[126539] in North American Network Operators' Group
Re: BGP Transit AS
daemon@ATHENA.MIT.EDU (joel jaeggli)
Thu May 20 16:34:45 2010
Date: Thu, 20 May 2010 13:33:58 -0700
From: joel jaeggli <joelja@bogus.com>
To: Rafael Ganascim <rganascim@gmail.com>
In-Reply-To: <AANLkTikgqsXwFd-7ta7fqnXRwr01E0l8yPrUbKvZs-6b@mail.gmail.com>
Cc: nanog@nanog.org
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
On 2010-05-20 11:25, Rafael Ganascim wrote:
> 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.
>
>
> NSP 1 ------------------ ISP 1 Router2 ----------- NSP 2
> | |
> | |
> | |
> | annunce /21 |
> | |
> Customer1 --------------- ISP 1 Router1
> 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...
longest match wins...
if you're customer 1
deaggregate the avertisement to isp 1 or re-aggregate the advertisement
to nsp 1. either will achieve the same end.
if you're isp1 consider what customer 1 was trying to achieve by doing
this. e.g. they're traffic engineering (or they are clueless) and
theirfore have a vested interest in the current path.
> Is this solution right ? What is the better solution for this
> scenario? How large ISPs solve this kind of problem?
>
>
> Thanks,
>
> Rafael
>
