[ntp:questions] Re: NTP sync problems

Richard B. Gilbert rgilbert88 at comcast.net
Thu Dec 9 22:24:59 UTC 2004

Robert Rati wrote:

> I'm running NTP 4.2 on a Linux system which syncs off of 2 other Linux 
> boxes (One Debian, other Redhat) running ntp (one is ntp 4.1, other is 
> ntp 4.1.2) and I'm having no problems syncing.
> However, when I use the same client in a different environment which 
> syncs off of a Sun box running NTP 4.2 or a SUSE Linux box running NTP 
> 4.1, I can't sync.  When I run ntpq, I see this:
> [root@ root]# ntpq -pn
>      remote           refid      st t when poll reach   delay   offset 
>  jitter
> ============================================================================== 
> *     LOCAL(0)        10 l   31   64  377    0.000    0.000 
>  0.001
> x<IP>        .LCL.            1 u   35   64  377    0.272  -33.321   
> 2.439
> x<IP>        LOCAL(0)        11 u   44   64  377    0.416  735934.   
> 6.326
> The "x" status means that it is a "designated falseticker by the 
> intersection algorithm".  What does this mean?  Is this a client or 
> server configuration issue?  Can anyone give me some tips on how to 
> debug this situation?
> Rob

You have configured two servers which have wildly different notions of 
what time it is. Both servers are serving their unsynchronized local clocks.

Two servers is the worst possible configuration!  Ntpd knows for certain 
that at least one of these two is "insane" and has every reason to 
suspect that both are.

You can configure an isolated subnet with no external time reference and 
it will synchronize to whatever single server you designate.  It 
probably won't give you close synchronization because the server is 
almost certainly drifting as badly as, or worse than, the clients.  It 
should keep all the systems within a few hundred milliseconds of each 
other but they will not necessarily have the correct time.

If you want the correct time and close synchronization, use either a 
hardware reference clock (GPS receiver, WWV reciever, WWVB receiver, 
etc.) or a group of external network servers that are synchronized to 
such reference clocks.  Four, or more, servers are recommended for 
protection against "falsetickers", hardware failures, and network 
problems. .

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