SUMMARY: DNS - 1 server as primary for 2 domains and CNAMES

From: Larry Chin (
Date: Wed Mar 02 1994 - 04:15:31 CST

This summary encompasses two questions about DNS. The questions had to
do with:

A) One machine serving as primary for tow different domains
B) Maintaining the names of machine@domain after the machines have been
   moved to machine@sub.domain.

============================ Original Query #1 ===============================

Is anyone running DNS such that a single name server is the primary for
more than one domain ?

If so could you tell me how you set that up ?

Does the named.boot file simply have something like:

        primary domain-1 named.hosts
        primary domain-2 named.hosts

and then you put all the different machines into named.hosts as fully
qualified domain names ?

What about pointer records are they necessary ?

I am faced with having to be the primary for the and
domain and I am not too sure how to go about doing on a single machine.
I would rather not have more than one primary machine, for various


As it turns out the only thing that is really required here is separate
zone and zone rev files for each domain as well as the appropriate
entries in the named.boot file.

IMHO the easiest way to accomplish this dual domain with one primary
scenario is to formulate a set of DNS files for each domain and then
just combine the entries from the boot files into a single file.

For example:

In my case I am dealing with and so the boot file
would appear as.

        primary named.hosts

        primary rev.netxxx
        primary rev.netyyy

Now comes the tricky part.

While the above is a simple solution, my particular situation was
complicated by the fact that the machines in all had to be
moved to BUT certain machines had to be maintained, at least
as aliases, within the original domain.

So, I had not only to maintain a single machine as primary for two
domains but also to maintain the same machines with different names in
both domains. This led to posting #2.

============================ Original Query #2 ===============================

I have just recently changed our domain name from
to That all was fine, however I need to maintain
aliases for a couple of the machines such that their names
use the old domain name.

For example:

What used to be:

is now:

But I need to maintain an alias for machine such that the
machine will still be known as:


I have been told that in the CA.CCH.COM zone file I cannot
have something like:

But putting something like:

         machine IN A CNAME

is illegal.


As it happens, matters were being confused by the fact that one machine
was acting as primary for both and As a result, the
information in the zone files would interact to make it appear that
illegal data was present in the files.

The solution to the problem was provided by dave barr
( ). Basically all that is needed is CNAME records in
the domain that point at the subdomain thusly. in cname in cname

This would in effect cause a lookup for to be halfway
resolved to the name of the machine in the subdomain.
A query would be sent to the domain server for the
subdomain for final resolution.

For mail delivery to be effected to the subdomain machines that are
listed as CNAME records in the parent domain, an entry as below would
also be needed.

- In the parent's zone file in mx

- In the subdomain's zone file. in a in mx mailhost in a in mx mailhost

Many thanks to those who responed:

Todd Kover <kovert@cs.UMD.EDU> (John Justin Hough) (Fabrice Guerini) (Cecil Pang)
Piete Brooks <>
jason andrade <>
Dallas N Antley <>
Richard Butler <>
Claude Marinier <> (Steve_Kilbane) (Mike Hill)
fabrice@cisk.ATMOS.Ucla.EDU (Fabrice Cuq) (Robert Wolf) (John Justin Hough) (Bruce Gourd)
Jaap Bril <>
David Barr <>
stuart@TO.Mobil.COM (Stuart Pearlman - RDR)

Wed Mar 2 05:11:51 EST 1994
Larry Chin {} CCH Canadian Ltd.
System Administrator 6 Garamond Court
Research and Development North York, Ontario.
(416) 441-4001 ext. 349 M3C 1Z5

Death is nature's way of telling you to slow down

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