Virtual Hosts don't work with "www"

Kevin Darcy kcd at
Wed Feb 21 02:32:49 UTC 2007

Stephane Bortzmeyer wrote:
> On Mon, Feb 19, 2007 at 08:29:28PM -0500,
>  Kevin Darcy <kcd at> wrote 
>  a message of 26 lines which said:
>> Using CNAME means you have one less A record to update if you
>> re-address your server. It also means there is zero ambiguity with
>> respect to forward/reverse record consistency. So from a
>> manageability perspective, CNAME is preferred.
> Surely, nobody still edits zone files by hand, except for small and
> unimportant domains? Zone files are typically generated by a program
> like h2n or pre-processed through m4 / cpp / whatever so there is
> really no diference "from a manageability perspective".
There is more to DNS manageability than just the mechanism by which data 
gets from the administrator's fingers to the actual physical zone file. 
That's just the lowest level of abstraction, but manageability also 
applies to the higher layers, which tend to be more database-oriented 
(and are often in fact real databases). If the maintenance subsystem, as 
a whole, is oriented towards *addresses* being the "primary key" of the 
database, which is typical when the DNS maintenance subsystem is tightly 
integrated with an IPAM (IP Address Management) subsystem, then it can 
be problematic to have multiple names pointing to the same address, 
because that requires all sorts of exceptions and special cases. It 
creates a many-to-one relationship where naturally a one-to-one 
relationship should suffice. CNAMEs provide a convenient way to have 
multiple DNS names resolve, albeit indirectly, to the same IP, without 
having to introduce troublesome multiple references and/or many-to-one 
relationships within the A-record database itself.

- Kevin

P.S. For the record, we use a homegrown DDNS-based subsystem here for 
DNS maintenance, and are transitioning to a commercial DNS/DHCP/IPAM 
product. We haven't used hand-editing of zone files as our primary 
method of DNS maintenance for many many years. As for h2n/m4/cpp-based 
approaches, we skipped that evolutionary step altogether.

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