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From: huntting@csn.org
Newsgroups: comp.protocols.tcp-ip.domains
Subject: Re: PTR records of gateways on the Internet
Message-ID: <1991Jan13.231345.19844@csn.org>
Date: 13 Jan 91 23:13:45 GMT
References: <1991Jan9.195641.17628@slcs.slb.com>
Sender: huntting@csn.org (Brad Huntting)
Organization: Colorado SuperNet Inc.
Lines: 50

7thson@slcs.slb.com (Chris Garrigues) writes:

>    If a host or gateways has multiple addresses, these addresses SHOULD
>    have PTR records pointing either to the same name OR to names with CNAME
>    records pointing to a common name.

Wait a sec...  Are you advocating the following:

glarp.x.		in	a	128.1.1.1
glarp.x.		in	a	128.1.2.2

glarp-intf1.x.		in	cname	glarp.x.
glarp-intf2.x.		in	cname	glarp.x.

1.1.1.128.in-addr.arpa.	in	ptr	glarp-intf1.x.
2.2.1.128.in-addr.arpa.	in	ptr	glarp-intf2.x.

My understanding was that only canonical names should be referenced in
RR's.  In the above example, the names `glarp-intf[12].x' are not
canonical, and so should not be refered to in ptr records (or any other
records for that matter).  What should gethostbyaddr(128.1.1.1) return
in such a case?  `glarp-intf1.x' or `glarp.x'?  BIND4.8.2 will (I
believe) return `glarp-intf1.x'.

Is a nameserver supposed to do cname lookups only at the begining of a
queary and not bother after it has found data?  Is this written down
somewhere?

Consider a similar case:

foo.x.			in	mx 10	foo.x.
			in	mx 20	mhub.x.
mhub.x.			in	cname	glarp.x.

Someone at my site recently did this.  And hosed themselves pretty
good.  `Glarp' was supposed to spool mail `foo''s mail when `foo' was
down.  Insted it was trying to contact `mhub', and was getting confused
whilest "talking to itself".  All this basically because the resolver
was expecting a canonical name and got `mhub'.

The machines ruleset 0 was smart enough to deliver mail for `mhub'
locally.  I suppose we might have been able to solve this by forcing
the name `mhub' into the $=w macro in sendmail.cf.  Insted we just
changed the mx 20 record to point go `glarp' directly.

brad
	huntting@csn.org
	huntting@colorado.edu

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