Classless IN-ADDR.ARPA delegation.

[Barry Margolin]

In article <Pine.BSO.4.21.0002101806480.17687-100000 at NOC.maKintosh.com>,
John Kerbawy  <john at NOC.maKintosh.com> wrote:
>Hello. I'm trying to split up the delegation for a Class C like this:
>
>xxx.xxx.xxx.000.-229
>xxx.xxx.xxx.230.-235
>xxx.xxx.xxx.236.-247
>xxx.xxx.xxx.248.-255
>
>Is this possible? If so, what would the $ORIGIN be on the server end? Am I
>going to need to subnet this /24 into a /25, a /26, a /27, a /28, and 2
>/29s before I do the DNS side?
>
>I know I'm confused about something, I'm just not exactly sure what
>about. If you can tell, help me out. :)

Although RFC 2317 describes classless delegation in terms of CIDR blocks,
it's not really dependent on using real CIDR prefixes.  It can be used with
any subsets of a /24 block.  In your case, I would suggest delegating the
following zones:

0-229.xxx.xxx.xxx.in-addr.arpa
230-235.xxx.xxx.xxx.in-addr.arpa
236-247.xxx.xxx.xxx.in-addr.arpa
248-255.xxx.xxx.xxx.in-addr.arpa

In other words, instead of naming the subdomain after the CIDR prefix, name
it after the range of addresses it contains.

If the 0-229 block is managed by the same group that the class C itself is
delegated to, don't bother with the subdomain for that block.  Just put
those PTR records in xxx.xxx.xxx.in-addr.arpa zone.  This will save you
from having lots of unnecessary CNAME records.

-- 
Barry Margolin, barmar at bbnplanet.com
GTE Internetworking, Powered by BBN, Burlington, MA
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