Hi folks,
I have a problem with a GPS device. It is flagged "falsetick" by ntpd. It
worked well for a few days but it stays as a falseticker since "Jun 23
14:19:15".
I have 2 devices in LAN:
- the device 1 (192.168.1.1) has a GPS (GARMIN G-16x HVS) connected to it and a
ntpd server with this configuration:
tinker panic 0
server 127.127.20.0 mode 1 prefer
fudge 127.127.20.0 flag1 1 flag2 0 flag3 1 time2 0.600
statistics peerstats loopstats
statsdir /var/log
filegen peerstats file ntpd.peers.log type none nolink enable
filegen loopstats file ntpd.loops.log type none nolink enable
- the device 2 (192.168.1.3) has a ntpd server with this configuration:
tinker panic 0
server 192.168.1.1 iburst
statistics peerstats loopstats
statsdir /var/log
filegen peerstats file ntpd.peers.log type none nolink enable
filegen loopstats file ntpd.loops.log type none nolink enable
With ntpq software, I've got these information about the ntp server 192.168.1.1:
---------------------------------------------
# ntpq 192.168.1.1
ntpq> pe
remote refid st t when poll reach delay offset jitter
==============================================================================
xGPS_NMEA(0) .GPS. 0 l 21 64 377 0.000 -93.417 0.019
ntpq> as
ind assid status conf reach auth condition last_event cnt
===========================================================
1 19198 9144 yes yes none falsetick reachable 4
ntpq> rv 19198
associd=19198 status=9144 conf, reach, sel_falsetick, 4 events, reachable,
srcadr=GPS_NMEA(0), srcport=123, dstadr=127.0.0.1, dstport=123, leap=00,
stratum=0, precision=-20, rootdelay=0.000, rootdisp=0.000, refid=GPS,
reftime=dd07801f.17eafe6a Wed, Jul 5 2017 17:11:27.093,
rec=dd078020.30f1b22b Wed, Jul 5 2017 17:11:28.191, reach=377,
unreach=0, hmode=3, pmode=4, hpoll=6, ppoll=6, headway=0, flash=00 ok,
keyid=0, ttl=1, offset=-93.417, delay=0.000, dispersion=0.941,
jitter=0.019,
filtdelay= 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00,
filtoffset= -93.42 -93.41 -93.41 -93.41 -93.41 -93.41 -93.39 -93.38,
filtdisp= 0.02 0.98 1.94 2.90 3.86 4.82 5.78 6.74
ntpq> clockvar
associd=0 status=00f2 15 events, clk_bad_format,
device="NMEA GPS Clock",
timecode="$GPRMC,151202,A,4649.1519,N,00630.1749,E,002.1,352.5,050717,001.3,E*7A",
poll=19345, noreply=18, badformat=8950, baddata=0, fudgetime2=600.000,
stratum=0, refid=GPS, flags=5
---------------------------------------------
As you can see, the source GPS_NMEA is flagged "falsetick". And, I don't
understand why. I read the page
https://www.eecis.udel.edu/~mills/ntp/html/select.html and several posts in the
mailing list but I don't find relevant information for my case. We can see
"clk_bad_format" status in the clockvar command return. Can be an explanation
of the falsetick or there is a cryptic value that is too high that I need to
mitigate with tos mindist or something like that ?
Maybe the GPS didn't receive some NMEA packets at one point (I put the GPS
device inside my home while it was raining). Can be an explanation why ntpd
think is not a reliable time source since then ? The GPS device has a clear
view now but nothin change. The source remains a falseticker.
When a source is flagged flaseticker, can it not become a truechimer again ?
I would appreciate some advices about this problem.
Regards,
Anthony.
--
----------------------------------------------------------
Viallard Anthony <[email protected]>
[ Embedded System | Software Engineer ]
----------------------------------------------------------
Syscom Instruments SA
Rue de l'industrie 21
1450 Sainte-Croix
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