[ntp:questions] Output of ntpq -p regarding stratum level
unruh-spam at physics.ubc.ca
Wed Sep 10 22:49:06 UTC 2008
Stefan.Nottorf at plath.de (Nottorf, Stefan) writes:
>although this is probably a beginner's question, I would like to
>understand this before I run into trouble caused by misunderstanding
>basic information. I think i misunderstood how to read the output of
>The third column ("st") shows the stratum.
>But beginning to monitor time synchronization in our network, I noticed
>a slight difference in the understanding of stratum levels between me
>and the monitoring tool (Nagios).
>When I use ntpq -p on one of our hosts I get the following output:
>remote refid st t when poll reach delay offset jitter
>*10.x.y.z .PPS. 1 u 338 1024 377 0.454 -1.559 0.078
>name1.name 10.x.y.z 2 u 471 1024 376 0.209 1.763 0.093
>name2.name 10.x.y.z 2 u 1461 1024 374 0.001 2.652 0.206
>name3.name 10.x.y.z 2 u 596 1024 376 0.385 0.052 0.322
>LOCAL(0) .LOCL. 5 l 59 64 377 0.000 0.000 0.001
>Until now I read this line :*10.x.y.z .PPS. 1 u 338 1024 377
>0.454 -1.559 0.078
>the following way:
>The host I ran ntpq -p on is synchronized to (*) server 10.x.y.z., whose
>time source is a PulsePerSecond clock. 10.x.y.z is a server at stratum 1
>and 338 seconds have passed since the last poll. The poll interval is
The PPS clock is stratum 0. The host synced to that is stratum 1. The host
synced to a stratum 1 is stratum 2, etc.
>Because the time reference is located at stratum 1, this host is located
>at stratum 2.
>Similarily, if I look at server name1.name: name1.name is a server
>located at stratum 2 and is itself synchronized to server 10.x.y.z.
>If this is correct so far, the following output confuses me. I ran a
>check for time synchronization for Nagios. Nagios provides a couple of
>checks, one of them called check_ntp_peer. I use it to detect
>differences between expected and current stratum levels.
>/<installation_path>/libexec/check_ntp_peer -H name1.name -W 4 -C 6 -v
>1 candiate peers available
>synchronization source found
>Getting offset, jitter and stratum for peer 4551
>parsing offset from peer 4551: -0.001193
>parsing stratum from peer 4551: 1
>NTP OK: Offset -0.001193 secs,
>This output tells me, that name1.name is located in stratum 1 (instead
>of the expected stratum 2).
This is an issue with nagios.
>In short: does the column st refer to the stratum of the remote host OR
>does it mean "If I synchronize to that remote host I will get to stratum
As you can see, the machine that is synced to the pps is stratum 1 .
>Thanks and regards,
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