Classless Reverse zones

Bob Vance bobvance at
Thu Mar 15 20:39:28 UTC 2001

>Normally it's 4 consecutive, bit aligned, NS RRsets.

What in the heck does that mean?  :)

>It really shouldn't be used for /0-/24.

Why is that?
I was thinking that it would be used anytime you want to delegate on
*non-octet* boundaries, not just sub "Class C".  The reverse lookup is
based on the octets, so if there is a split in authority in *any* of the
octets, then CNAMEs could be used to point to the correct zones.
Am I wrong?

Tks        | <mailto:BVance at>
BV         | <mailto:BobVance at>
Sr. Technical Consultant,  SBM, A Gates/Arrow Co.
Vox 770-623-3430           11455 Lakefield Dr.
Fax 770-623-3429           Duluth, GA 30097-1511

-----Original Message-----
From: bind-users-bounce at [mailto:bind-users-bounce at]On
Behalf Of Mark.Andrews at
Sent: Wednesday, March 14, 2001 9:27 PM
To: "Peter Anderson"
Cc: comp-protocols-dns-bind at
Subject: Re: Classless Reverse zones

	Classless IN-ADDR using CNAMES is for cases where you can't
	use classic delegation techniques and don't what to delegate
	each individual reverse address.  It really shouldn't be
	used for /0-/24.
> Has anyone created a zone with a 22 bit (or less) mask and $GENERATE?

	Yes. You use 4 $GENERATE statements.

> I can't seem to get it to work and all the other examples I've found
are for
> subsetting a class C subnet.

	That's what it was designed for.

> For example with a 22 bit mask do you have 4 NS recs in the parent

	Normally it's 4 consecutive, bit aligned, NS RRsets.

> This is all for internal DNS setup not connected with the internet at
> and we're getting lots of these subnets being used for dynamic
updates, and
> I'm trying to work out a way of reducing the number of zones.

	I think you have enough information to do that if you still
	want to.

> Thanks,
> Peter Anderson
> Senior Communications Analyst
> <Remove ETER from my address to reply>
> Any views or opinions presented are solely those of the author and do
> necessarily represent those of Westpac Banking Corporation.
> --
> Posted from []
> via Mailgate.ORG Server - http://www.Mailgate.ORG
Mark Andrews, Nominum Inc.
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET:
Mark.Andrews at

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