[ntp:questions] Re: Referencing Outside NTP Server in my Environment.

Richard B. Gilbert rgilbert88 at comcast.net
Tue Aug 1 16:18:59 UTC 2006

vb wrote:

> Hi,
> Configured NTP on HP, HP TRU64, Linux and Solaris servers. Each group
> has NTP Server and configured local clock impersonator and is
> referenced in NTP clients.Works good.
> Question is ,  Can I reference some outside NTP server, like defense or
> any Educational institute to the NTP servers I configured so that in
> case of a problem, all the clients will be synchronized to that of the
> otside server instead of local clock impersonator . We not have Radio
> Receivers and have firewalls.
> Thanks for your response in advance.
> -Venkat

What, exactly, is a "local clock impersonator"?

If you can reference some outside NTP server, you should.

The simplest configuration is to designate one internal system as an NTP 
server and configure that system to use one external server.  Your local 
server will then synchronize to the external server and all your local 
clients will synchronize to your internal server.

That is not the best configuration, just the simplest.  The weakness is 
that both the external and internal server are each single points of 
failure.  If either one fails your clocks become unsynchronized.

A better configuration would be to configure your internal server with 
four external servers.  The internal server will select the best of the 
four to synchronize with and the other three will act as an advisory 
committee and sanity check.  Any one of the four can have incorrect time 
or shut down completely and your internal server will still select the 
best remaining server.

This configuration leaves your internal server as a single point of 
failure.  A still better configuration would be to have four internal 
servers, each with four external servers, etc, etc.  How far you want to 
take this  depends on your needs for reliability, accuracy, and 
traceability of your timestamps. Your available resources can also be a 
factor.  Some applications do not have very demanding requirements; 
others can be very exacting.

So start be defining your requirements.  Then design a system that meets 

More information about the questions mailing list