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Re: ntp problem in broadcastclients




On Wednesday 24 October 2018 11:07:05 rhkramer@xxxxxxxxx wrote:

> On Wednesday, October 24, 2018 10:27:04 AM john doe wrote:
> > On 10/24/2018 2:44 PM, Greg Wooledge wrote:
> > > On Wed, Oct 24, 2018 at 08:22:49AM -0400, Gene Heskett wrote:
> > >> I has this machine running ntp normally, and set to broadcast on
> > >> the $local/24 network.
> > >
> > > I've never used NTP in "broadcast" mode.
> > >
> > > If it were me, I would simply use the normal configuration in
> > > which each client system has the NTP server's hostname or IP
> > > address in the /etc/ntp.conf file.  If it turns out this
> > > "broadcast" thing is the problem, then I'm not the right person to
> > > help.
> > >
> > > But...
> > >
> > >> Any clues of what else to check/change?
> > >
> > > Well, the obvious starting point would be "ntpq -p" on each
> > > system. This is the new version of "ntptrace" which apparently has
> > > been deprecated in order to make everyone's life harder.
> > >
> > > In addition to that, check the logs.  If these are wheezy boxes
> > > (or older) then you want /var/log/daemon.log*.  If they're systemd
> > > boxes, then you want (as root) journalctl -u ntp.
> >
> > In addition to the above, I would look at any kind of restriction
> > (FW...) between the clients and the server.
>
> I think that covers what I was going to say, but in an attempt to show
> off my knowledge (or lack thereof) ;-)
>
> As I understand it, NTP tries to get an approximate correct time for
> each client machine by doing something like measuring the round trip
> time to the server and back, then dividing by two, and applying that
> as a correction to the broadcast time from the NTP server.
>
> That was my understanding "back in the day" and I assume something
> similar is still occurring.
>
> On the other hand, it is hard to imagine that computers on your LAN
> have a latency anywhere near 70 seconds in communication from your NTP
> "server" on the same LAN (the one broadcasting the time).

Standard pings are in the 1 millisecond range.


-- 
Cheers, Gene Heskett
--
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