Re: Long AS Path

[Mel Beckman <mel () beckman org>]

Steinar,

What reason is there to filter them? They are not a significant fraction of BGP paths. They cause no harm. It's just 
your sense of tidiness. 

You might consider contacting one of the operators to see if they do have a good reason you haven't considered. But 
absent a good reason *to* filter them, I would let BGP mechanics work as intended.

 -mel beckman

On Jun 21, 2017, at 12:57 AM, "sthaug () nethelp no" <sthaug () nethelp no> wrote:

> > Just wondering if anyone else saw this yesterday afternoon ?
> >
> > Jun 20 16:57:29:E:BGP: From Peer 38.X.X.X received Long AS_PATH=3D AS_SEQ(2=
> > ) 174 12956 23456 23456 23456 23456 23456 23456 23456 23456 23456 23456 234=
> > 56 23456 23456 23456 23456 23456 23456 23456 23456 23456 23456 23456 23456 =
> > 23456 23456 23456 23456 23456 ... attribute length (567) More than configur=
> > ed MAXAS-LIMIT
>
> There are quite a few examples of people using stupidly long AS paths.
> For instance
>
> 177.23.232.0/24    *[BGP/170] 00:52:40, MED 0, localpref 105
>                      AS path: 6939 16735 28163 28163 28163 28163 28163 28163 28163 28163 28163 28163 28163 28163 
> 28163 28163 28163 28163 262401 262401 262401 262401 262401 262401 262401 262401 262401 262401 262401 262401 262401 
> 262401 262401 262401 262949 52938 52938 52938 52938 52938 52938 52938 52938 52938 52938 52938 I
>
> I currently have 27 prefixes in my Internet routing table with 40 or
> more ASes in the AS path (show route aspath-regex ".{40,}").
>
> I see no valid reason for such long AS paths. Time to update filters
> here. I'm tempted to set the cutoff at 30 - can anybody see a good
> reason to permit longer AS paths?
>
> Steinar Haug, Nethelp consulting, sthaug () nethelp no