[ntp:questions] broadcast client

Richard B. Gilbert rgilbert88 at comcast.net
Fri Sep 26 00:24:48 UTC 2008

rochertov at gmail.com wrote:
> Hello,
>   I have a question regarding broadcast mode.  I have 6 machines
> synchronizing with the same ntp server.  That server uses uses a local
> ntp displined clock (we are looking into a GPS one).  The machines are
> connected via 1 Gbps switch.  The network is lightly loaded and I
> configured the clients as such
> server ntp minpoll 4 maxpoll 4 iburst
> Howerver, I notice that two clients have a relatively large offset
> from the ntp server (greater than 100 micro-seconds according to "ntpq
> -p").  I considered setting the server into broadcast mode and
> enabling broadcastclient on the clients to avoid 6 machines polling
> the same server every 16 seconds.  I have two questions regarding
> this.  What is the syntax for setting the frequency of broadcasts on
> the server?  Also, how can I check the approximate time offset between
> the clients and the server?  Should I then peer each client with the
> ntp server and rely on broadcast messages for time synchronization?

Remove the "minpoll 4 maxpoll 4" and let ntpd work as designed.  When 
you force the polling interval to 16 seconds that way, you deprive ntpd 
of the ability to accurately measure and correct small errors.

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