nanog mailing list archives
Re: Longest prepend( 255 times) as path found
From: Mike Leber via NANOG <nanog () nanog org>
Date: Sun, 28 Aug 2022 03:27:18 -0700
Here's a related good article: "Excessive BGP AS-PATH prepending is a self-inflicted vulnerability" https://blog.apnic.net/2019/07/15/excessive-bgp-as-path-prepending-is-a-self-inflicted-vulnerability/You probably should not use a limit greater than 50 unless you want to encourage this behavior.
There have been previous substantive discussions on network operator mailing lists regarding why to use one specific limit or another.
Unfortunately I wasn't able to find the discussion thread that I remember that represented some consensus among backbones roughly around 50, so instead here are various random configuration examples that use "bgp maxas-limit 50"
https://www.nl-ix.net/nocdoc/ https://www.barryodonovan.com/wp-content/uploads/2019/04/BGP-101.pdf https://www.ciscopress.com/articles/article.asp?p=1312796&seqNum=3 https://www.networkworld.com/article/2234109/cisco-subnet-practical-bgp-security.html (etc... there are more)Excessive AS path prepending is a waste of global resources (router CPU, bandwidth, and memory in all the BGP speaking routers in the world with a full table).
On 8/24/22 7:00 PM, anonymous wrote:
Hey everyone, Too many hops found as below. Usually What shoud we do ? Should we filter it ? 91.246.12.0/24 <http://91.246.12.0/24>AS path: 4788 9002 41313 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 IAS path: 9930 9002 41313 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 51196 I/noname
Current thread:
- Longest prepend( 255 times) as path found anonymous (Aug 25)
- Re: Longest prepend( 255 times) as path found Alistair Mackenzie (Aug 25)
- Re: Longest prepend( 255 times) as path found Chriztoffer (Aug 25)
- Re: Longest prepend( 255 times) as path found Alejandro Acosta (Aug 25)
- Re: [External] Re: Longest prepend( 255 times) as path found Hunter Fuller via NANOG (Aug 25)
- Re: Longest prepend( 255 times) as path found Tom Beecher (Aug 25)
- Re: Longest prepend( 255 times) as path found Jeff Tantsura (Aug 25)
- Re: Longest prepend( 255 times) as path found Lincoln Dale (Aug 26)
- Re: Longest prepend( 255 times) as path found Tom Beecher (Aug 27)
- Re: Longest prepend( 255 times) as path found William Herrin (Aug 26)
- Re: Longest prepend( 255 times) as path found Mike Leber via NANOG (Aug 28)
- Re: Longest prepend( 255 times) as path found Alistair Mackenzie (Aug 25)