several master ip's for a slave zone

Barry Margolin barmar at
Mon Nov 7 03:54:40 UTC 2011

In article <mailman.1.1320621651.68562.bind-users at>,
 Chris Thompson <cet1 at> wrote:

> On Nov 5 2011, Alan Clegg wrote:
> >On 11/5/2011 4:21 AM, kalpesh varyani wrote:
> >> How does this feature address the risk that data provided by one master
> >> might get overwritten by another?
> >
> >The use of the word "masters" in the configuration of a slave zone is a
> >bit misleading.  Under most circumstances, you list the authoritative
> >servers, not "multiple masters".
> Although Alan doesn't say so, this might suggest to some that you should
> list *all* the authoritative servers. That's a very bad idea - you need
> to arrange that the directed graph of "A can fetch from B" is acyclic.
> Otherwise servers can get into the state that A thinks its copy of the
> zone is up to date because B told it so, and B thinks so because A told
> it so (or longer loops, of course), while neither of them are true masters
> for it.

I don't think it's a problem.  As long as ANY of the servers in the 
masters list have a higher serial number, you'll fetch from it.

So if you have three servers, A, B, and C, A will check the serial 
numbers on both B and C, and pull from whichever has a higher serial 
number than the serial A already has.

Barry Margolin
Arlington, MA

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