Overriding CNAME and OTHER rule

Mark Andrews Mark_Andrews at isc.org
Mon Aug 27 05:39:36 UTC 2007

> Hello all,
> I am trying to use DNS to point one of my user's domains to their
> blogspot domain.
> Blogger gives directions here:
> http://help.blogger.com/bin/answer.py?answer=58317&query=CNAME&topic=&type=f#
> other
> The directions here say to have the target domain be a CNAME of
> ghs.google.com -- and I can understand why: If google renumbers their
> network, the zone files pointing at it are not at the mercy of that
> renumbering.  However, this comes with a restriction: I can point my
> user's SUBDOMAIN (such as www.theirdomain.com with a CNAME record),
> but I cannot successfully do this under BIND with the main domain
> (theirdomain.com) because at that point I will hit BIND'S "cname and
> other rule" that specifies I cannot have a CNAME record that refers to
> the same domain as the {SOA, NS, MX} records that are necessary to
> make the domain work.

	It is not BIND's rule.  It is a *requirement* of RFC 1034.
	RFC 1034, Section 3.6.2: "If a CNAME RR is present at a
	node, no other data should be present; this ensures that
	the data for a canonical name and its aliases cannot be
	different. This rule also insures that a cached CNAME can
	be used without checking with an authoritative server for
	other RR types."

> Is there a way to make this happen, or should I just do what I'm
> thinking of, get the IP for ghs.google.com, and create an A record
> with that IP?
> -Dan Mahoney
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: Mark_Andrews at isc.org

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