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North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical RE: BGP Filtering
Ben, Look here. They show an example of prefix filtering on the 128.0.0.0/8 network. I would assume you could extrapolate and come up with your own rule. http://www.cisco.com/en/US/docs/ios/12_0/np1/configuration/guide/1cbgp.h tml#wp7487 Mike Walter, MCP Systems Administrator 3z.net a PCD Company http://www.3z.net -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Ben Butler Sent: Tuesday, January 15, 2008 11:45 AM To: [email protected] Subject: RE: BGP Filtering 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 -----Original Message----- From: Jason Dearborn [mailto:[email protected]] 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 <[email protected]> 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 > 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? > > > Kind Regards > > Ben >
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