Question about RFC-2317

Mark Andrews Mark_Andrews at isc.org
Thu Jan 4 12:15:37 UTC 2007


> I was reading about RFC-2317
> (http://www.ietf.org/rfc/rfc2317.txt, found via google... is
> there a newer one?) 
> 
> While I feel I have grasped a lot about DNS/Bind the past
> couple months (enough to setup zones for my LAN and started
> to manage a couple external domains I've since had deligated
> to me), I can't see understand one part in this RFC document.
> 
> On page 2 (and 3) it shwos a nice example of how to partition
> a class C address space into chunks (in that case, starting
> from 192.0.2.0, /25, /26, and /26
> 
> I understand that CNAMing in the parent zone is needed,
> acccording to this RFC.
> 
> What I can't seem to figure out for the life of me is *why*
> this is needed?

	To map from the well known name where the PTR is expected
	to be to the name in the other zone where the PTR record
	actually will be.

	Most of the DNS based RFC's require that you have read
	and understood the base documents for the DNS

		RFC 1033, RFC 1034 and RFC 1035.

	Mark

> (Example parent zone from RFC-2317)
> ---------------------------------------
>    $ORIGIN 2.0.192.in-addr.arpa.
>    @       IN      SOA     my-ns.my.domain.
> hostmaster.my.domain. (...)
>    ;...
>    ;  <<0-127>> /25
>    0/25            NS      ns.A.domain.
>    0/25            NS      some.other.name.server.
>    ;
>    1               CNAME   1.0/25.2.0.192.in-addr.arpa.
>    2               CNAME   2.0/25.2.0.192.in-addr.arpa.
>    3               CNAME   3.0/25.2.0.192.in-addr.arpa.
>    ;
>    ;  <<128-191>> /26
>    128/26          NS      ns.B.domain.
>    128/26          NS      some.other.name.server.too.
>    ;
>    129             CNAME   129.128/26.2.0.192.in-addr.arpa.
>    130             CNAME   130.128/26.2.0.192.in-addr.arpa.
>    131             CNAME   131.128/26.2.0.192.in-addr.arpa.
>    ;
>    ;  <<192-255>> /26
>    192/26          NS      ns.C.domain.
>    192/26          NS      some.other.third.name.server.
>    ;
>    193             CNAME   193.192/26.2.0.192.in-addr.arpa.
>    194             CNAME   194.192/26.2.0.192.in-addr.arpa.
>    195             CNAME   195.192/26.2.0.192.in-addr.arpa.
> ---------------------------------------
> 
> It doesn't seem to make sense with the NS entries pointing to
> the name servers that those chunks (/lengths) are being
> deligated to. Wouldn't each respective NS server(s) handle it
> instead. The CNAME is just an alias, right, so is it needed
> here? As a fall back messure? Unless I've missed something,
> the RFC doesn't seem to expalin that.
> Thanks.
> 
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> 
-- 
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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