Localizing traffic using BGP

Well, the most specific prefix wins in the forwarding
selection process, but I won't make any comments on
"best current practice" since "best" is somewhat
relative to the idea of max-aggregation ....but
this reference might help:

G. Huston
Request for Comments: 3221
Commentary on Inter-Domain Routing in the Internet


5.4 Lack of Common Operational Practices

   There is considerable evidence of a lack of uniformity of operational
   practices within the inter-domain routing space. This includes the
   use and setting of prefix filters, the use and setting of route
   damping parameters and level of verification undertaken on BGP
   advertisements by both the advertiser and the recipient. There is
   some extent of 'noise' in the routing table where advertisements
   appear to be propagated well beyond their intended domain of
   applicability, and also where withdrawals and advertisements are not
   being adequately damped close to the origin of the route flap. This
   diversity of operating practices also extends to policies of
   accepting advertisements that are more specific advertisements of
   existing provider blocks.


- ferg