I was checking the stability of a new USB GPS refclock on a server which is configured to use the GPS, servers from the ntp pool, and another server of mine that has a PPS GPS receiver.
I noticed that almost all the pool servers had disappeared. I then checked other machines that use my "good" server and the ntp pool; most all of the pool servers had also disappeared on those machines. This is a mix of PC linux, rasberry pi linux, rasberry pi buster, and Windows 10 machines with Meinberg, all with the latest ntp from their distros. Long story short: I realized I had had a network outage and tested the theory that was the cause. It was. It seems that any server in ntp.conf that is specified as a name, as the pool servers are, will after a sufficiently long DNS outage just disappear and not come back after the outage without restarting ntp. It would seem to me that ntp should only need to do a DNS lookup on startup and from then on continue to use the address found. But that is not how ntp works. Anyway, the bottom line is that if the pool is your only source of time and if there is a DNS failure for a sufficiently long time, you will lilely not have any source of time afterwards. As for the USB GPS I was testing, it is called a VK-162 G-Mouse available from Amazon for $14, uses the Windows 10 native driver so it works with Meinberg ntp, and keeps the time within single digit milliseconds without any other servers. _______________________________________________ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
