[ntp:questions] Re: ntp server 'rejected'
ronan at noc.ulcc.ac.uk
Wed Apr 19 17:05:51 UTC 2006
david.sanderson at bem.fki-et.com wrote:
> The linux box shows:
> ntpq> rv 53013
> assID=53013 status=9614 reach, conf, sel_sys.peer, 1 event,
> srcadr=172.16.151.4, srcport=123, dstadr=172.16.20.117, dstport=123,
> leap=00, stratum=1, precision=-20, rootdelay=0.000,
> rootdispersion=996.750, refid=GPS, reach=377, unreach=0, hmode=3,
Similar rootdispersion, then.
> >> I can see nothing suspicious here, apart from sync_telephone possibly?
Upon further investigation reference clocks using the shared-memory
driver are always marked sync_telephone.
> >That, and there's the rootdispersion again. What does "ntpq -crv 21093"
> >show? (adjust for current peer assoc id).
> This is on the NTP Server:
> ntpq> rv 21093
> status=96f4 reach, conf, sel_sys.peer, 15 events, event_reach,
> ntpq> srcadr=SHM(1), srcport=123, dstadr=127.0.0.1, dstport=123,
> stratum=0, precision=1700881256, rootdelay=0.000, rootdispersion=0.000,
That precision figure is nonsense.
> refid=GPS, reach=377, unreach=0, hmode=3, pmode=4, hpoll=4, ppoll=4,
> flash=00 ok, keyid=0, ttl=0, offset=0.001, delay=0.000,
> dispersion=996.348, jitter=0.002,
> reftime=c7f0c2e1.ffffeed9 Wed, Apr 19 2006 14:08:33.999,
> org=c7f0c2e1.ffffeed9 Wed, Apr 19 2006 14:08:33.999,
> rec=c7f0c2e2.24c8cd63 Wed, Apr 19 2006 14:08:34.143,
> xmt=c7f0c2e2.24c79f66 Wed, Apr 19 2006 14:08:34.143,
> filtdelay= 0.00 0.00 0.00 0.00 0.00 0.00 0.00
> filtoffset= 0.00 0.00 0.00 0.00 0.00 0.00 0.00
> filtdisp= 1000.00 1000.27 1000.53 1000.80 1001.04 1001.28 1001.52
> Is this just the dispersion forn the GPS source? It doesnt have a very
> good view
> of the sky, but the diagnostics claim all is healthy and ok, and the
> Linux box
> isnt complaining...
I think that says more about the Linux box than the server.
Those dispersion figures also look iffy.
> >What is your GPS clock? Is this a Galleon NTP server, by any chance?
> >I see similar behaviour with what I have been told is one of those,
> >from an ntp-4.0.99k client.
On which I see
% ntpdc -nc "pstats x.x.x.x"
remote host: x.x.x.x (details not relevant)
local interface: y.y.y.y
time last received: 928s
time until next send: 97s
reachability change: 2790983s
packets sent: 3889
packets received: 3346
bad authentication: 0
bogus origin: 0
bad dispersion: 580833 <====
bad reference time: 0
candidate order: 0
Unfortunately that statistic is not gathered in later versions.
> It is a Galleon NTP Server. The QNX claims:
> version="ntpd 4.1.1 at 1.786 Thu Mar 27 11:18:57 EST 2003 (3)" in its rv.
> but the linux is much newer:
> version="ntpd 4.2.0a at 1.1190-r Thu Apr 14 07:47:25 EDT 2005 (1)"
> Interestingly I have an x86 based QNX box which seems to sync and then
> lose sync periodically. An extract from its ntplog.txt:
What version of ntpd is that box running?
One thing you might try is marking the server prefer in ntp.conf, eg
server 172.16.151.4 prefer
Failing that (or anyone else's input ...) maybe the newer ntpd is
just more forgiving of "high" rootdispersion, so you might have no
choice but to upgrade ntpd to a later version.
(One thing I notice was changed in 4.2.0 from earlier versions,
in ntp_proto.c the comparison to root_distance changes from
root_distance(peer) >= MAXDISTANCE + 2 * ...
root_distance(peer) >= MAXDISTANCE + 2. * ...
Was that actually a bug-fix?)
Ronan Flood <R.Flood at noc.ulcc.ac.uk>
working for but not speaking for
Network Services, University of London Computer Centre
(which means: don't bother ULCC if I've said something you don't like)
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