FW: /8s and filtering

Harsha Narayan hnarayan at cs.ucsd.edu
Tue Dec 10 22:03:17 UTC 2002


Hello,
  Yes, it is all classless now, but I saw Verio's policies and thought
that it is the way ISPs filter. Also, the Jippi group filters at /21
except in the 192.0/7 space (where it is a /24). I didn't have enough
knowledge to realize that classful was "vestigal".

Thanks,
Harsha.

On Tue, 10 Dec 2002 bmanning at vacation.karoshi.com wrote:

>
>  but there is no "class C space" anymore. there is no "class A space"
>  either.  its all CIDR space and some providers have retained some
>  vestigal classfull concepts in the creation/maintaince of their routing
>  filters. a /24 may or may not get you past my filters.  any you'll have
>  no way to know until/unless you try to get to my sites or we develop
>  a peering relationship.
>
>  wrt the evolution of filters. yes, they do evolve. and so does ARIN
>  policy. you presume too much to second guess that ARIN policy will
>  evolve in the way you outline.
>
>
> >
> > Hello,
> >   Thank you very much everyone for all your replies. When Class C space
> > gets used up, wouldn't the filtering policies have to change to allow the
> > same kind of multihoming from the Class A space. Currently, a /24 from
> > Class C is enough to get past filters. However later, a /22 (or is it /20)
> > from Class A would be required to get past filters.
> >
> >   Since there are only three /8s left in Class C, I was curious whether
> > filtering policies would change to accommodate this.
> >
> >   If filtering policies won't change ARIN will have to change its
> > multihoming PA policy to giving away a /22 instead of a /24. Though
> > officially it is RIR policy not to worry about the routability of an
> > a prefix I guess they do worry about it?
> >
> > Thanks,
> > Harsha.
> >
> >
> > On Tue, 10 Dec 2002 bmanning at vacation.karoshi.com wrote:
> >
> > > >
> > > >
> > > > Hello,
> > > >   Now I am confused because I have got two sets of contradicting answers.
> > > > Some say that anyone can multihome, some say that you need to be of a
> > > > certain minimum size to multihome. May I know what is the right answer?
> > > >
> > > >   I agree that allowing anyone to multihome would increase the size of the
> > > > routing table. So does this mean that someone has to be of a certain size
> > > > to multihome?
> > > >
> > > > Harsha.
> > > >
> > >
> > > 	anyone can multihome, with the cooperation of others.
> > > 	current practice seems to dictate that the standard
> > > 	operating procedures to protect the integrity of
> > > 	the routing system mandate that only prefixes of
> > > 	certain lengths are allowed at -SOME- isp boundaries.
> > >
> > > 	you seem to have the assumption that there is a single
> > > 	standard here.  There is not.
> > >
> > > --bill
> > >
> >
> >
> >
> >
>




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