Why two lookups for a CNAME?

Karl Auer kauer at biplane.com.au
Wed Oct 21 21:37:37 UTC 2015


On Wed, 2015-10-21 at 20:42 +0000, Lightner, Jeff wrote:
> Because the purpose of DNS primarily is to equate a name with an IP as
> applications talk to IPs not to names.   When you have a CNAME you’re
> equating one name with another name.   That other name then has to be
> looked up so the application knows what IP access.

This doesn't answer the OPs question (which is a good one). He's saying
that the required IP address has *already been returned* in the first
response, so why is a second query made?

When I use dig to do a lookup of a cname, it makes only one query:

; <<>> DiG 9.9.5-3ubuntu0.5-Ubuntu <<>> www.angihigh.com.au
[...]
;; ANSWER SECTION:
www.angihigh.com.au/ ... CNAME   angihigh.com.au.
angihigh.com.au.     ... A       27.121.64.62
[...]

Maybe the application mentioned by the OP is not a smart as dig.

Regards, K.


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