BGP prefix filter list

Mike Hammett nanog at
Wed May 15 18:52:48 UTC 2019

You can't do uRPF if you're not taking full routes. 

You also have a more limited set of information for analytics if you don't have full routes. 

Mike Hammett 
Intelligent Computing Solutions 


----- Original Message -----

From: "Ca By" <cb.list6 at> 
To: "Dan White" <dwhite at> 
Cc: nanog at 
Sent: Wednesday, May 15, 2019 1:50:41 PM 
Subject: Re: BGP prefix filter list 

On Wed, May 15, 2019 at 7:27 AM Dan White < dwhite at > wrote: 

On 05/15/19 13:58 +0000, Phil Lavin wrote: 
>> We're an eyeball network. We accept default routes from our transit 
>> providers so in theory there should be no impact on reachability. 
>> I'm pretty concerned about things that I don't know due to inefficient 
>> routing, e.g. customers hitting a public anycast DNS server in the wrong 
>> location resulting in Geolocation issues. 
>Ah! Understood. The default route(s) was the bit I missed. Makes a lot of 
>sense if you can't justify buying new routers. 
>Have you seen issues with Anycast routing thus far? One would assume that 
>routing would still be fairly efficient unless you're picking up transit 
>from non-local providers over extended L2 links. 

We've had no issues so far but this was a recent change. There was no 
noticeable change to outbound traffic levels. 

+1, there is no issue with this approach. 

i have been taking “provider routes” + default for a long time, works great. 

This makes sure you use each provider’s “customer cone” and SLA to the max while reducing your route load / churn. 

IMHO, you should only take full routes if your core business is providing full bgp feeds to downstrean transit customers. 


Dan White 
BTC Broadband 
Network Admin Lead 
Ph 918.366.0248 (direct) main: (918)366-8000 
Fax 918.366.6610 email: dwhite at 


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