Virtual DNS questiona and reverse lookup table conflicts

[Veli-Pekka Kestilä]

Daniel B. Thurman wrote:
> Christopher K. Johnson wrote:
>> Bruno Wolff III wrote:
>>> On Sat, Dec 06, 2008 at 13:34:06 -0800,
>>>   "Daniel B. Thurman" <dant at cdkkt.com> wrote:
>>>  
>>>> Is it possible to have a single DNS server support
>>>> two different domain names, with each domain
>>>> name having it's own forward and reverse lookups?
>>>>     
>>>
>>> It is possible for PTR lookups to return different results based on the
>>> IP address that the request comes from. I don't use bind and so can't
>>> give you advice on how to set this up (assuming that it will solve your
>>> problem), but googling for "split horizon" and "bind" should find help
>>> in doing that.
>>>   
>> Check out "bind views".
>>
> Thanks for the tips.
>
> But the more I think about it, how does bind know which
> reverse ip domain name to return?  Domain1 or Domain2?
>
> I am missing the logic behind this.
>
> It matter which domain name is returned because nowadays, there
> are email sites that do a reverse ip lookup to ensure that the domain
> name matches with the ip address and if they don't match - the email
> message is rejected, for example.
>
As far as I know you can have only one reverse map for one ip-address. 
But for the e-mail server it should be enough for you to have one valid 
forvard reverse pair.

If you have two domains domain1 and domain2 you would just make the 
domain2 use mail.domain1 as it's mail server. If mail server checks if 
the mail server is in same domain with mail address it's too braindead 
to be used as there is too many domains which use mail servers belonging 
to other domain.

So in domain1.com bind config you would have

         IN MX 1 mail.domain1.com.
mail   IN A 10.0.0.1

In reverse you will have

1 IN PTR mail.domain1.com.

And in domain2.com forward you would put.

IN MX 1 mail.domain1.com.

-VPK