aliases in DNS, and excluding a name to be looked up from external DNS

Gregory Hicks ghicks at cadence.com
Tue Jul 11 16:55:03 UTC 2006


> From: sasan3 at gmail.com
> Date: 11 Jul 2006 01:49:29 -0700
> 
> Let's say I have a computer comp.mydomain.com in my local DNS. How do I
> add an alias in the DNS files basically saying "comp" is the same as
> "comp.mydomain.com"? I know I can put this in the /etc/hosts, but I
> just can't get this to work with A and CNAME records!!! :(

First off, you really don't want to go down this path.  Use FQDN
names.  ALWAYS!

Having said that, the trick is to set up your /etc/resolv.conf on each
client properly.

domain mydomain.com
search mydomain.com someotherdomain.com
nameserver x.x.x.x
nameserver x.x.x.x

A cavaet:  Whatever directive (domain/search) is SECOND in
/etc/resolv.conf is the one that is controlling.  The SECOND directive
takes precedence over the first.  (The "domain" directive is not really
needed here but is included for completeness.)

> Also, I want all names within xxxx.mydomain.com to be resolved by local
> DNS. But I want www.mydomain.com to be resolved by external DNS. How
> can I add this exception to my DNS table?

Point your internal machines at your local nameserver via your
/etc/resolv.conf.  Let the root delegation for mydomain.com handle
external clients.  This means that you have two sets of nameservers to
maintain.

Of course, your internal nameservers will have to be authoritative for
mydomain.com (stealth masters) and may, or may not, have any relation
to the external servers.

You're going to run into a bit of a problem here if you want only one
host in your domain to be resolved by the external nameservers.  To
wit, either the local nameservers are authoritative or they are not.
If they ARE authoritative but do not define www.mydomain.com, then as
far as the internal clients are concerned, that host does not exist.
Because the internal servers are authoritative, those DNS requests will
not be forwarded.

Sorry, but that's the way the system works.

Regards,
Gregory Hicks

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