[ntp:questions] Side effects of using prefer on server?

Markus Schöpflin no.spam at spam.spam
Fri Sep 16 14:22:43 UTC 2011

Replying to myself...

Am 14.09.2011 14:20, schrieb Markus Schöpflin:


> Given the following configuration on the client:
> ---%<---
> # driftfile
> driftfile /var/lib/ntp/drift
> # keys
> trustedkey 1
> requestkey 1
> keys /etc/ntp/keys
> # server
> server WRB1 version 4 iburst minpoll 5 maxpoll 5 prefer
> server WRB2 version 4 iburst minpoll 5 maxpoll 5
> --->%---
> I'm observing that when the preferred server becomes unreachable, it takes a
> really long time to switch to the second server:


This behaviour definitely has changed from ntpd 4.2.2p1 to 4.2.6p3.

With 4.2.2p1 the client using the above mentioned configuration synchronized 
to the server WRB2 226 seconds (round about seven times the fixed poll 
interval of 32 seconds) after server WRB1 was stopped. This is about the same 
time as the client decided that WRB1 was unreachable.

Using 4.2.6p3 it took the client 272 seconds (about 8 times the poll interval) 
to realize that the server WRB1 is unreachable, but only 962 seconds later (!) 
it finally reported WRB2 as the new peer.

Is the behaviour of 4.2.6p3 to be considered a bug or am I completely off the 
track here?


More information about the questions mailing list