I'm not very knowledgeable about NTP, but I'm suspicious of its
implementation on one of my servers. I have one server running the
Debian sarge package of NTP:
cn2:/var/log# ntpq
ntpq> version
ntpq [EMAIL PROTECTED]:4.2.0a+stable-2-r Fri Aug 26 10:30:19 UTC 2005 (1)
ntpq>
I've tried to set this server up as a timeserver for my network, using
tock.usno.mil, a time server at my institution (Johns Hopkins
University) and the pool timeservers:
ntpq> peers
remote refid st t when poll reach delay offset
jitter
========================================================================
======
+jhname.hcf.jhu. 128.4.1.1 2 u 60 64 177 3.313 835.818
545.232
*ntp1.usno.navy. .USNO. 1 u 60 64 177 8.567 827.174
551.616
+trane.wu-wien.a 195.13.1.153 3 u 57 64 177 125.292 841.188
548.251
+221-15-178-69.g 140.142.16.34 2 u 50 64 177 107.300 1212.00
395.490
+tock.jrc.us 207.168.62.76 2 u 58 64 177 16.942 1020.49
432.251
LOCAL(0) LOCAL(0) 13 l 55 64 177 0.000 0.000
0.002
ntpq>
I notice the problem here, and if I run 'watch ntpq -p.' Seldom is my
reachability 377, and it frequently and inexplicitly drops to 1 as I'm
watching it. Ten minutes ago reachability was 177 as shown above.
Watching it in the last minute, it dropped from 377 to 1 on all sources.
Now it's:
Every 2s: ntpq -p
Fri Dec 8 10:35:18 2006
remote refid st t when poll reach delay offset
jitter
========================================================================
======
jhname.hcf.jhu. 128.4.1.1 2 u 53 64 3 2.707 660.049
176.587
ntp1.usno.navy. .USNO. 1 u 52 64 3 8.904 663.193
181.873
trane.wu-wien.a 195.13.1.153 3 u 49 64 3 125.979 681.070
186.182
221-15-178-69.g 140.142.16.34 2 u 51 64 3 104.207 485.281
183.834
tock.jrc.us 207.168.62.76 2 u 50 64 3 16.912 668.565
186.520
LOCAL(0) LOCAL(0) 13 l 49 64 3 0.000 0.000
0.002
Is this normal behavior for NTP, to frequently lose the ability to reach
a timeserver? If not, how can I troubleshoot it further?
Here's the syslog entries pertaining to npt for just one hour this
morning:
Dec 8 09:03:06 cn2 ntpd[16955]: time reset +3.120367 s
Dec 8 09:07:21 cn2 ntpd[16955]: synchronized to LOCAL(0), stratum 13
Dec 8 09:08:25 cn2 ntpd[16955]: synchronized to 67.128.71.75, stratum 2
Dec 8 09:09:31 cn2 ntpd[16955]: synchronized to 192.5.41.41, stratum 1
Dec 8 09:23:33 cn2 ntpd[16955]: time reset +3.503628 s
Dec 8 09:27:51 cn2 ntpd[16955]: synchronized to LOCAL(0), stratum 13
Dec 8 09:28:56 cn2 ntpd[16955]: synchronized to 192.5.41.41, stratum 1
Dec 8 09:36:18 cn2 ntpd[16955]: synchronized to 128.220.2.7, stratum 2
Dec 8 09:36:25 cn2 ntpd[16955]: synchronized to 192.5.41.41, stratum 1
Dec 8 09:40:40 cn2 ntpd[16955]: synchronized to 128.220.2.7, stratum 2
Dec 8 09:41:45 cn2 ntpd[16955]: synchronized to 192.5.41.41, stratum 1
Dec 8 09:41:47 cn2 ntpd[16955]: synchronized to 69.178.15.221, stratum
2
Dec 8 09:43:46 cn2 ntpd[16955]: synchronized to 192.5.41.41, stratum 1
Dec 8 09:49:21 cn2 ntpd[16955]: synchronized to 67.128.71.75, stratum 2
Dec 8 09:49:21 cn2 ntpd[16955]: time reset +4.512453 s
Dec 8 09:53:41 cn2 ntpd[16955]: synchronized to LOCAL(0), stratum 13
Dec 8 09:54:39 cn2 ntpd[16955]: synchronized to 128.220.2.7, stratum 2
Dec 8 09:54:44 cn2 ntpd[16955]: synchronized to 192.5.41.41, stratum 1
Dec 8 10:01:11 cn2 ntpd[16955]: synchronized to 67.128.71.75, stratum 2
Dec 8 10:02:14 cn2 ntpd[16955]: synchronized to 192.5.41.41, stratum 1
Dec 8 10:09:40 cn2 ntpd[16955]: synchronized to 67.128.71.75, stratum 2
Dec 8 10:10:51 cn2 ntpd[16955]: synchronized to 192.5.41.41, stratum 1
Dec 8 10:10:51 cn2 ntpd[16955]: time reset +3.950081 s
Dec 8 10:15:08 cn2 ntpd[16955]: synchronized to LOCAL(0), stratum 13
Dec 8 10:16:14 cn2 ntpd[16955]: synchronized to 192.5.41.41, stratum 1
These time resets seem rather large to me. Is this normal, too?
Here's the output of the peerstat.qwk script:
cn2:/var/log/ntpstats# gawk -f
/home/kevinz/ntp-4.2.2p4/scripts/stats/peer.awk peerstats
ident cnt mean rms max delay dist
disp
========================================================================
==
67.128.71.75 715 2364.263 996.393 2364.263 16.751 947.994
96.315
127.127.1.0 844 0.000 0.000 0.000 0.000 0.990
0.957
192.5.41.41 728 2321.937 1023.300 2964.896 7.907 944.371
94.581
137.208.3.51 675 2500.134 995.134 3013.699 124.989 503.205
44.951
128.220.2.7 721 2405.904 982.298 2712.599 2.564 940.869
95.476
69.178.15.221 722 2395.872 1002.130 2911.691 104.730 997.703
95.423
cn2:/var/log/ntpstats#
Are there any other diagnostics that I could run to help identify any
problem?
Thank you all for your help, advice and suggestions.
-Kevin
Kevin Zembower
Internet Services Group manager
Center for Communication Programs
Bloomberg School of Public Health
Johns Hopkins University
111 Market Place, Suite 310
Baltimore, Maryland 21202
410-659-6139
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