filtering /48 is going to be necessary

Sat Mar 10 06:48:31 UTC 2012

On Mar 9, 2012, at 7:08 PM, George Bonser wrote:

>> Owen said:
>> 
>> I'm not a big fan, either, but, I think that the concept of "be
>> conservative in what you announce and liberal in what you accept" has
>> to apply in this case. Since it is a common (quasi-)legitimate
>> practice, arbitrarily filtering it is ill-advised IMHO.
> 
> While I agree in principle, 16 bits of disaggregation has the potential for a lot of mayhem and 32 bits (accepting /64 from PA) would be catastrophic.  This would seem to be a case where upstream providers can assist the end user in obtaining their own PI space if they wish to multihome.  It would be in the provider's interest as it would reduce the number of potential complaints from customers concerning multihoming problems.
> 
> I filter /32 from PA space and am currently filtering one route but since the aggregate it is from has the same next hop and since I don't see the route from anyone else, I'm not worried about it.

I haven't heard anyone advocate accepting less than a /48. I think /48 is a reasonable "You must be this tall to ride" barrier.

Beyond that, YMMV.

Owen