[101658] in North American Network Operators' Group
RE: BGP Filtering
daemon@ATHENA.MIT.EDU (Ben Butler)
Tue Jan 15 11:44:12 2008
Date: Tue, 15 Jan 2008 16:45:24 -0000
From: "Ben Butler" <ben.butler@c2internet.net>
To: <nanog@merit.edu>
Errors-To: owner-nanog@merit.edu
Hi Jason,
Fantastic news, it is possible. We are using Cisco - would you be so
kind as to give me a clue into which bit of Cisco's website you would
like me to read as I have already read the bits I suspected might tell
me how to do this but have guessed wrong / the documentation hasn't
helped - so a handy pointer would be appreciated.
Kind Regards
Ben=20
-----Original Message-----
From: Jason Dearborn [mailto:jasondearborn@gmail.com]=20
Sent: 15 January 2008 16:35
To: Ben Butler
Subject: Re: BGP Filtering
That's typically a function of your router software. Juniper, Force10,
and Cisco all have support for this. Check your manual.
On Jan 15, 2008 8:11 AM, Ben Butler <ben.butler@c2internet.net> wrote:
>
> 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=20
> 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=20
> 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=20
> number of the prefixes in the table could be argued to be very=20
> unnecessary at one level or another.
>
> Is such a filter possible easily or would it have to be explicitly=20
> declared, any chance of a process the automatically tracks and=20
> 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=20
> routing table, I would still be getting a BGP route to the larger=20
> prefix anyway - let my transit feeds sort out which route they use &=20
> traffic engineering.
>
> Thoughts anyone?
>
>
> Kind Regards
>
> Ben
>
