yes.  (Certainly for anything old enough to be called xntpd.  :-)

> Not even if the IP fails to respond to requests, will it try the DNS lookup again?

Modern versions of ntpd have a "pool" directive which can be used in place of "server";
when using pool, ntpd will re-query DNS and hope to get a different IP if the
current IP fails to respond:

  http://www.eecis.udel.edu/~mills/ntp/html/discover.html#pool

Regards,
-- 
-Chuck



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