[c-nsp] BGP route filtering question about upstreams

[Andrew (Andy) Ashley]

> f AS200 is running two separate routing tables, I would expect them to have
two ASes - and you would peer with either one or both of them.
Interestingly, AS200 doesn't have two separate ASes.
There are two eBGP sessions to them, to different routers (I assume) and
they split the table, I guess based on local peering routes or something
similar.

>If AS200 (International) is a transit customer of  AS300, and AS300 breaks
their routing, you may still end having an issue with how AS200 routes their
traffic outbound
Correct. This is precisely what AS100 wants to avoid.

>AS200 (International) may offer you communities that you can add to your
announcements that would allow you to increase the AS PATH between AS200 and
AS300 for your networks.
Neither AS200 or AS300 offer communities to customers, so that is
unfortunately not an option.

Thanks
Andrew

From:  Andrew Miehs <andrew at 2sheds.de>
Date:  Tuesday 07 October 2014 at 15:56
To:  Andrew Ashley <andrew.a at aware.co.th>
Cc:  "mark.tinka at seacom.mu" <mark.tinka at seacom.mu>,
"cisco-nsp at puck.nether.net" <cisco-nsp at puck.nether.net>
Subject:  Re: [c-nsp] BGP route filtering question about upstreams

On Wed, Oct 8, 2014 at 12:27 AM, Andrew (Andy) Ashley <andrew.a at aware.co.th>
wrote: 
> 
> Apologies, I should have clarified here:
> AS200 operates both a domestic and an international BGP routing table.
> AS300 operates a combined BGP routing table.
> The scenario is concerned with international routing only.
> AS200 should still provide routes to AS300 and its customers via the
> domestic table.
> The idea is to avoid international paths over AS200 ending up on the AS300
> international backbone (since AS200 is also a transit customer of AS300).

If AS200 is running two separate routing tables, I would expect them to have
two ASes - and you would peer with either one or both of them.

If AS200 (International) is a transit customer of  AS300, and AS300 breaks
their routing, you may still end having an issue with how AS200 routes their
traffic outbound... AS200 (International) may offer you communities that you
can add to your announcements that would allow you to increase the AS PATH
between AS200 and AS300 for your networks.

So based on this, I would assume you peer with AS200, AS201 (Domestic
version of 200) and AS300. For you it would be like peering with 3 different
companies.


Andrew