Date: Tue, 23 Sep 1997 10:45:19 -0400 From: "Randall S. Benn" <rbenn@clark.net>
I think you'll find that your router's CPU will be happier if you just dump the 1918 networks to the bit bucket on your border routers with a static route via interface Null0:
ip route 10.0.0.0 255.0.0.0 null0 ip route 127.0.0.0 255.0.0.0 null0 etc.
Considering resource utilization on the router, it is cheaper to do a routing table look-up than it is to do ACLs. Also, when you're doing outbound filtering on the router, you have to do a routing table lookup first before you can do outbound filtering. Save a step and just do the routing table lookup.
I don't think so. The static routes will require processing every packet destined for the 10.0.0.0/8 and 127.0.0.0/8 nets, but you will still have the bad route. The CPU will have to deal with any traffic for 10.0.0.0/8 and any interior routers will forward packets since you have a route. On the other hand, a filter on the BGP session will block the route from being accepted and only require CPU action once...when it is announced. You have no route to these nets and can't propagate the routes since you don't have them. Andrew clearly has the correct approach. -- R. Kevin Oberman, Network Engineer Energy Sciences Network (ESnet) Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab) E-mail: oberman@es.net Phone: +1 510 486-8634