RFC requirements for relative CNAME targets?

John Miller johnmill at brandeis.edu
Thu Jul 18 23:11:00 UTC 2013

Hi Ryan,

Sorry I wasn't more clear in my original post.  Barry hit the nail on 
the head:  I was curious if the RFCs required BIND to append $ORIGIN to 
targets that aren't fully qualified.  Sounds like they do.

I appreciate the help!


On 07/18/2013 05:59 PM, Novosielski, Ryan wrote:
> Are you asking if the target of a CNAME need be an FQDN if $ORIGIN is
> defined? If so, no, I use short names (no trailing dot) all the time.
> *From*: John Miller [mailto:johnmill at brandeis.edu]
> *Sent*: Thursday, July 18, 2013 05:49 PM
> *To*: Bind Users Mailing List <bind-users at lists.isc.org>
> *Subject*: Re: RFC requirements for relative CNAME targets?
> On Thu, Jul 18, 2013 at 4:29 PM, Charles Swiger <cswiger at mac.com
> <mailto:cswiger at mac.com>> wrote:
>     On Jul 18, 2013, at 1:18 PM, John Miller <johnmill at brandeis.edu
>     <mailto:johnmill at brandeis.edu>> wrote:
>      > I know that for the following record in example.com
>     <http://example.com>'s zone file:
>      >
>      > host.example.com <http://host.example.com>.  IN CNAME otherhost
>      >
>      > BIND will return:
>      >
>      > host.example.com <http://host.example.com>. <TTL> IN CNAME
>     otherhost.example.com <http://otherhost.example.com>.
>     Assuming $ORIGIN is set to example.com <http://example.com>, but yes.
>      > Is this behavior required anywhere in the RFCs, or would
>      >
>      > host.example.com <http://host.example.com>. <TTL> IN CNAME otherhost.
>      >
>      > be equally valid from an RFC perspective?  Obviously this would
>     also pertain to NS, MX, SRV, PTR, etc. records.
>     "otherhost." is equally valid from an RFC perspective, or
>     "otherhost.other.domain."  If there is a trailing dot, the CNAME
>     target is assumed to be fully qualified, otherwise $ORIGIN is
>     appended just as it would be for any other record using an
>     unqualified name.
>     Regards,
>     --
>     -Chuck
> I think what I was getting at was whether appending $ORIGIN to an
> unqualified target--only talking target, not label--was _required_ by
> the RFCs, and if so, the RFC/section.  I'll read through 'em; was just
> hoping someone knew the answer off the top of their head.
> John

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