Interesting. Perhaps your source hasn't read the policy updates. Here is the link to ARIN's site, and I have successfully used this as justification for a customer. http://www.arin.net/policy/2001_2.html -ej -----Original Message----- From: Harsha Narayan [mailto:hnarayan@cs.ucsd.edu] Sent: Tuesday, December 10, 2002 1:15 PM To: Ejay Hire Cc: nanog@merit.edu Subject: RE: FW: /8s and filtering Hello, No, this is not the case. I enquired and it seems multihoming is not a justification for a /24 in any RIR. Does a network have to be able to fully utilize a /26 (25% of /24) in order to multihome? Harsha. On Tue, 10 Dec 2002, Ejay Hire wrote:
Having a /24 doesn't indicate you are a network of any particular
ARIN ratified a policy that allows multihoming as justification for a /24.
-ej
-----Original Message----- From: N [mailto:nathan@stonekitty.net] Sent: Tuesday, December 10, 2002 1:01 PM To: Forrest Cc: nanog@merit.edu Subject: Re: FW: /8s and filtering
comments inline
On Tue, Dec 10, 2002 at 12:36:39PM -0600, Forrest wrote:
I was also curious about this - if I am a customer who wants to multihome and can justify only a /24, I would go to an ISP which
has an
allocation from the Class C space rather than one from the Class A space.
It doesn't matter. For all practical purposes, basement multihomers only care that their two or three providers have their route.
Maybe I'm missing something, but what good would it do for someone to multihome if only their own providers accept their route, but nobody else does? I realize that their block should be still announced with
size, their
ISP's larger aggregate, but what good does this do if your ISP goes down and can't announce the large aggregate.
For the assigned block to be part of the same aggregate(of both providers), that implys that the providers sharing the responsibility for the aggregate. It happens, but is rare. In this case, the
must accept more specific routes from each other, that is within the space being aggregated. If they do not share specifics, one uplink down will cause a large percentage ~50% for the customer. This scenario is valid for load balancing, but redundancy is fragile. The only advantage I see is no limit to prefix length. You can do this with a /28 if you want... given the above caveats are addressed.
If you're a smaller organization, perhaps you'll only have a /23 from your upstream provider. With the filtering that seems to be in place, it seems like the only way you can truly multihome with a /23 is if it happens to be in the old Class C space. Or is this wrong?
In today's VLSM world... the old classes have no bearing on filtering in my experience. Prefix length discrimination knows no classfull boundaries.
What seems to be needed is perhaps a /8 set aside by the RIR specifically to allocate to small organizations that wish to multihome that
providers people
would accept /24 and shorter from.
There is value in the current filtering of longest prefixes... Allowing anyone to multihome with BGP, using any network size, is going to double our BGP tables overnight. Perhaps its good that you must be of some size to participate in public BGP. Many providers offer redundancy that is more appropriate for the smaller networks.
-- ,N
~Nathan - routing & switching dude/fly-boy/sport biker - San Jose CA~