[Pdns-users] Secondary MX

Lorens Kockum lorens-pdns-3987 at tagged.lorens.org
Fri Mar 26 12:54:36 UTC 2004

On Fri, Mar 26, 2004 at 12:05:49PM +0000, MrDemeanour wrote:
> bert hubert wrote:
> >This story sounds like you setup a CNAME record instead of an A 
> >record.
> Negative, Captain.
> I did at one point try a CNAME, but that didn't work either; and anyway,
> I believe CNAME is deprecated for the purpose of aliasing hosts within a
> single domain.

Maybe the CNAME lived on in the cache while you thought you were
testing the A record. A record is the way to go.

For only defining IP addresses once, I like setting
www.example.com to be a CNAME to example.com, and define the A
for example.com.


I very much dislike CNAME for anything else, it has side effects
you can discover painfully. Like the fact that alias *means*
alias for *everything*. Including things that aren't in the
DNS. So if www.example.com is a CNAME for example.com, OK
the IP addresses are the same, OK the MX are the same, but
RFC-compliant MTAs will happily *rewrite*

	RCPT TO:<hello at www.example.com>


	RCPT TO:<hello at example.com>

For www to parent it's OK, but you can imagine the many ways to
disaster if you push it any farther.

This means that AFAIK (please prove me wrong) there is no way to
configure your DNS so that you can change the IP address of a
NameVirtualHost web server without individually modifying each
zone, the way you can with e-mail and MX. I ascribe this to the
fact that the www didn't exist when they invented DNS :-)


Of course, when the zones are on my server I simply SQL update

#include <std_disclaim.h>                          Lorens Kockum

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