RFC requirements for relative CNAME targets?

Novosielski, Ryan novosirj at ca.rutgers.edu
Thu Jul 18 21:59:00 UTC 2013

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.


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.

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