[77662] in North American Network Operators' Group
Re: long as path games?
daemon@ATHENA.MIT.EDU (william(at)elan.net)
Mon Jan 31 13:12:08 2005
Date: Mon, 31 Jan 2005 10:16:50 -0800 (PST)
From: "william(at)elan.net" <william@elan.net>
To: Blaine Christian <blaine@blaines.net>
Cc: Jared Mauch <jared@puck.nether.net>,
Hank Nussbacher <hank@mail.iucc.ac.il>, Jon Lewis <jlewis@lewis.org>,
<nanog@nanog.org>
In-Reply-To: <BE23ACF5.A464%blaine@blaines.net>
Errors-To: owner-nanog-outgoing@merit.edu
Well, long as-path of 100 is certain to be invalid (result of misconfig if
not direct probe for vulnerability). Would it be good to recommend for
ISPs filter at some as-path size as its easy easy and does not consume
router resources? Would would be good as-path size to filter on, just to
be certain no valid route is filtered (just in case allow possible growth
of as-path up to 2x what it is now)?
On Mon, 31 Jan 2005, Blaine Christian wrote:
> Specifically, they have the ability to tickle a legacy cisco bug with AS
> path length. This bug was supposedly mitigated in code and I believe my
> previous company is still filtering AS path length (UUNET) of 100 or
> greater.
>
> A valid AS-Path of greater than 100 has not yet been found (which was why
> the filters were in place).
>
> On 1/31/05 8:53 AM, "Jared Mauch" <jared@puck.nether.net> wrote:
>
> > On Mon, Jan 31, 2005 at 07:19:14AM +0200, Hank Nussbacher wrote:
> >>
> >> At 10:23 PM 30-01-05 -0500, Jon Lewis wrote:
> >>
> >>> Someone at fido.net having some bgp config issues?
> >>
> >> Looks like someone probing for a buffer overflow on a world-wide basis.
> >>
> >> -Hank
> >>
> >>
> >>> Jan 30 18:34:51 EST: %BGP-6-ASPATH: Long AS path 6461 3356 6770 8282 8282
> >>> 8282 8282 8282 8282 8282 8282 8282 8282 8282 8282 8282 8282 8282 8282 8282
> >>> 8282 8282 8282 8282 8282 8282 8282 8282 8282 8282 8282 8282 8282 8282 8282
> >>> 8282 8282 8282 8282 8282 8282 8282 8282 8282 8282 8282 8282 8282 8282 8282
> >>> 8282 8282 8282 8282 8282 8282 8282 8282 8282 8282 8282 8282 8282 8282 8282
> >>> 8282 8282 8282 8282 8282 8282 8282 8282 8282 8282 8282 8282 8282 8282 8282
> >>> 8282 8282 8282 8282 8282 8282 8282 8282 8282 8282 8282 8282 8282 8282 8282
> >>> received from ...
> >
> > Router(config-router)#bgp maxas-limit ?
> > <1-2000> Number of ASes in the AS-PATH attribute
> >
> > Router(config-router)#bgp maxas-limit 50
> >
> > Easy to fix/reject.
> >
> > - jared
