DNS Question
DAve
dave.list at pixelhammer.com
Fri Oct 23 15:12:34 UTC 2009
Sean Cavanaugh wrote:
> > Date: Fri, 23 Oct 2009 08:30:08 -0400
> > From: dave.list at pixelhammer.com
> > To: freebsd-questions at freebsd.org
> > 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
--
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