North American Network Operators Group

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Re: multi-homing fixes

  • From: Paul Schultz
  • Date: Fri Aug 24 23:13:15 2001

On Fri, 24 Aug 2001, Steve Noble wrote:

> Now that's confusing.. doesn't CIDR supposedly make it so that one IP is
> no better or worse then another?  Why do people base their filtering policies
> on where things are in the "Classful" space?  How is 64/8 any different then
> 216/8.. they allocate out of both of them, it's a crapshoot what you get
> since ARIN denys responsibility to provide routable IP space, yet there is
> space that is "more" routable than other space.

If we must filter based on minimum allocation boundaries, a new
"classful" definition of networks is exactly what we need.  Many carriers
that have /16's or bigger out of 6x/8 slice and dice it up into multiple
/19's and /20's.  How is this different from me slicing a /20 up into 16
individual /24's? It's still someone advertising 16 prefixes instead of
one, and it causes just as much bloat.  but since the prefix lengths are
"small enough" to pass through the aggregation police it's for some reason
or another considered ok.

Unless the RIR's put something out along the lines of:

/16's and greater will be allocated out of x/8
/17's will be allocated out of x/8
/18's will be allocated out of x/9
/19's will be assigned out of x/10
/20's will be assigned out of x/10

the filtering methods talked about here will only be half as effective as
they should, and some of the worst offenders still get to bloat the tables
as much as always.  Sure it makes filtering more difficult, but hey if you
want to do it, do it right.  I know that many questions come up like "what
if i get a /20, then another contiguous /20 that can be summarized as a
/19" .. that just brings up more questions on how to address the current
problems of handing out address space.