[31198] in North American Network Operators' Group
Re: Confussion over multi-homing
daemon@ATHENA.MIT.EDU (dan@netrail.net)
Fri Sep 15 21:31:28 2000
Date: Fri, 15 Sep 2000 21:23:26 -0400 (EDT)
From: <dan@netrail.net>
To: Brantley Jones <bjones@redundant.net>
Cc: nanog@merit.edu
In-Reply-To: <4.3.2.7.0.20000914161858.02da0dc8@mrtg.redundant.net>
Message-ID: <Pine.LNX.4.10.10009152122020.11001-100000@macdaddy.netrail.net>
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Errors-To: owner-nanog-outgoing@merit.edu
Of course, peering agreements may speak to route filtering at that
particular interface, but can't assure global routability. For all intents
and purposes, /24s are globally routable, but their are several meaningful
exceptions - Verio and legacy class B space come to mind.
Daniel Golding
Director of R&D "I'm not evil. I'm just drawn that way"
NetRail, Inc.
1-888-NetRail
On Thu, 14 Sep 2000, Brantley Jones wrote:
>
> At 01:23 PM 9/14/2000 -0500, you wrote:
>
> >Wouldn't one of the ISPs have to advertise a longer prefix? I would think
> >that the address space would come from only one of the providers, in which
> >case the other provider would have to advertise this space on top of its own
> >/20. It is irrelevant whether the two ISPs advertise one another, the
> >longer prefix would be the first choice for the backbone traffic. If the
> >longer prefix route goes down, traffic would still go to the /20 the other
> >provider is advertising.
> >The ISP who is advertising the route on top of its own /20 can't aggregate
> >said route as it only can route to that portion of the address space defined
> >in the longer prefix.
> >
> >Geoff Zinderdine
>
> The problem is GETTING a /20 from anybody. We recently tried and could
> only get a /23 (being a small start-up). BUT, that /23 is (apparently)
> globally routable because of peering agreements with L3 and UUNET. Our /23
> prefix has yet to be filtered by anybody.
>
> Brantley
>
>
