secondary DNS server is meaningful?

[Mark_Andrews at isc.org]

> 
> 
> >No.  All servers are used - roughly equally.
> Thanks for your answer.
> then 
> 1. what's happening if the secondary DNS is down or not exist?

	If it's down the clients will ask the master after timing out.
	
> 2. what's happening if the primary DNS information and secondary DNS 
> information is not like?

	You get indeterminate answer depending apon which server is
	queried.

> 3. what's happening if the primary DNS information is correct but secondary 
> DNS has no data?

	If the secondary has no data it is not a secondary.

> 4. anyone who knows the document or site about the role of the secondary 
> DNS server?

	The roll of the secondary is the same as the master to the rest
	of the world.  Only the servers themselves need to worry about
	which is which (UPDATES should be directed to the master if it
	can be determined based on SOA MNAME but will be forwarded if
	it cannot be determined).  

> 5. I have lots of domains at one DNS server(secondary DNS is stopped), but 
> I didn't have some problems up to now, what's the meaning?

	The DNS is designed to cope with failures.  However you are wasting
	everyone elses resources by not having it running.

> So thanks in advance.
> 
> > > Hello all.
> > >
> > > I would like to know the rule of the secondary DNS.
> > > secondary DNS is just backup?
> >
> >No.  All servers are used - roughly equally.
> >
> > > so it is useless to operate secondary DNS if primary DNS is operated 
> well?
> > > But some case, a domain is not resolved properly when setup at just
> >primary
> > > DNS server.
> > > So I guess that the primary and secondary is important alike, right?
> > > I woule like to know the real role of the secondary DNS.
> > > just backup or not?
> > >
> > > Thanks in advance.
> > >
> > >
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--
Mark Andrews, Internet Software Consortium
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: Mark.Andrews at isc.org