Re: different domains in the same subnet ?

[Jim Langston <jimlangston@xxxxxxxxxxxxxxxx>]

Yes.  Though probably not the way you expect.  You can do what you
want to do, have 2 different e-mail domains from the same network.
This is not a problem, I will explain how.  Problems can crop up though.

A DNS server will have an entry for each domain.  Say you are someone.com
A DNS server will have a few lines (can't remember if it's MX or A) such as

What will happen is anyone who looks for the IP of someone.com will get 
directed to the machine 11.22.33.44.  If they go to mail.someone.com they
will also go to the same machine, 11.22.33.44.  Now, you want a new domain
name.  So you pick something like something.com.  You just add some more
MX records...

      MX   someone.com         11.22.33.44
      MX   mail.someone.com    11.22.33.44
      MX   joe.someone.com     11.22.33.45
      MX   something.com       11.22.33.44
      MX   mail.something.com  11.22.33.44
      MX   joe.something.com   11.22.33.45

As you can see now, you can get to the machine 11.22.33.44 by using 4 different
names, someone.com, mail.someone.com, something.com or mail.something.com.  All
are the same machine.  All a DNS server does is resolve the machine IP name to 
an IP address.  Multiple entries are fine.

There is another record called an A record.  It looks something like

       A    11.22.33.44  someone.com

There can only be one A record for each (again, I may have MX and A's reversed).
What this A record does, if I do a lookup on an IP address, such as 11.22.33.44 
the
A record will return that machine name.  In this case someone.com.  Even though 
there
are really 4 names for this machine, I only see one of them on a "reverse DNS 
lookup"
such as ping -a 11.22.33.44.

Now you want to "route emails to them".  You really do not route an e-mail to a 
user's
machine, you route e-mail to a mail server.  Then the user's machine uses a 
client
(such as netscape, Outlook, Lotus Notes, etc...) to go to the server and 
retrieve the
e-mail.

Very easy to set up 2 e-mail servers with two different domain names (even 
possibly on
the same server, even possibly in the same mail server program!  depends on 
what you
are using for e-mail serving).  In the given case, e-mail I send to 
you@someone.com 
will go to the same machine as you@something.com

It would be much easier to set up a separate mail server for the second domain 
name
though.

Sorry if I've totally confused you.

Regards,

Jim Langston

Date: Fri, 13 Oct 2000 12:08:39 -0400
From: "Valentin Petrov" <vpetrov@acme400.ACMESTEEL.COM>
Subject: different domains in the same subnet ?

Can I put different domain names in the same subnet with different IP 
addresses? I want to rout emails to them.
I could not find any restrictions about that, but I prefer to ask the 
'knowledge base' first.
Thanks for your help !

Valentin
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