Drawback: It is technically challenging to create an automate system to regionalize and create appropriate filter lists.
I always did enjoy a challenge. It's really pretty trivial up on the whiteboard. My model includes BGP confederations to define regions. In the absence of enough IP Addresses to divide your allocations by confederate AS, I am fairly sure the use of communities could be used to hack the distribution of more specifics into conforming the way you want. This is all from memory. I haven't revisted this model much since I developed my first one late last year. Maybe they're some new knobs which make it even easier. Dave -- Dave Siegel Sr. Network Engineer, RTD Systems & Networking (520)623-9663 x130 Network Consultant -- Regional/National NSPs dsiegel@rtd.com User Tracking & Acctg -- "Written by an ISP, http://www.rtd.com/~dsiegel/ for an ISP."