RFC requirements for relative CNAME targets?

Charles Swiger cswiger at mac.com
Thu Jul 18 20:29:34 UTC 2013

On Jul 18, 2013, at 1:18 PM, John Miller <johnmill at brandeis.edu> wrote:
> I know that for the following record in example.com's zone file:
> host.example.com.  IN CNAME otherhost
> BIND will return:
> host.example.com. <TTL> IN CNAME otherhost.example.com.

Assuming $ORIGIN is set to example.com, but yes.

> Is this behavior required anywhere in the RFCs, or would
> 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.


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