BGP prefix filter list

Wed May 15 13:46:33 UTC 2019

If you have multiple transit providers and still want to be able to push traffic to the best path (no default route), then maybe a filter that will accept only AS Path 2/3 or shorter per transit provider, and a default route for the rest. You will get significantly less prefixes, and BGP path selection will work “locally”. For far away prefixes though (more than 4 ASes away), you will not (always) pick the best path.

> On 15 May 2019, at 16:36, Dan White <dwhite at olp.net> wrote:
> 
> We recently filtered out >=/24 prefixes since we're impacted by 768k day.
> I'm attaching our lightly researched list of exceptions. I'm interested in
> what others' operational experience is with filtering in this way.
> 
> Filtering /24s cut our table down to around 315K.
> 
> On 05/15/19 13:43 +0200, Baldur Norddahl wrote:
>> Hello
>> 
>> 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 similar?
>> 
>> 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.
>> 
>> Thanks,
>> 
>> Baldur
>> 
> 
> -- 
> Dan White
> BTC Broadband
> Network Admin Lead
> Ph  918.366.0248 (direct)   main: (918)366-8000
> Fax 918.366.6610            email: dwhite at mybtc.com
> http://www.btcbroadband.com
> <punt-768k-day.txt>