CNAME problem

[Mark_Andrews at isc.org]

> 
> I have a client for whom I just provide DNS service for his domain (say 
> 10001.org). He wants both 10001.org and www.10001.org to be aliased to 
> somewhere else (10001.ms.thirdcoast.net for both) using CNAME records.
> 
> My bind 8 running on Linux complains when I do try setting it up like this:
> 
> 10001.org.	IN	SOA	grad.applicom.com. adm.applicom.com. (
> 			2810545186
> 			36000
> 			3600
> 			360000
> 			3600 )
> 		IN	NS	grad.applicom.com.
> 		IN	NS 	kashmir.fdt.net.
> 		IN	MX	10 209.110.38.105.
> 		IN	MX	30 mailqueue.NETCOMI.COM.
> 
> 10001.org.	IN	CNAME	10001.ms.thirdcoast.net.
> www.10001.org.	IN	CNAME	10001.ms.thirdcoast.net.
> 
> 
> However the following works fine.
> 
> 10001.org.	IN	SOA	grad.applicom.com. adm.applicom.com. (
> 			2810545186
> 			36000
> 			3600
> 			360000
> 			3600 )
> 		IN	NS	grad.applicom.com.
> 		IN	NS 	kashmir.fdt.net.
> 		IN	MX	10 209.110.38.105.
> 		IN	MX	30 mailqueue.NETCOMI.COM.
> 		IN	A	129.41.60.55
> 
> www.10001.org.	IN	CNAME	10001.ms.thirdcoast.net.
> 
> Before I categorically tell my client that 10001.org could not be aliased, 
> please someone confirm or contradict and if you would, state your sources. 
> I studied ORA's "DNS and BIND" in detail but could not find reference that 
> would help with this. If it can be done, please tell me how.

	It's always been illegal.

RFC 1034:
"The domain system provides such a feature using the canonical name
(CNAME) RR.  A CNAME RR identifies its owner name as an alias, and
specifies the corresponding canonical name in the RDATA section of the
RR.  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."

	The SOA, NS and MX records constitute "other data".
	
	Note DNSSEC relaxed this to allow SIG and NXT records to co-exist
	with a CNAME record.

	Mark
--
Mark Andrews, Internet Software Consortium
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: Mark.Andrews at isc.org