Best practices inquiry: filtering 128/1

Tue Jul 11 21:22:16 UTC 2006

On 11-Jul-2006, at 02:06, Florian Weimer wrote:

> * Patrick W. Gilmore:
>
>> Actually, I take that back.  Why wouldn't you just get a feed from
>> Cymru <http://www.cymru.com/Bogons/index.html> ??
>
> I don't think Team Cymru offers a "feed" of what is supposed to be in
> the routing table.

No, but they offer a feed of what is not supposed to be there.

   http://www.cymru.com/BGP/bogon-rs.html

> The correct approach would be to verify prefixes using somewhat
> indepedent. more static data, such as RPSL data from RIRs.

That might be more correct in theory, but in practice it depends on  
RPSL data stored by RIRs being accurate. Although this is a  
reasonable dependency in some corners of the network, it's entirely  
impractical (on its own) if you're seeking to filter a full table.

As one of many contributing hints to whether a particular filter is  
worth accepting, it might be useful though (along the lines that  
SpamAssassin doesn't necessarily reply on any one reason to brand a  
message as spam, but builds a score based on all kinds of tests).  
There was a relevant presentation in LA:

   http://www.nanog.org/mtg-0510/deleskie.html

Joe