[ntp:questions] Clarification Required about NTP

Martin Burnicki martin.burnicki at meinberg.de
Mon Feb 9 13:22:33 UTC 2009

balajisundar at midascomm.com wrote:
> Dear All,
> Currently i am using Red Hat 7.2 Linux PC
> I have 3 Red Hat 7.2 Linux PCs for Testing
> I have using 2 Linux PC as Redundant PC
> I have configured floating IP as NTP Server on 3 Linux PCs
> Floating IP is
> PC1 IP is
> PC2 IP is
> PC3 IP is
> I have Written a script to monitoring the PC1 to PC2 vice-versa every 30
> Seconds
> Assume PC1 is currently Active and its Network is
> goes down or Shutdown the PC1 then the Floating IP will
> be host in PC2 and respectively
> *Clarification Required is*  On this situation whether i need to restart
> the ntp ser
> ver or it will automatically
> take care NTP Server IP Address changes and if its takes automatically
> then how much
> time its take to sync with configured ntp Server

I think the case of NTP is indeed different than other cases where you let
another server take ofer HTTP or email services. This is simply due to the
fact the served time is bound to the specific hardware.

If you have several redundant machines with one fixed, individual address
and a "floating" IP address you should simply configure your NTP clients to
use all the fixed IP addresses, i.e. each of the redundant machines in

If the times on all of them are synchronized to the same level of accuracy
then it should not matter from which one your clients accept the time. If
one of them is way off or even offline then the 2 "good" ones will overvote
the false ticker and have the falseticker be discarded by the clients. 

So this should exactly be what you expect.

Martin Burnicki

Meinberg Funkuhren
Bad Pyrmont

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