CNAME or A record?

[Joseph S D Yao]

On Wed, Sep 28, 2011 at 04:19:41PM +0200, feralert wrote:
...
> The thing is that i want users redirected to 'www.domain.com' even
> when they just type the domain name 'domain.com'.
> In order to do so I am not sure if its best to have one A RR for each
> or have an A RR for the domain and a CNAME RR pointing to 'domain.com'
> for 'www.domain.com'.
> 
> 
> domain.com           A            1.1.1.1
> www.domain.com   A            1.1.1.1
> 
> OR
> 
> domain.com           A            1.1.1.1
> www.domain.com   CNAME  domain.com
...


It's clear you need an entry for both.  Which is a matter of future
maintenance.  If you only want to change it in one place, and you'll
never need any other records for "www" different from those for the
domain itself, go ahead and use the CNAME.  (Multiply this by 1000 times
in 1000 different domains, or maybe all within the one domain, and it
may matter.  OTOH, if you are using one file for 1000 different domains,
you CAN't use the CNAME.  I don't think.)

The only downside, besides not being able to have other records for the
"www" name, is that the resolver now has to make TWO queries.  If your
name server is a PDP-11/05 running Unix V6 and BIND 4.1.2, this might
make a difference.  [And if so - may I see it?  ;~)]  However, most name
servers these days are made of sterner stuff.  And if you're truly doing
a "redirect" instead of just serving the same Web site at both names,
it'll have to make two queries anyway.

As someone tried to say but didn't [too many pronouns, not enough clear
antecedents], a "redirect" would be done by your Web server, not by DNS.
The Web server at "domain.com" would say, go away, nothing to see here,
it's all going down at "www.domain.com".  And the Web server at
"www.domain.com" would have all the goodies.  But if you're serving the
same Web content at both names, that's NOT a "redirect".  Whichever you
do, as I started out saying, you need both DNS entries.  Whatever they
may be.


--
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** Joe Yao				jsdy at tux.org - Joseph S. D. Yao
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