[ntp:questions] Garmin 18x LVC - degraded precision ?

Brandon Applegate brandon at burn.net
Wed Aug 7 00:37:44 UTC 2019

Hello all,

First of all - I know my question technically isn’t about ntp software per se.  But I figured this is probably the best audience that might know what’s going on.

I have a Garmin 18x LVC connected via serial to a Linux box.  It has been rock solid for years (I think I got it in 2012 ?).  I have all the usual tweaks for low_latency, recommended ntp.conf fudge values, flags, etc.  I’ve also used the SNSRCFG Windows software to update the firmware as well as make tweaks (i.e. minimum GPS sentence output).  It has been very accurate for years (i.e. in the single digit microseconds, typically close to 0).

In the past couple of weeks (maybe, regretfully I don’t have my graphing running at the moment…) it seems to have crept up into the 20s.

    remote           refid      st t when poll reach   delay   offset  jitter
o127.127.20.0    .GPS.            0 l    3   16  377    0.000   -0.025   0.005

One thing I notice is that the badformat counter for clockvar is also increasing, whereas I don’t think it really ever increased before:

vom at ice:~$ ntpq -c cv | grep badformat
poll=1508, noreply=1, badformat=865, baddata=0, fudgetime2=600.000,

I haven’t made any software or config changes.  The GPS puck hasn’t been moved.  I’ve rebooted the server as well as power cycled the puck.  I’m not quite sure what else I can look at.

Could it be my 18x is “dying a slow death” ?  Has anyone ever seen this behavior or have any advice ?

Thanks in advance.

Brandon Applegate - CCIE 10273
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