which is the vaild a format?

Nick Hilliard nick-list at netability.ie
Mon Dec 11 09:41:22 UTC 2006

Farkas Levente wrote:
> ok actually the real problem is when web server is not in the given zone
> (but i just like to point to the problem in my original mail) like in
> this case:
> $ORIGIN example.com.
>                CNAME          www
> www            CNAME          virtual.webserver.com.
> in this case both record should have to be CNAME and the only place
> where any changes would have to made is in webserver.com zone.

If you want an IP address associated with the domain name, you need to 
insert the A record for virtual.webserver.com into the example.com domain. 
  You cannot do this with a CNAME because a CNAME is an alias record, and 
you can't have a record which has both real data and a record saying that 
the real data is actually another FQDN.

So you are stuck with:

$ORIGIN example.com.
www            CNAME          virtual.webserver.com.

There are several ways to deal with this issue in a production environment. 
  You could store all your DB records in a database and have some 
intelligence which deals with changing IP addresses for any relevant 
domains.  Or you could use some macro language like M4 which auto-generates 
zone files from a template.  Or you could simply use perl or sed in-place.

Of course, this becomes much more difficult when then domain is hosted by a 
third party, because you then have to instruct them to change all relevant 
IP addresses.


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