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, "sth...@nethelp.no" <sth...@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, sth...@nethelp.no
