[31170] in North American Network Operators' Group
Re: Confussion over multi-homing
daemon@ATHENA.MIT.EDU (John Fraizer)
Thu Sep 14 20:39:58 2000
Date: Thu, 14 Sep 2000 20:38:06 -0400 (EDT)
From: John Fraizer <nanog@EnterZone.Net>
To: Sean Donelan <sean@donelan.com>
Cc: nanog@merit.edu
In-Reply-To: <20000914214529.20385.cpmta@c004.sfo.cp.net>
Message-ID: <Pine.LNX.4.21.0009142033580.9472-100000@Overkill.EnterZone.Net>
MIME-Version: 1.0
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Errors-To: owner-nanog-outgoing@merit.edu
On 14 Sep 2000, Sean Donelan wrote:
>
> On Thu, 14 September 2000, Brantley Jones wrote:
> > 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.
>
> It could be filtered now. You just won't find out about it until you try
> to reach a particular site, or they try to reach you.
>
> There is no practical way to test if an address is being "globally routed."
> You could try testing every address in your route table, but there is no
> assurance your route table is complete.
>
>
>
Sean,
They won't see it even if their /20 announcement is being filtered as long
as their upstream is listening to it. (Upstream being the carrier they
obtained the /20 from.) This is because even though some ISP/NSPs may not
listen to the specific /20 announcement, I haven't found any who will
ignore a /19 or /17 announcement for the master block. As long as they
know how to get to that block, and teh "upstream" knows how to get to the
/20, the route filtering isn't going to be apparent at all... Until the
time that the "upstream" has connectivity issues.
---
John Fraizer
EnterZone, Inc
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