[126536] in North American Network Operators' Group
BGP Transit AS
daemon@ATHENA.MIT.EDU (Rafael Ganascim)
Thu May 20 14:25:20 2010
Date: Thu, 20 May 2010 15:25:04 -0300
From: Rafael Ganascim <rganascim@gmail.com>
To: nanog@nanog.org
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
Hi all,
I have a doubt about the bellow scenario, where the ISP1 use eBGP
sessions to its peers and is a BGP Transit AS.
=A0NSP 1 ------------------ ISP 1 Router2 ----------- NSP 2
=A0 |=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=
=A0=A0=A0=A0=A0 |
=A0 |=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=
=A0=A0=A0=A0=A0 |
=A0 |=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=
=A0=A0=A0=A0=A0 |
=A0 | annunce /21=A0=A0=A0=A0=A0=A0=A0=A0=A0 |
=A0 |=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=
=A0=A0=A0=A0=A0 |
=A0Customer1 --------------- ISP 1 Router1
=A0=A0=A0=A0=A0=A0=A0=A0=A0 announce /20
The "Customer1" is client on both ISPs (ISP1 and NSP1) and have an /20
IP prefix. To NSP1, it announce two /21 prefixes. To ISP1, it announce
a /20 prefix. If traffic comes from NSP 2 (connected only to ISP 1) to
Customer1, the ISP 1 Routers try to send data over NSP 1, ignoring the
Custormer1->ISP1 link.
To solve this question, an solution that I found is filter Customer1
prefixes in BGP session between NSP1 and ISP1 Router2. But this don't
appear scalable...
Is this solution right ? What is the better solution for this
scenario? How large ISPs solve this kind of problem?
Thanks,
Rafael
