Re: BGP prefix filter list

["Jörg Kost" <jk () ip-clear de>]

Hi,

I did this tool a few years ago to download and built ASN filter lists 
by region automatically:

https://github.com/ipcjk/asnbuilder/releases

The tricky part was to build regular expressions for devices, that don't 
understand number ranges.

For some of our routers we (un)select ASNs manually by reading and 
comparing CIDR-reports to current Sflow traffic:

E.g.
https://github.com/ipcjk/asnbuilder/blob/master/customASN.txt
will become
https://github.com/ipcjk/asnbuilder/blob/master/saveTheFIB.txt

Jörg


On 17 May 2019, at 10:59, Jared Brown wrote:

> There are a few approaches to culling the routing table. You can do it 
> either statically or dynamically, according to your needs.
>
> 1. Filtering based on upstream communities
>
> Slimming down the Internet routing table
> https://www.redpill-linpro.com/sysadvent/2016/12/09/slimming-routing-table.html
>
>
> 2. Filtering based on region
>
> BGP filter for North American routes
> http://gregsowell.com/?p=5505
>
> Substitute prefixes for applicable region(s). Each region is about 
> 200k prefixes. For more granularity use a geolocation service to 
> select prefixes and/or ASNs.
>
>
> 3. Using flow information to install only top routes
>
> SDN Internet Router – Part 2
> https://labs.spotify.com/2016/01/27/sdn-internet-router-part-2/
> https://blog.ipspace.net/2015/01/sdn-router-spotify-on-software-gone-wild.html
>
>
> 4. Aggregate the routing table
>
> According to the weekly routing table report you can aggregate 
> announcements to about half the number of prefixes. You need to roll 
> your own software to preprocess the BGP feed. There are some tools out 
> there, but I couldn't find a blog post about it with a quick search. 
> If you have one, please share!
>
>
>
> Jared