[54115] in North American Network Operators' Group
Re: FW: /8s and filtering
daemon@ATHENA.MIT.EDU (David Schwartz)
Tue Dec 10 15:41:31 2002
From: David Schwartz <davids@webmaster.com>
To: <hnarayan@cs.ucsd.edu>, <nanog@merit.edu>
Date: Tue, 10 Dec 2002 12:40:58 -0800
In-Reply-To: <Pine.GSO.4.32.0212101124290.13597-100000@gradlab.ucsd.edu>
Errors-To: owner-nanog-outgoing@merit.edu
On Tue, 10 Dec 2002 11:32:03 -0800 (PST), Harsha Narayan wrote:
>Now I am confused because I have got two sets of contradicting=
answers.
=09Because there are two questions, one about provider independent=
space and
one about space allocated by an ISP to its customer.
>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?
=09Anyone can multihome. There is no size requirement (except=
perhaps of your
budget).
>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?
=09No, because multihoming does not require that anyone but your=
direct
providers see your route. Since you pay them, you aren't imposing=
any costs
on anyone else.
=09The people you don't pay can choose to accept your small route=
or not.
Either way, you can reach them and they can reach you. Their=
route to you may
not be optimum, but that's their choice. If you want them to hear=
your route,
you can pay them to do so. It will work either way.
=09To repeat:
=091) Small multihomers should get IP address space from their most=
reliable
provider. This is the one they trust the most and intend to=
remain with the
longest.
=092) Small multihomers must get the ISP that assigns them address=
space to
allocate them at least a /24 (with multihoming as the=
justification if
needed). The ISP must agree to allow them to advertise their=
allocation
through other providers and must agree to hear and announce the=
block from
the customer *and* *other* *ISPs*.
=093) The ISP that assigns you IPs must prefer the more specific=
route from
their peers if they don't hear it directly from the multihomer.
=094) Small multhomers must get their other provider(s) to agree to=
hear their
announcement and readvertise it.
=095) Multihoming should be done only by those reasonably competent=
and
experienced. You probably can't get enough help from a mailing=
list and may
wind up signing contracts or purchasing equipment that harms=
you.
=09DS
