RFC requirements for relative CNAME targets?

John Miller johnmill at brandeis.edu
Thu Jul 18 23:47:21 UTC 2013

On 07/18/2013 06:07 PM, Barry Margolin wrote:
> In article <mailman.844.1374184195.20661.bind-users at lists.isc.org>,
>   John Miller <johnmill at brandeis.edu> wrote:
>> 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.
> All names in a zone file that do not end with "." get the $ORIGIN
> appended to them. This is required by the zone file specification.

Thanks to everyone for their help with this.  You also spurred me to dig 
into RFC 1034/1035 a bit more deeply than I'd done in the past.  Not as 
painful as I'd feared.

 From RFC 1035, Section 5.1:
"Domain names which do not end in a dot are called relative; the actual 
domain name is the concatenation of the relative part with an origin 
specified in a $ORIGIN, $INCLUDE, or as an argument to the master file 
loading routine.  A relative name is an error when no origin is available."

In other words, for any record type that contains a domain name in its 
RDATA section (CNAME, NS, SOA, MX, SRV, etc.), the nameserver must make 
sure that the domain name is either fully qualified, or it must append 
an origin somehow.


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