SOA record fundementals

[Sam Pointer]

I have a quick question if anybody would be happy to oblige. Thanks in
advance for any help/responses.

As I understand it the Zone Data File for any given zone can only have one
SOA record; fair enough. I also understand that the 1st field of the SOA
record is the FQDN of the primary master nameserver for the given zone.;
again fair enough.

So, to build an example, lets assume my SOA record looks like this:

mydomain.com.		IN	SOA	ns1.mydomain.com.
root.mydomain.com. (..etc)

Now, if I were to set up another *master* dns server for this zone, would
the SOA record for *that* server look like:

mydomain.com.		IN	SOA	ns2.mydomain.com. root.mydomain.com.
(..etc)
					
						OR

mydomain.com.		IN	SOA	ns1.mydomain.com. root.mydomain.com.
(..etc)


To put this in some context I'll explain what I am trying to accomplish. We
have 2 leased lines from 2 different ISPs. All our boxes are multi-homed
internally. I wish to have one set of DNS servers dishing out "ISP A"
addresses and another set "ISP B" addresses. Why? I hear you ask. Well, the
general premise is that (by keeping cachining TTL values very low - the
boxes are all low-traffic) if we get a problem with in-bound connectivity
with either of the ISPs we can take off-line their respective DNS servers at
our end and stop advertising the addresses. This will force all DNS requests
to resolve to the "good" ISP addresses thereby minimising distruption. When
everything clears itself up we can bring the DNS servers back up and have
both lines active again for in-bound traffic.

In short I want 2 different DNS servers on 2 different IP ranges to serve
the same domain names.

Again, thanks.


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