[ntp:questions] NTP driving me nuts!

Danny Mayer mayer at ntp.isc.org
Thu Dec 28 15:49:42 UTC 2006


JCA wrote:
> On 12/27/06, Danny Mayer <mayer at ntp.isc.org> wrote:
>> JCA wrote:
>> >    I have three Linux boxes, A, B and C, running ntpd. C gets its
>> > synchronization from some external, stratum 2 server, whereas A and B
>> > get their synchronization from C, as a stratum 3 server.
>> >
>> >    This setup has been working fine for months. A couple of days ago I
>> > noticed that A and B did not seem to be in sync any more. I restarted
>> > ntpd in A and B, making sure that A and B were synchronized with C by
>> > hand before. They both started fine but, surely enough, they did not
>> > seem to be keeping up with C - the local clocks on A and B started to
>> > diverge as though ntpd were not running at all.
>> >
>> >    C is reachable from A and B without any problems. In turn, C stays
>> > synchronized with the external server all right - always within 0.05
>> > seconds. Nothing has changed in A, B and C within the last few months.
>> > I just can't understand why, all of a sudden, A and B are no
>> > synchronizing with C at all.
>> >
>> >   How can one even begin to diagnose this problem? ntpd on A and B is
>> > not dumping any information to my logs. In particular, the "time
>> > reset" messages are absent. For all practical purposes, it is as
>> > though it were not running at all on those two boxes - however,
>> > synchronizing by hand with C by means of ntpdate works fine on both A
>> > and B.
>> >
>> >    Any ideas, anyone?
>>
>> Not without any information. post the output of ntpq -p A B C so we can
>> see at least whether at least they are synchronized.
> 
>    Here's the output from ntpq -p A B C as obtained when executed at A:
> 
> 
> host                remote           refid           st t when poll
> reach   delay   offset  jitter
> =========================================================================================================
> 
> A.mydomain.org   *LOCAL(0)        LOCAL(0)           10 l   58   64
> 377    0.000    0.000   0.004
> A.mydomain.org    C.mydomain 192.83.249.28            3 u  435 1024
> 357    1.741  2646.98 562.826
> 
> host                remote           refid           st t when poll
> reach   delay   offset  jitter
> =========================================================================================================
> 
> B.mydomain.org    LOCAL(0)        LOCAL(0)           10 l   53   64
> 377    0.000    0.000   0.004
> B.mydomain.org   *gabe.kjsl.com   204.123.2.72        2 u   55  256
> 377  226.316   34.622 239.653
> 
> host                remote           refid           st t when poll
> reach   delay   offset  jitter
> =========================================================================================================
> 
> C.mydomain.org    LOCAL(0)        LOCAL(0)           10 l   56   64
> 377    0.000    0.000   0.008
> C.mydomain.org   +gabe.kjsl.com   204.123.2.72        2 u   77  512
> 377  812.788  -91.428  71.546
> C.mydomain.org   *zorro.sf-bay.or 216.218.254.202     2 u   18  512
> 357  539.809  -240.04  89.970
> C.mydomain.org    165.227.227.1   0.0.0.0            16 u    -  256
> 0    0.000    0.000 4000.00
> C.mydomain.org   +zorac.sf-bay.or 204.123.2.5         2 u   19  512
> 377  402.009  -310.04 671.127
> C.mydomain.org    io.berkeley.net 0.0.0.0            16 u   72  256
> 0    0.000    0.000 4000.00
> 
>    There is one change with respect to the setup I described, in that
> host B now gets its synchronization from the same external host as C,
> whereas A still gets its synchronization from C.
> 
>    When I obtained this data, both hosts B and C were staying in sync
> reasonably well (always less than 0.5 seconds) with the external host,
> whereas A had already drifted more than 3 seconds.
> 

You also need to post your ntp.conf files. There is also something wrong
with the output since there seems to be an extra entry at the beginning.

And please don't send just to me personally, use the maiing list. I
won't necessarily be the one to solve your problem.

Danny

Danny



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