Re: Filter subnets

From: Shane Amante (shane@amante.org)
Date: Thu Dec 14 2000 - 12:58:05 EST


On Thu, Dec 14, 2000 at 04:39:41PM +0800, Miguel A.L. Paraz wrote:
> On Wed, Dec 13, 2000 at 11:59:22PM -0600, Basil Kruglov wrote:
> Let me demonstrate what I would like.
>
> Customer A has 203.176.8.0/24 and ASN 9442. They are dual-homed to us and
> provider B. We have private peering with B.
>
> I hear this route both from the customer peer and private peering with B,
> such that if the customer link to us goes down we can still reach them.
>
> We have an upstream C who permits 203.176.8.0/24. However, we would only
> like to announce A's route if it was heard from the customer directly.
>
> If it was heard through peering with B, I don't want to send it out to C
> since if I do, I will be doing transit for A via B.
>
> I think there is no filter that matches (203.176.8.0/24 and _9442$), right?
> So I should instead mark incoming routes with communities and match them?

This would be the easiest method. Set the prefix coming to you from
peer B with an arbitrary community-string. Then, don't advertise that
prefix marked with the community-string to all your
upstreams/non-customer-peers.

> BTW. What is the best current practice for communities?
>
> Thanks.



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