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Re: Delegating /24's from a /19

  • From: Robert Bonomi
  • Date: Tue Mar 15 15:42:02 2005

> From  Tue Mar 15 14:12:12 2005
> Date: Tue, 15 Mar 2005 15:12:10 -0500
> From: Robert Blayzor <>
> To:
> Cc: Mike Sawicki <fifi@HAX.ORG>,
> Subject: Re: Delegating /24's from a /19
> wrote:
> > Either by doing DNS delegation on the zone boundary or by SWIP'ing the 
> > space to the other company.
> You can SWIP it yes, but that won't help DNS on small blocks like /24's.
> > It is very easy to do DNS delegation, say if you have, and 
> > you want to delegate, in your zone file for 
> > zone put 
> > 
> > 1 IN	NS
> > 1 IN	NS
> The only way it will work is to use RFC2317 or slave the zones from the
> other name server.  Because he does not have the entire /16 you can't
> just delegate like that.

OK, what am I missing?

  The holder of the /16 _has_ delegated rDNS for the 32  /24s to the /19 owner.

The /19 owner can, on it's nameserver, run an "authoritative" zone for
the /16 -- with _its_ /24s listed explicitly, and a wildcard pointing 
back to the rDNS nameserver of the /16 owner.

"He who" queries from the outside world will work their way down from the
.arpa zone, to the  zone, get referred to the nameserver
at "thiscompany", and get referred to the NS listed for
which will resolve

"He who" queries the /19 owner nameserver directly for a 
address that lies within the /19 owner's addresses will get answered by
that nameserver, *or* be referred to the client's server. If they ask for
something *outside* the  /19 owner's space, the wildcard -- referring to
the 'upstream' (the /16 owner) nameserver kicks in.

_AS_LONG_AS_ the 'delegated to' nameserver has the wildcard in it pointing
back to the 'parent' nameserver, this seems to work just fine. Admittedly,
if the upstream block owner changes the _name_ of it's nameserver(s), the
'delegated to' nameserver  requires manual tweaking, but, realistically,
"how often" does _that_ happen?