FW: DNS Question

krad kraduk at googlemail.com
Fri Oct 23 14:56:42 UTC 2009

2009/10/23 Sean Cavanaugh <millenia2000 at hotmail.com>

> > 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    A
> www.vhost1.com          CNAME  www.bobshosting.com.
> www.vhost2.com          CNAME  www.bobshosting.com.
> www.vhost3.com          CNAME  www.bobshosting.com.
> www.vhost4.com          CNAME  www.bobshosting.com.
> -Sean
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I try to use CNAMES as much as possible, for one very good reason. If say I
have web server with 1000 vhost on it. I have one A record for the server
and all the cnames point at that A record. Now i need to change the ip of
the server. I update the A record and add a reverse record and im done. IF I
had done it your way with all A records I would now have to go and edit
another 1000 records. Even worse if some of these domains are not under my
control I have to go and liaise with customers, or other third parties, and
it becomes a complete mess. The chances of me convincing them all and
coordinated it correctly are minimal 8(

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