Re: What is BCP re De-Aggregation: strict filtering /48s out of /32 RIR minimums.

[Suresh Ramasubramanian <ops.lists () gmail com>]

On Wed, Nov 14, 2012 at 6:40 PM, Ben S. Butler <Ben.Butler () c2internet net>wrote:

> 3>     Don't use filters, generate it from an IRR?
>
> Given there is no "right" answer what is considered to be the best fit one?


This sounds like your best bet.  Assuming you can find an IRR with
comprehensive enough coverage.

The other option is of course "don't filter based solely on RIR minimum
assignments" ..

I know at least some ISPs (like swisscom) do this for v4 too, but that
simply means people who try to multihome with anything less than a /19  in
level3 land aren't going to succeed.

http://v-authoring.ip-plus.net/documents/BIS_TI_Router_Filter_Policy_EN.pdf

ip prefix-list martians seq 8000 permit 8.0.0.0/7 le 19
[etc]

Not so much of a problem in v4 but as you saw for yourself, you risk not
seeing prefixes at all if you try this.

-- 
Suresh Ramasubramanian (ops.lists () gmail com)