Two More Questions on Hosting Three Domains on One Name Server

[Kevin Darcy]

Tom Naves wrote:

>I am going to host three domains on my dns servers:
>
>mydomain.com
>mydomain.net
>mydomain.de
>
>The NS Record for each domain is:
>
>        IN        NS        nameserver1.mydomain.com.
>        IN        NS        nameserver2.mydomain.com.
>
>Here are the SOAs for each domain:
>
>mydomain.com.        IN        SOA        nameserver1.mydomain.com. 
>dns.mydomain.com.   (
>
>mydomain.com.        IN        SOA        nameserver1.mydomain.com. 
>dns.mydomain.com.   (
>
>mydomain.com.        IN        SOA        nameserver1.mydomain.com. 
>dns.mydomain.com.   (
>
>In summary, I am using the same master and slave nameservers to host the 
>three domains.  I am using the same SOA and NS records for each of the three 
>domains.
>
>Is this correct?
>
Correct, with the nitpicky clarification that you're only referring to 
*some* of the fields of these SOA records' RDATAs. The serial numbers in 
these SOAs might vary if you make different numbers of changes to the 
domains, respectively.

>
>I have another problem with the reverse lookup zones.  All three domains are 
>on the same subnet and all three of the mail exchangers are on  two hosts:
>
>mail.mydomain.com is on          192.168.40.20
>mail2.mydomain.com is on        192.168.40.21
>mail.mydomain.net is on            192.168.40.21
>mail2.mydomain.net is on          192.168.40.20
>mail.mydomain.de is on             192.168.40.20
>mail2.mydomain.de is on           192.168.40.21
>
>It looks to me that I cannot have a reverse lookup for all mail exchangers. 
>So I will have reverse lookups for:
>
>20        IN        PTR        mail.mydomain.com
>21        IN        PTR        mail.mydomain.net
>
>and none for the other four mail exchangers.
>
>Should this be o.k.?
>
>Sorry for belaboring this, but I cannot find the information andywhere.  It 
>appears, sigh, to come with experience.
>
There is no requirement that the target of an MX record be in the same 
domain as the name of the MX record itself. So why even have separate 
names for mail[2].mydomain.{net,de}? Just define mail.mydomain.com and 
mail2.mydomain.com and point the MX'es of those other domains to those 2 
A records. That way you have a true forward/reverse consistency.

                                                                         
                                                         - Kevin