[ntp:questions] Re: should I make my servers peers to each other

Richard B. Gilbert rgilbert88 at comcast.net
Thu Oct 27 16:09:58 UTC 2005

Bob Kryger wrote:

>So here's the config. I have two systems that NTP sync to various
>servers on the internet. I have chosen both pool.ntp.org systems and one
>or two that I know are very close. I have tried to arrange it so that
>each server chooses a different server on the net as it's active server
>(without using preferred).
>I have some 40+ systems on the inside of my network that sync to these
>two boxes.
>Question: Should I, does it make sense to have my two servers peer to
>each other?
>(BTW, I'll prob have a few other questions while setting up the inside
>systems. It's been a fun and interesting project)
I don't think it will hurt to peer your two servers.   It is, however, a 
rather awkward configuration from the point of view of the clients.   
Configuring a client with two servers is the worst possible 
configuration; when the two servers disagree, as they almost inevitably 
will, the client has no basis on which to make a choice.   With a single 
server there is no choice; the client follows the server whether it's 
right or wrong.  With three servers in reasonable agreement the client 
can pick the one in the middle.   The problem with three servers is that 
if one fails altogether or is wildly wrong  you are back to the case of 
two servers.   Four servers are generally regarded as the minimum 
configuration to provide some robustness; four can unambiguously vote 
out one  false ticker.  The foregoing is somewhat over simplified but 
basically correct.

If you use a third server, with each of the three having at least one 
unique time source and peer the three you have a better configuration.   
It may be overkill for your needs; that's for you to decide.

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