[rbak-nsp] New old BGP issue.

[Jeff Tantsura]

Hi Pawel,

SEOS has been treating this condition (AS path longer than 255) as withdraw
since 2003.
Could you please provide access to the PoC?

Thanks!

Jeff

On Fri, Dec 2, 2011 at 2:56 AM, Pawel Jarosz <pj at hostersi.pl> wrote:

> Hi,
> there is another BGP issue, known since 2008.
> Oversized as path causes BGP session to be torn down,
> this is ok from RFC point of view, but mostly inacceptable in public
> network.
> I have checked this on SEOS-6.4.1.3-Release, and the issue exists.
> PoC available on request.
>
> Cisco has resolved this:
> http://www.cisco.com/en/US/**docs/ios/12_3/release/notes/**123mcav2.html<http://www.cisco.com/en/US/docs/ios/12_3/release/notes/123mcav2.html>
>
> •CSCeh13489
> Symptoms: A router may reset its Border Gateway Protocol (BGP) session.
> Conditions: This symptom is observed when a Cisco router that peers with
> other routers receives an Autonomous System (AS) path with a length that is
> equal to or greater than 255.
>
> Workaround: Configure the bgp maxas limit command in such as way that the
> maximum length of the AS path is a value below 255. When the router
> receives an update with an excessive AS path value, the prefix is rejected
> and recorded the event in the log.
>
> Is there a way to avoid this strict RFC behavior in SeOS?
>
> Regards,
>        Pawel Jarosz
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