nanog mailing list archives
Re: Long AS Path
From: Steve Lalonde <steve () enta net>
Date: Wed, 21 Jun 2017 17:50:27 +0100
Mel, There was a Cisco bug many years ago that caused lots of issues. Since then we have limited max-as to 50 and it has not caused any reported issues yet. Link that does not require a CCO login to view. http://blog.ipspace.net/2009/02/oversized-as-paths-cisco-ios-bug.html Regards Steve Lalonde
On 21 Jun 2017, at 16:49, Mel Beckman <mel () beckman org> wrote: 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-LIMITThere 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
Current thread:
- Re: Long AS Path, (continued)
- Re: Long AS Path Pierfrancesco Caci (Jun 21)
- Re: Long AS Path jim deleskie (Jun 22)
- Re: Long AS Path Mel Beckman (Jun 22)
- Re: Long AS Path Mel Beckman (Jun 21)
- Re: Long AS Path Bob Evans (Jun 21)
- Re: Long AS Path Saku Ytti (Jun 21)
- Re: Long AS Path Jon Lewis (Jun 22)
- Re: Long AS Path Stephen Satchell (Jun 22)
- Re: Long AS Path Ryan L (Jun 23)
- Re: Long AS Path Tom Beecher (Jun 21)
- Re: Long AS Path Steve Lalonde (Jun 22)
- Re: Long AS Path James Bensley (Jun 23)
- Re: Long AS Path Mel Beckman (Jun 23)
- Re: Long AS Path James Bensley (Jun 24)
- Re: Long AS Path Mel Beckman (Jun 24)
- Re: Long AS Path James Bensley (Jun 25)
- Re: Long AS Path Hunter Fuller (Jun 26)
- RE: Long AS Path Michael Hare (Jun 26)
- Re: Long AS Path Mel Beckman (Jun 26)
- RE: Long AS Path Jerry Cloe (Jun 26)