[ntp:questions] Different behavior between ntpd 4.2.0 and 4.2.4?

David Woolley david at ex.djwhome.demon.co.uk.invalid
Sat Oct 4 14:45:27 UTC 2008

Johnny Ljunggren wrote:
> I just upgraded som e machines from Mandriva 2006 to 2008 and thus
+ ntpd from 4.2.0 to 4.2.4. Using the exact same ntp.conf file I get
+ different behavior on the two versions, and the 4.2.4 version does not
+ work as expected. I also downloaded the 4.2.4p5 source from ntp.org and
+ installed but got the same behavior.

> LAN connections ok, and restart of ntpd. I let ntpd sync and see with
+ ntpq -c peers that server nanna is in use. If I disconnect the lan
+ connection to nanna eventually ntpq -c peers shows that local clock is
+ being used. However, if I connect the lan to nanna again ntpq -c peers
+ shows that nanna is never accepted as ntp server, and local clock is
+ used no matter how long I wait.
> Doing the same with ntpd 4.2.0 automatically reinstates nanna as ntp

Interesting.  If there is such a difference, it might explain why we are 
getting more reports of machines locking onto local clocks.

Some basic rules.

Never configure a local clock on a pure client and only configure one on 
a server if you understand the tradeoffs.  Even without it, the clock 
frequency will continue to be corrected during a server outage.

If you configure a local clock, ensure that you have enough real servers 
configured to completely outvote it.  That is your basic problem here.

Also, I hope you own nanna, as using minpoll 4 on a public server is 
likely to result in a kiss of death. You may want to review the "Slow 
convergence" thread to see if your reason for overriding the poll limits 
possibly is similar to the one that Dave Mills considers to take the 
application outside the scope of NTP.

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