[ntp:questions] Accept high root dispersion from Windows NTP server

Lucas van Braam van Vloten lucas2 at dds.nl
Fri Jul 10 13:09:29 UTC 2015


Hi list,

I am running ~30 Linux servers (RHEL6) which synchronize their time
against the NTP server on two Windows 2008 Domain Controllers.

My Linux clients can see the time servers, but association is rejected.
I believe that this is due to a very high root dispersion on these
servers, namely around 10s.

I have talked to the Windows administrator, and according to him this
high root dispersion has something to do with the server running on a VM
(VMWare). He says that it does not make the server a less reliable time
source, and that it cannot be solved on the Windows server. "We just
have to live with it" (his words)

However, my Linux NTP clients keep rejecting the association.

Is there a way in the NTP client configuration to ignore the root
dispersion value of the server in the decision whether to associate?
Or, alternatively, can I adjust the threshold for what is accepted, for
example to 15 seconds or so?

This is the output on my Linux machine:
  
ntpq> associations

ind assid status  conf reach auth condition  last_event cnt
===========================================================
  1 61931  9024   yes   yes  none    reject   reachable  2
  2 61932  9024   yes   yes  none    reject   reachable  2

ntpq> rv 61931
associd=61931 status=9024 conf, reach, sel_reject, 2 events, reachable,
srcadr=puhtdc0001.piaddot.prorail.nl, srcport=123, dstadr=172.24.75.21,
dstport=123, leap=00, stratum=2, precision=-6, rootdelay=31.250,
rootdisp=11071.594, refid=172.24.70.105,
reftime=d94a40a7.f1dcccf5  Fri, Jul 10 2015 15:01:27.944,
rec=d94a4115.dcbd0077  Fri, Jul 10 2015 15:03:17.862, reach=377,
unreach=0, hmode=3, pmode=4, hpoll=6, ppoll=6, headway=56,
flash=400 peer_dist, keyid=0, offset=16.847, delay=0.662,
dispersion=16.516, jitter=8.528, xleave=0.043,
filtdelay=     0.66    0.72    0.45    0.72    0.41    0.56    0.63
0.43,
filtoffset=   16.85   28.33   19.69   27.05   31.19   22.19   22.18
15.32,
filtdisp=     15.63   16.62   17.61   18.58   19.54   20.55   21.52
22.50
ntpq> rv 61932
associd=61932 status=9024 conf, reach, sel_reject, 2 events, reachable,
srcadr=puhtdc0002.piaddot.prorail.nl, srcport=123, dstadr=172.24.75.21,
dstport=123, leap=00, stratum=3, precision=-6, rootdelay=62.500,
rootdisp=11128.265, refid=172.24.75.30,
reftime=d94a404a.0c65965c  Fri, Jul 10 2015 14:59:54.048,
rec=d94a4114.de3c9281  Fri, Jul 10 2015 15:03:16.868, reach=377,
unreach=0, hmode=3, pmode=4, hpoll=6, ppoll=6, headway=54,
flash=400 peer_dist, keyid=0, offset=12.680, delay=0.733,
dispersion=16.513, jitter=9.014, xleave=0.025,
filtdelay=     0.73    0.80    0.67    0.63    0.66    1.17    7.34
0.68,
filtoffset=   12.68   17.04   14.66   13.59   19.40   19.83   28.60
26.65,
filtdisp=     15.63   16.62   17.59   18.55   19.56   20.55   21.54
22.51

Any help would be greatly appreciated!

Kind regards,
Lucas



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