BGP Filtering

Joe Abley jabley at ca.afilias.info
Tue Jan 15 17:07:10 UTC 2008



On 15-Jan-2008, at 11:40, Ben Butler wrote:

> Defaults wont work because a routing decision has to be made, my  
> transit
> originating a default or me pointing a default at them does not
> guarantee the reachability of all prefixes..

Taking a table that won't fit in RAM similarly won't guarantee  
reachability of anything :-)

Filter on assignment boundaries and supplement with a default. That  
ought to mean that you have a reasonable shot at surviving de-peering/ 
partitioning events, and the defaults will pick up the slack in the  
event that you don't.

For extra credit, supplement with a bunch of null routes for bogons so  
packets with bogon destination addresses don't leave your network, and  
maybe make exceptions for "golden prefixes".

> I am struggling to see a defensible position for why just shy of 50%  
> of
> all routes appears to be mostly comprised of de-aggregated routes when
> aggregation is one of the aims RIRs make the LIRs strive to  
> achieve.  If
> we cant clean the mess up because there is no incentive than cant I
> simply ignore the duplicates.

You can search the archives I'm sure for more detailed discussion of  
this. However, you can't necessarily always attribute the presence of  
covered prefixes to incompetence.


Joe



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