CNAME for main domain

[Mark_Andrews at isc.org]

> 
> Am I correct in understanding that a PTR record can indicate a CNAME?

	PTR's (like every other record that refers to another **) should
	refer to the cannonical name.  

	What is on the RHS of a CNAME is the cannonical name.  The LHS
	is the alias.

		<alias> CNAME <cannonical-name>

	** CNAME chains are to be expected.

> For some reason I thought that this would interfere with certain
> programs (like MTAs and SSHD) that do reverse DNS calls: I thought
> that in trying to verify a hostname they would look it up, follow any
> CNAMEs, note the A record's name, and verify that the IP's reverse
> mapping matched the A record. Would they instead check that the IP
> matched either the A record or one of any CNAMEs? If a PTR at a CNAME
> is both without the complications I described and standards-legal,
> then it would indeed prevent the reverse-record untidiness I feared.

	I'll leave this alone as it is based on the incorrect assumptions.

> (It struck me as tacky and artificial to have an IP resolve to the
> zone apex.)

	Well example.com is just as much a hostname as www.example.com.

	The reason why people started using www.example.com was to move
	the service to a different machine to that which was handling
	example.com.

	Mark
> 
> - Greg
> 
> Danny Mayer <mayer at gis.net> wrote in message news:<as01iq$508c$1 at isrv4.isc.or
> g>...
> > At 05:46 PM 11/25/02, Kevin Darcy wrote:
> > >No, when a name owns a CNAME, it cannot legally any other record. The
> > >zone apex in your example owns an SOA and 2 NS records, so it cannot
> > >legally own a CNAME record.
> > >
> > >If you want the zone apex name to resolve to an address, you must use an
> > >A record for it rather than a CNAME. There's no problem making the
> > >"www" name an alias for the zone apex name, however, so that should fix
> > >your reverse-record "untidiness".
> > 
> > This really has nothing to do with the reverse-record. These are the forwar
> d
> > records. You can put whatever you want in the PTR records. In this case
> > you apparently want it to point back to the www name.
> > 
> > Danny
> > 
> > 
> > 
> > >- Kevin
> > >
> 
--
Mark Andrews, Internet Software Consortium
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: Mark.Andrews at isc.org