[ntp:questions] Re: synchronization

Steve Kostecke kostecke at ntp.isc.org
Fri Mar 10 04:49:37 UTC 2006

On 2006-03-09, Richard B. Gilbert <rgilbert88 at comcast.net> wrote:
> Ron Croonenberg wrote:

>> Server ntp.conf:
>> ********************************************************
>> restrict default nomodify notrust
>> restrict
>> restrict xxx.yyy.zzz.0 mask nomodify notrap
>> noquery
> noquery, on a line by itself is invalid!!!

ntpd ignores invalid configuration directives.

> If it were valid, you would be shooting yourself in the foot because
> "noquery" means "do not respond to querys" which means your server
> couldn't serve time anyway!!!

'noquery' tells ntpd to ignore ntpq and ntpdc queries. Time service is
not affected. See http://www.eecis.udel.edu/~mills/ntp/html/accopt.html

> This is a pretty dismal looking ntpq banner!!


> How are you starting ntpd?  What options are you using?

The frequent time steps show in the log extract included in Ron's
original article suggest that his clock drift rate exceeds ntpd's
correction limits. This is the problem that must be solved first.

> Next, the three servers you are using appear poorly chosen.

This may be true, but it is hardly germane to the problem.

> You should be using four servers.

This is true, but it is hardly germane to the problem.

> Add the "iburst" keyword to each server statement.

This is true, but it is hardly germane to the problem.

>> server OS: Linux 2.4.21-4.ELsmp

ntpd instability on SMP 2.1.x kernels is mentioned at

I don't know if SMP 2.4.x kernels have similar problems.

>> restrict default ignore
>> restrict xxx.yyy.zzz.8 mask nomodify notrap noquery
>> restrict
>> server xxx.yyy.zzz.8
> I'd suggest removing or commenting out ALL the restrict statements until 
> you get everything else working.  Then you can uncomment or replace them 
> and see if they break anything.

His restrict statements are not blocking time service.

Steve Kostecke <kostecke at ntp.isc.org>
NTP Public Services Project - http://ntp.isc.org/

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