North American Network Operators Group
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Re: Packets from net 10 (no, not the lyrics)

  • From: Nick Hilliard
  • Date: Tue Sep 23 11:30:06 1997 
> 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:

Access-lists like this can also be used for filtering incoming BGP updates.
Bill et al. are referring to this rather than to inbound packet filtering.
The rest of the configuration goes something along the lines of:

router bgp xxxx
 neighbor x.y.z.w distribute-list 100 in

If you're using default-free routing, this will prevent the prefixes from
appearing in your routing table, and the networks will be unreachable.  The
routing entries will also not be propagated any further than necessary.

Nick