[c-nsp] Filtering /24s

[Justin M. Streiner]

On Wed, 15 Mar 2006, Greg Boehnlein wrote:

> 	We are looking at some strategies to reduce the load on our core
> routers by filtering all routes that are /24 or smaller. The number of /24
> routes that have propogated in the recent couple of years seems enormous
> to me, and we are starting to hit the limits of the RSP-2 cards in our
> 7500s. Short of chucking the Cisco gear and replacing w/ something that
> can handle a larger table, it seems reasonable to me that we could
> probably reduce the total number of routes significantly if we just
> dropped all the /24s on the floor and let our upstreams handle the routing
> for us.

You could do that if:
1) Your upstreams send you a default plus whatever routes you take from 
them.  Otherwise you end up with the possibility of having reachability 
holes.
2) You're not providing full BGP feeds to any of your downstream 
customers, unless your customers are OK with this and you feed them a 
default route in addition to whatever other routes you feed them.

jms