[ntp:questions] debugging strange ntp in virtual environment

Harlan Stenn stenn at ntp.org
Wed Sep 18 20:45:31 UTC 2013


"Riccardo Castellani" writes:
> My NTP server has strange problem and my clients cannot update their time 
> clock.
> My NTP server is Linux and NTP version is 4.2.0.a

That's 10 years old, and 3 (coming up on 4) major releases ago.

http://support.ntp.org/Dev/ReleaseTimeline 

> This NTP server is a virtual machine (by P2V) but few months ago it was 
> working fine.
> My clients get following msg when I run ntpd daemon: 'no server suitable for 
> synchronization found'
> In client 'A' I run this command 'ntpq -pn' :
> 
>      remote           refid      st t when poll reach   delay   offset 
> disp
> =============================================================================
> =
>  myntpserver    0.0.0.0         16 u   29   64    0     0.00    0.000 
> 16000.0

client A is not getting any packets exchanged with myntpserver.

> In client 'B' I run this command 'ntpq -pn' :
>      remote           refid      st t when poll reach   delay   offset 
> disp
> =============================================================================
> =
> myntpserver    83.84.69.80     16 u   38   64    0     2.78  -758.11 16000.0

Ditto - your "reach" value is 0.

> In NTP server 'ntpq -pn' shows:
> 
>      remote           refid      st t when poll reach   delay   offset 
> jitter
> =============================================================================
> =
> *193.204.114.232 .CTD.            1 u   22   64  375   20.863  -672.31 
> 232.744
> +193.204.114.233 .CTD.            1 u   22   64  377   20.846  -884.47 
> 178.639
> +193.79.237.14   .PPS.            1 u   17   64  377   26.264  -819.79 
> 181.462
> x192.93.2.20     .GPSi.           1 u   16   64  377   32.996  -1039.3 
> 262.130
> +131.188.3.221   .DCFp.           1 u   22   64  377   42.731  -818.20 
> 179.726

Those offsets fluctuate over 360 msec - that's a lot.  The jitter is
high too.

> I reset drift file, I restarted daemon but 'offset' value increases in few 
> hours until to be 800-1000.

Yes, it's still trying to figure out the drift of your clock.

> In NTP server 'ntpq -c rv' shows:
> 
> assID=0 status=c6f4 sync_alarm, sync_ntp, 15 events, event_peer/strat_chg,
> version="ntpd 4.2.0a at 1.1196-r Fri May 12 09:51:35 EDT 2006 (1)"?,
> processor="i686", system="Linux/2.6.11-1.1369_FC4smp", leap=11,
> stratum=16, precision=-18, rootdelay=0.000, rootdispersion=197.910,
> peer=18845, refid=STEP,
> reftime=00000000.00000000  Thu, Feb  7 2036  7:28:16.000, poll=6,
> clock=0xd5e45b57.a691d9b1, state=2, offset=0.000, frequency=0.000,
> noise=775.898, jitter=238.455, stability=0.000
> 
> 
> I installed another server (this time physical server) in the same lan, 
> configured in the same way, same ntp version and it works fine!!!
> It's physical server, unique difference ! Clients can update time from 
> physical server and no update from the virtual server !
> 
> In physical server  'ntpq -pn' shows:
> 
>      remote           refid      st t when poll reach   delay   offset 
> jitter
> =============================================================================
> =
> *193.204.114.232 .CTD.            1 u  216  512  335   22.177   -4.268 
> 0.244
> +193.204.114.233 .CTD.            1 u   98  512  331   20.756   -4.873 
> 0.351
> -131.188.3.221   .DCFp.           1 u  201  512  335   49.258  -12.984 
> 2.276
> +193.79.237.14   .PPS.            1 u  203  512  335   27.570   -5.418 
> 1.051

Much better offset and drift values.  But you seem to be losing about 2
out of every 8 NTP polls, based on the "reach" numbers.

> In physical server 'ntpq -c rv' shows:
> 
> assID=0 status=0644 leap_none, sync_ntp, 4 events, event_peer/strat_chg,
> version="ntpd 4.2.0a at 1.1196-r Fri May 12 09:51:35 EDT 2006 (1)"?,
> processor="i686", system="Linux/2.6.11-1.1369_FC4smp", leap=00,
> stratum=2, precision=-17, rootdelay=22.177, rootdispersion=35.682,
> peer=64524, refid=193.204.114.232,
> reftime=d5e45b36.ce35610a  Wed, Sep 18 2013 19:02:46.805, poll=9,
> clock=0xd5e45c4d.f6807bbb, state=4, offset=-4.293, frequency=8.223,
> noise=0.823, jitter=0.951, stability=40.108

H


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