[101655] in North American Network Operators' Group
BGP Filtering
daemon@ATHENA.MIT.EDU (Ben Butler)
Tue Jan 15 11:10:18 2008
Date: Tue, 15 Jan 2008 16:11:36 -0000
From: "Ben Butler" <ben.butler@c2internet.net>
To: <nanog@merit.edu>
Errors-To: owner-nanog@merit.edu
Hi,
Considering:
http://thyme.apnic.net
Total number of prefixes smaller than registry allocations: 113220
!!!!!
/20:17046 /21:16106 /22:20178 /23:21229 /24:126450
That is saying to me that a significant number of these smaller prefixes
are due to de-aggregation of PA and not PI announcements.
My question is - how can I construct a filter / route map that will
filter out any more specific prefixes where a less specific one exists
in the BGP table.
If my above conclusion is correct a significant portion ~47% of the
number of the prefixes in the table could be argued to be very
unnecessary at one level or another.
Is such a filter possible easily or would it have to be explicitly
declared, any chance of a process the automatically tracks and publishes
a list of offending specifics similar to Team Cymru's Bogon BGP feed.
As a transit consumer - why would I want to carry all this cr*p in my
routing table, I would still be getting a BGP route to the larger prefix
anyway - let my transit feeds sort out which route they use & traffic
engineering.
Thoughts anyone?=20
Kind Regards
Ben
