DNS hostnames with a duplicate CNAME and A record - which should be removed?

Tony Finch dot at dotat.at
Thu Oct 18 08:56:56 UTC 2012


Landon Stewart <lstewart at superb.net> wrote:
>
> The problem is that we have some zones that have records with the same
> hostname that have both a CNAME as well as an A record, MX record, SOA
> record and/or NS record.  Is there an easy answer for what should be
> removed?

You can never have a CNAME record at a zone apex, because a zone apex has
to have SOA and NS RRs and a CNAME can never coexist with other RRs. So
those cases are simple.

If the misconfigured CNAME is not at a zone apex then you have to decide
whether the CNAME or the other records are correct - do you get the right
result from the DNS when deleting one or the other? If it works either way
then your decision mainly depends on how frequently the target address
changes and if you need to make co-ordinated changes across many zones -
if so then a CNAME tends to be preferable. But you probably have to have a
workaround for A records at zone apexes in which case that tooling
probably removes CNAMEs' advantage and you might as well use A records
everywhere.

Tony.
-- 
f.anthony.n.finch  <dot at dotat.at>  http://dotat.at/
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