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IP Routing Primer by Robert Wright

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Process Switching Versus Fast Switching

The method chosen for packet forwarding is dependent on the type of switching the router is performing for IP datagrams. This book was written using Cisco 2500s running IOS version 11.1. Cisco 2500s running 11.1 only have the following two switching methods available:

  • Process switching (performing packet-by-packet load balancing)

  • Fast switching (performing destination-by-destination load balancing)

Process switching utilizes the CPU for looking up the next hop in the routing table for every packet that needs to be forwarded.

Fast switching, which uses a route cache of the destination IP address and the next hop IP address, is less CPU intensive than process switching. The first packet to any host is always ...

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