[ntp:questions] Can't Understand NTP behaviour,

Pranay Kumar Srivastava Pranay.Shrivastava at hcl.com
Fri Jun 24 06:45:47 UTC 2011


In our NTP client-server setup which is done locally, we've 3 servers each made to synchronize with its own local clock only.

The client is having the entries of these 3 servers. The following is the output snippet of ntpq -p taken over a period of 1 hour at regular intervals of 5 seconds.

     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
 10.58.80.9      .STEP.          16 u   66   64    0    0.000    0.000   0.001
 10.58.80.3      .STEP.          16 u  272   64    0    0.000    0.000   0.001
 10.58.80.65     LOCAL(0)         6 u   11   64    1    0.279  -144779   0.001
 LOCAL(0)        .LOCL.          10 l    3   16    1    0.000    0.000   0.001


     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
 10.58.80.9      LOCAL(0)         4 u  192   64    3    0.261  144785.   0.330
 10.58.80.3      LOCAL(0)        11 u  164   64    3    0.261  2183.05   4.762
 10.58.80.65     LOCAL(0)         6 u  191   64    3    0.263   -1.117   0.689
*LOCAL(0)        .LOCL.          10 l  156   16   77    0.000    0.000   0.001


     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
x10.58.80.9      LOCAL(0)         4 u   13   64   17    0.320   -1.480   0.638
*10.58.80.3      LOCAL(0)        11 u    2   64   17    0.248  -142506  10.778
 10.58.80.65     LOCAL(0)         6 u   38   64    7    0.245  -144793   0.993
 LOCAL(0)        .LOCL.          10 l   15   16  377    0.000    0.000   0.001


     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
*10.58.80.9      LOCAL(0)         4 u  170   64   17    0.339  144797.   0.612
x10.58.80.3      LOCAL(0)        11 u  188   64   17    0.248  2385.51  10.642
x10.58.80.65     LOCAL(0)         6 u  147   64   37    0.210   -3.332   1.887
 LOCAL(0)        .LOCL.          10 l  154   16  377    0.000    0.000   0.001



     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
x10.58.80.9      LOCAL(0)         4 u    1   64   37    0.316   -1.978   0.782
x10.58.80.3      LOCAL(0)        11 u   26   64   37    0.212  -142314  13.185
*10.58.80.65     LOCAL(0)         6 u   53   64   37    0.197  -144806   2.011
 LOCAL(0)        .LOCL.          10 l    4   16  377    0.000    0.000   0.001


     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
*10.58.80.9      LOCAL(0)         4 u  197   64   77    0.318  144810.   0.976
x10.58.80.3      LOCAL(0)        11 u  208   64   77    0.209  2567.32  16.049
x10.58.80.65     LOCAL(0)         6 u  148   64  177    0.277   -4.718   2.614
 LOCAL(0)        .LOCL.          10 l  160   16  377    0.000    0.000   0.001




The client chooses the server with a high value of offset initially. Then, when the offset lowers down, it discards it as a falseticker but chooses another server with high offset value. Why is this toggle taking place and the synchronization is being done with a server having high offset value any reason for this?

Ntpdate wasn't run on the client before starting the ntp daemon. It's not possible for us to run ntpdate on the client that's one of the constraints. Please advise on this behaviour of ntp.


Regards,
Pranay Kr. Srivastava
pranay.shrivastava at hcl.com
Software Engineer
ERS,HCL Technologies
A-5, Sector 24, Noida 201301, U.P. (India)


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