Ambiguous def of multiple CNAME

[Barry Margolin]

In article <525414697.943979944011.JavaMail.qtran at hutch.East.Sun.COM>,
 <Christine.Tran at east.sun.com> wrote:
>The bind config file guide -- options statement says:
>
>multiple-cnames
>	If yes, then multiple CNAME resource records will be allowed for a
>	domain name.  The default is no. <snip>
>
>Which is forbidden, this(1):
>
>oak	IN	CNAME	tree.foo.com.
>birch	IN	CNAME	tree.foo.com.
>
>or this(2):
>
>oak	IN	CNAME	tree1.foo.com.
>oak	IN	CNAME	tree2.foo.com.
>
>or this(3):
>
>tree	IN	A	1.2.3.4
>tree	IN	A	5.6.7.8
>oak	IN	CNAME	tree.foo.com.
>
>(2) and (3) tries to achieve the same effect.

(2) is normally forbidden, and multiple-cnames will allow it.
"oak.<origin>" is the domain name that the documentation is referring to.

>Say I am auth for foo.com and not auth for blat.com.  Can I do:
>
>server.foo.com.	IN	CNAME	server.blat.com.
>I am almost sure it's not kosher, but so far it's worked.  I'm on BIND8.2p1.

Why wouldn't this be kosher, since it's what CNAMEs were originally created
for?  They were created to ease the conversion from the old flat namespace
(all the old Arpanet hostnames simply became <hostname>.ARPA) to the new
namespace under multiple TLDs; e.g. MIT-MC.ARPA might have been a CNAME for
MC.LCS.MIT.EDU.

And nowadays it would be common for a customer of a web hosting provider to
have something like:

www.customer.com.  IN CNAME  server-133.provider.net.

-- 
Barry Margolin, barmar at bbnplanet.com
GTE Internetworking, Powered by BBN, Burlington, MA
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