[ntp:questions] Re: NTP clients not syncing up to servers?

Brad Knowles brad at stop.mail-abuse.org
Tue Oct 11 21:53:31 UTC 2005


At 4:25 PM -0400 2005-10-11, Ted Beatie wrote:

>>  Also make sure that each ntpd instance has at least 4
>>  reliable, consistent, and _working_ lower-stratum servers
>>  configured before you even start ntpd for the first time.
>
>  What if we can't guarantee that?  The docs certainly seem to say that
>  the more the better, but that only one is actually required.  Some of
>  our deployments have public internet access, in which case, we can
>  populate the ntp.conf file on the gateway machines with as many servers
>  as we'd like.  But a fair number of our deployments don't have outbound
>  internet access, and have only one internal NTP server, if even that.
>  And yet, we still want at a minimum, for all of our machines to be in sync.

	Use either just one, or at least four.  Do not use either two or 
three.  The explanation is in section 5.3.3 at 
<http://ntp.isc.org/bin/view/Support/SelectingOffsiteNTPServers>.

	If you really care about having them all in sync, you'll set up 
reference clocks at each site, and make sure those servers are 
preferred by all clients.  Even if the sites in question don't have 
Internet connectivity, they can at least get a reference from an 
external source like GPS, CDMA, DCF77/CHU/WWV/WWVB, etc....

-- 
Brad Knowles, <brad at stop.mail-abuse.org>

"Those who would give up essential Liberty, to purchase a little
temporary Safety, deserve neither Liberty nor Safety."

     -- Benjamin Franklin (1706-1790), reply of the Pennsylvania
     Assembly to the Governor, November 11, 1755

   SAGE member since 1995.  See <http://www.sage.org/> for more info.



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