Packets from net 10 (no, not the lyrics)

Kenneth E. Gray kegray at cisco.com
Tue Sep 23 17:45:28 UTC 1997


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 at 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 at es.net			Phone: +1 510 486-8634
>
>
Ken Gray                                                 ||        ||
ISP Systems Engineer                                     ||        ||
Reston, Virginia   USA                                  ||||      ||||
tel: +1.703.397.5942                             ..:||||||:..:||||||:..
e-mail: kegray at cisco.com                           c i s c o S y s t e m s
fax: +1.703.397.5999




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