IN SOA format

Mark Andrews Mark_Andrews at isc.org
Fri Sep 19 01:53:35 UTC 2008


In message <barmar-4578A9.21280118092008 at newsgroups.comcast.net>, Barry Margoli
n writes:
> In article <gau0bf$3u7$1 at sf1.isc.org>,
>  Mark Andrews <Mark_Andrews at isc.org> wrote:
> 
> > In message <DAE2574A7F44F44ABE07381C36213DFA0592002B at exch.cdltd.co.uk>, "Pa
> ul 
> > Cocker" writes:
> > > If a computer has multiple names, say a regular hostname and a CNAME
> > > "ns" which points at the hostname and is used as the first nameserver
> > > for a domain, should the hostname or "ns" be used on the IN SOA line?
> > 
> > 	NS records cannot refer to CNAMES.  NS record have to refer
> > 	directly to A or AAAA records.
> 
> But his question was about SOA records, not NS records.

	I know, but what he is planning to do won't work.  It the
	DNS protocol does not support it.  The additional processing
	rules don't allow it work.

	The decribed configuration (below) will NEVER work as you
	can't delegate to a CNAME.  Remember glue is a copy of a
	address (A / AAAA) record.

		example.com. SOA ns.example.com. hostmaster.example.com. (
				 1 3600 1200 3600000 360000 )
		example.com. NS ns.example.com.
		ns.example.com. CNAME foo.example.com.
		foo.example.com. A 1.2.3.4

	To make it work NS needs to point to address records.

	e.g.
		example.com. SOA ns.example.com. hostmaster.example.com. (
				 1 3600 1200 3600000 360000 )
		example.com. NS ns.example.com.
		ns.example.com. A 1.2.3.4
		ns.example.com. AAAA 2001::1
		foo.example.com. A 1.2.3.4

	Having the "wrong" name in the SOA record will just result
	in a few extra NOTIFY messages or a machine which should
	get a notify not getting one.  The SOA timers will cover
	the later.

	Mark
 
> In most cases the hostname in the SOA record is not used, so it's not 
> important what it is.  The only common use of it is if dynamic DNS 
> updates are in use, it tells the clients where to send their updates.  I 
> expect that they will follow CNAMEs.
> 
> -- 
> Barry Margolin, barmar at alum.mit.edu
> Arlington, MA
> *** PLEASE don't copy me on replies, I'll read them in the group ***
> 
-- 
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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