[ntp:questions] reachability register

Charles Elliott elliott.ch at comcast.net
Thu Apr 9 12:24:04 UTC 2015


	All I can say is, it does that sometimes.  I think what might be
happening is that ntpq caught ntpd before the reachability register was
updated, although it updates that fairly early in the game.  You can see the
code in proto.c in a recent source distribution, like here:



MD5 sum:


	If you want to see it work correctly and you are using Windows,
start the Meinberg NTP Monitor and set it to monitor your Internet-facing
NTP client.  On a non-Windows O/S, just use the host command to set ntpq to
the Internet-facing NTP client and repeatedly send it the peers command.

	In any case, then unplug your Internet modem and your router.  Wait
a few seconds (~60), plug the modem back in, then after a few seconds (~30)
plug in your router.  Then watch the Meinberg NTP Monitor or the ntpq peers
output of the reachability register.  You should see something like the

 Binary    Octal
  1000000	100
 10000001	201
       11	  3
      111     7
     1111 	 17
    11111  	 37
   111111	 77
  1111111	177
 11111111	377

Charles Elliott

> -----Original Message-----
> From: questions [mailto:questions-
> bounces+elliott.ch=comcast.net at lists.ntp.org] On Behalf Of MAYER Hans
> Sent: Wednesday, April 8, 2015 9:23 AM
> To: questions at lists.ntp.org
> Subject: [ntp:questions] reachability register
> Dear all,
> I have a question about the reachability register. For my opinion this
> is a left shift 8-bit register.
> I looked in one of our internal ntp-server with "ntpq" and found a
> value of 376 to a peer configured internal server. After waiting the
> time difference between "poll" and "when" I can find the value of 377.
> How is it possible ? For my understanding this could only happen after
> 8 times the poll interval. The next value should be 375 and after that
> 373. And so on shifting the 0-bit to the left.
> Kind regards
> Hans
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