From: Jonathan V Hays (jhays@jtan.com)
Date: Fri Jun 27 2003 - 18:36:33 GMT-3
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On
> Behalf Of Brian McGahan
> Sent: Friday, June 27, 2003 5:08 PM
> To: 'ccie2be'; 'Group Study'; 'Brian McGahan'
> Subject: RE: NTP hedaches
>
[snip]
> The key phrase here is "This may result in either a
> step-change or a gradual phase adjustment of the local clock to reduce
> the offset to zero." What this means is that depending on how far off
> your local clock is, you're either going to completely replace your
> clock with what the peer is advertising (step change) or move
> the clock
> closer and closer to the correct time (gradual phase adjustment).
>
> The reason that synchronization is happening immediately after
> you reload is because the 2500's don't have a hardware clock. This
> means that when they reload, the clock is reset to the
> default (00:00:00
> UTC Mon Mar 1 1993). Since both devices now have clocks that are
> relatively close to each other, the gradual phase adjustment and
> synchronization process will happen very quickly.
>
> On the other hand, if your local clock is very different than
> the clock source, it may take a long time for this gradual
> adjustment to
> happen, hence a long time until synchronization.
>
> To solve this problem, make sure that you configure the correct
> time (in UTC) on all devices *BEFORE* starting your NTP config. This
> will ensure that the change in offset during synchronization
> is minimal,
> hence a short time to synchronize.
>
>
> HTH
>
> Brian McGahan, CCIE #8593
Brian,
Excellent explanation!! The little light bulb is blinking furiously over
my head right now, and there is illumination inside my shriveled brain.
;-)
I have certainly noticed the "gradual" adjustment, or rather its end
effect. My method was to configure NTP on the routers, and then set the
correct time on the master to test. I would then check ntp clients
periodically while configuring other stuff, wondering why it was taking
so long to synchronize. But admittedly I never took the trouble to
investigate why.
Thanks!!
Jonathan
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