Sean Cavanaugh wrote:
> Date: Fri, 23 Oct 2009 08:30:08 -0400
> From: [email protected]
> To: [email protected]
> Subject: DNS Question
>
> Good morning.
>
> I have been asked by my co-workers and sales why I always create a A
> record for new domains we host instead of a CNAME.
>
> The issue I run into lately with some domains is that a client has a
> website with a industry host such as frank.relator.com and he wants to
> have DNS point www.frank.com to frank.relator.com with a CNAME. The
> client does not want an A record for frank.com.
>
> Somewhere, in a class far far away, I was taught a DNS zone had to have
> a A record to function properly. I can't seem to locate anything in the
> RFCs.
>
> Am I wrong?
>
I think you are confusing basics of DNS records. you are partially
correct in that a DNS zone needs an initial A record to be able to
translate a name to an IP, but there is nothing wrong about setting up a
CNAME to point to a record in a different zone instead. you just cannot
do a zone that has a CNAME only that does not at some point to a valid A
record. CNAMEs are forwarders only whereas A records are actual lookups.
for proper way to set this up....
The A record would be assigned for the main name that you want to
associate to an IP address.
The CNAME record just relates a different name to that original name.
this allows you to change the IP address of the server and only have to
update the original A record instead of every DNS record for that server.
for small number of vhosts, this would not really be an issue, but
imagine if you were hosting a couple hundred vhosts from a single IP and
then had to change that IP because you switched your ISP. It would take
you a LONG time to update them if they were all A records, but only a
couple of seconds if you had it properly set up as CNAME's
www.bobshosting.com <http://www.bobshosting.com> A 192.168.0.1
www.vhost1.com <http://www.vhost1.com> CNAME
www.bobshosting.com <http://www.bobshosting.com>.
www.vhost2.com <http://www.vhost2.com> CNAME
www.bobshosting.com <http://www.bobshosting.com>.
www.vhost3.com <http://www.vhost3.com> CNAME
www.bobshosting.com <http://www.bobshosting.com>.
www.vhost4.com <http://www.vhost4.com> CNAME
www.bobshosting.com <http://www.bobshosting.com>.
-Sean
All true, and I did not do a very good job of explaining it. My issue
was that we have requests to use a CNAME for the domain record. Such as
this.
example.com CNAME otherdomain.com
www.example.com CNAME otherdomain.com
I was taught this was not good form, but allowed. I can deal with it.
But what of having a SOA record for example.com, no A or CNAME record
for the TLD example.com, only hosts such as www, ns1, ftp, etc.
I tried it an it seems to work fine, but doesn't look proper to me. Then
again I remember when CNAME were considered evil.
DAve
--
"Posterity, you will know how much it cost the present generation to
preserve your freedom. I hope you will make good use of it. If you
do not, I shall repent in heaven that ever I took half the pains to
preserve it." John Quincy Adams
http://appleseedinfo.org
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