Multiple PTR or not?

[Will Yardley]

In article <aitqlk$f67c$1 at isrv4.isc.org>, jeff donovan wrote:

>>Could you just setup the required machines to search the k12.pa.us
>>domain? If you are using Unix or Windows, this is pretty straight

> the k12.pa.us domain is currently setup and running ( has been for
> years ). and I have been asked to add bethsd.org in addition to the
> k12 domain. It's not like I'm just adding a web server. They want to
> have both domain names function for the same address space ( which is
> several class C blocks ).  Where i get confused is that this is not a
> sub domain that is under the .us tree.
> 
> My problem is understanding how reverse lookups should be handled. i
> can create the the forward files with the same addresses as the k12
> domain, but then what do I do about reverse lookups. At this point I
> have been advised several times "not" to use multiple PTR records.
> 
> to me this doesn't seem logical. two domains using the same address
> space. The primary dns server will actually function as
> dns.beth.k12.pa.us and ns.bethsd.org.

It really depends... for stuff like nameservers, mail servers, websites
with secure certificates it's a good idea to use unique IPs for each,
and to have the correct PTR for each record... however for other stuff
(websites, etc.) it's not necessary.

We have virtual domains with at least 50-100 unique domains and
subdomains associated with it - each only has one reverse entry (which
is usually unrelated to any of the forward domains)...

If you have several class C blocks, you should have more than enough
addresses to assign unique IP addresses (with proper reverse mapping)
for the machines and / or services that need them.

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