nanog mailing list archives
RE: FW: /8s and filtering
From: "Ejay Hire" <ejay.hire () isdn net>
Date: Tue, 10 Dec 2002 13:08:44 -0600
Having a /24 doesn't indicate you are a network of any particular size, 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 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 providers 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 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~
Current thread:
- Re: FW: /8s and filtering, (continued)
- Re: FW: /8s and filtering bmanning (Dec 10)
- Re: FW: /8s and filtering Harsha Narayan (Dec 10)
- Re: FW: /8s and filtering Stephen J. Wilcox (Dec 10)
- Re: FW: /8s and filtering bmanning (Dec 10)
- Re: FW: /8s and filtering David Schwartz (Dec 10)
- Re: FW: /8s and filtering Harsha Narayan (Dec 10)
- Re: FW: /8s and filtering N (Dec 10)
- Re: FW: /8s and filtering David Schwartz (Dec 10)
- Re: FW: /8s and filtering Tim Thorne (Dec 11)
- RE: FW: /8s and filtering Harsha Narayan (Dec 10)
- RE: FW: /8s and filtering Brian (Dec 10)
- RE: FW: /8s and filtering Harsha Narayan (Dec 10)
- RE: FW: /8s and filtering Brian (Dec 10)
- RE: FW: /8s and filtering Harsha Narayan (Dec 10)
- RE: FW: /8s and filtering Alec H. Peterson (Dec 10)
- RE: FW: /8s and filtering Harsha Narayan (Dec 10)