how to specify multiple nameservers?

[Mark.Andrews at nominum.com]

> 
> 
> Suppose three nameservers, answering IP addresses ip1, ip2 and ip3
> are authoritative for the zone 'domain.tld.'  Then is there any effective
> difference between the following master files:
> 
> CASE 1
> --------
> $ORIGIN domain.tld.
> @   IN SOA ...
>     NS   ns1
>     NS   ns2
>     NS   ns3
> ns1  A   ip1
> ns2  A   ip2
> ns3  A   ip3
> 
> CASE 2
> -------
> $ORIGIN domain.tld.
> @   IN SOA ...
>     NS   ns
> ns  A   ip1
> ns  A   ip2
> ns  A   ip3
> 
> It is my understanding that the replies generated by the above two
> specifications would lead to indistinguishable results in the behavior of a
> remote recursing BIND.  That is, the remote BIND would construct
> exactly the same list of nameservers for domain.tld., and would query
> them and age them out in exactly the same way.  Is that correct?
> 
> Do other nameservers behave similarly?  Are there other considerations that
> indicate a preference for one case or the other?
> 
> Thanks
> John Salmon
> 
> 
	BIND will anti-alias nameserver so if you were to list ip1
	as "bogus" all the servers in the second configurations
	will be treated as bad.

	Various registries don't cope with multi-homed machines
	(multiple A records).

	You also make debugging harder as people tend to assume that
	one name implies one machine.  You may know that they are
	multiple machines but the poor SA that is debugging a problem
	with one of your zones for their customers won't.

	Unless you have a really pressing need to do 2, I don't recommend
	it.

	Mark
--
Mark Andrews, Nominum Inc.
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: Mark.Andrews at nominum.com