nanog mailing list archives
Re: Networks ignoring prepends?
From: Robert Raszuk <robert () raszuk net>
Date: Wed, 24 Jan 2024 10:41:57 +0100
Bill,
https://datatracker.ietf.org/doc/html/rfc4271#section-9.1.2.2 "a) Remove from consideration all routes that are not tied for having the smallest number of AS numbers present in their AS_PATH attributes." So literally, the first thing BGP does when picking the best next hop is to discard all but the routes with the shortest AS path.
Not really. I have never seen a BGP implementation which would do that. That section 9 you are referring to is just informational - no specific order in there is mandated. Shortest AS-PATH is used as step 4 or 5 in best path selection - not to mention Cost Communities which below links do not even consider: https://www.cisco.com/c/en/us/support/docs/ip/border-gateway-protocol-bgp/13753-25.html https://www.juniper.net/documentation/us/en/software/junos/vpn-l2/bgp/topics/concept/routing-protocols-address-representation.html Thx, R.
Current thread:
- Re: Networks ignoring prepends?, (continued)
- Re: Networks ignoring prepends? Jay Borkenhagen (Jan 23)
- Re: Networks ignoring prepends? Owen DeLong via NANOG (Jan 23)
- Re: Networks ignoring prepends? William Herrin (Jan 23)
- Re: Networks ignoring prepends? Chris Adams (Jan 23)
- Re: Networks ignoring prepends? Niels Bakker (Jan 23)
- Re: Networks ignoring prepends? William Herrin (Jan 23)
- Re: Networks ignoring prepends? Tom Beecher (Jan 23)
- Re: Networks ignoring prepends? William Herrin (Jan 23)
- Re: Networks ignoring prepends? Chris Adams (Jan 23)
- Re: Networks ignoring prepends? William Herrin (Jan 23)
- Re: Networks ignoring prepends? Robert Raszuk (Jan 24)
- Re: Networks ignoring prepends? James Jun (Jan 24)
- Re: Networks ignoring prepends? Chris Adams (Jan 24)
- Re: Networks ignoring prepends? William Herrin (Jan 24)
- Re: Networks ignoring prepends? Chris Adams (Jan 24)
- Re: Networks ignoring prepends? Majdi S. Abbas (Jan 23)
- Re: Networks ignoring prepends? Owen DeLong via NANOG (Jan 24)
- Re: Networks ignoring prepends? William Herrin (Jan 24)
- Re: Networks ignoring prepends? Owen DeLong via NANOG (Jan 24)
- Re: Networks ignoring prepends? Tom Beecher (Jan 23)
- Re: Networks ignoring prepends? William Herrin (Jan 23)