BGP prefix filter list

Jared Brown nanog-isp at
Fri May 17 08:59:36 UTC 2019

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

2. Filtering based on region

BGP filter for North American routes

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

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!


On 05/15/19 13:43 +0200, Baldur Norddahl wrote:
>This morning we apparently had a problem with our routers not handling 
>the full table. So I am looking into culling the least useful prefixes 
>from our tables. I can hardly be the first one to take on that kind of 
>project, and I am wondering if there is a ready made prefix list or 
>Or maybe we have a list of worst offenders? I am looking for ASN that 
>announces a lot of unnecessary /24 prefixes and which happens to be 
>far away from us? I would filter those to something like /20 and then 
>just have a default route to catch all.

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