[ntp:questions] What exactly does "Maximum Distance Exceded" mean?
joegwinn at comcast.net
Fri Mar 13 04:31:11 UTC 2009
I have been debugging some system problems. The main system is too
complicated, with too many people doing too many things, so I sought
quiet refuge in an isolated test system consisting of a NTP timeserver
connected by a point-to-point ethernet cable to a computer running NTP,
which generates peerstats and loopstats data. This test system is
air-gap isolated from the rest of everything. Only one timeserver is
available to a given computer at a time.
The timeserver can be either a Symmetricom ET6010 GPS receiver feeding
an IRIG-B002 time signal to a Symmetricom TS2100 Network Time Server, or
a Spectracom 9383 NTP timeserver with built-in GPS receiver. The GPS
receivers are driven from a common antenna via a splitter.
The computer can be a Sun Ultra 10 or a Sun Ultra 60, in both cases
running Solaris 9. Solid boxes, but old. The OS version reply is SunOS
5.9 Generic May 2002. This was clean installed from CD a week ago, so
has not had time to collect too many barnicles.
NTP version 3 is running. I've been trying to find the command to give
me the full version, including dot (like 3.4y), and I get answers, but
don't know which one to believe, and if the version given is that of the
NTP daemon itself, or of ntpq, or of ntpdate.
The full grid of four tests, being two timeservers by two computers, has
been run. Many odd things are seen, but the question for today is about
status codes in peerstats file records.
Most of the replies that NTP is using to update the time have a status
code of 9514, which translates to the following:
Configured, reachability OK; Current sync source - max distance
exceeded; Count is 1; Peer now reachable.
The part that has me most perplexed is the "max distance exceeded" part,
as this is a direct wired connection, with zero hops, zero delay, and no
interfering traffic. Obviously, they are not talking about physical
distance or hops or the like, so the "distance" has to have units of
Although most received replies have status 9514, they are nonetheless
used to update the loop filter and so appear in the loopstats file.
When I co-plot loopstats and peerstats, the loopstats dots land on top
of the peerstats dots.
What is this error likely telling me? What are the possibilities? What
tests will tell the tale?
Thanks to all,
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