Re: Packets from net 10 (no, not the lyrics)

["Kenneth E. Gray" <kegray () cisco com>]

And that would be process switching to Null0, I believe.

At 08:22 AM 9/23/97 -0700, Kevin Oberman wrote:
> > 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
Ken Gray                                                 ||        ||
ISP Systems Engineer                                     ||        ||
Reston, Virginia   USA                                  ||||      ||||
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e-mail: kegray () cisco com                           c i s c o S y s t e m s
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