tching IP fast switching is disabled Chapter 15: Switching Algorithms in Cisco Routers IP fast switching on the same interface is disabled IP Flow switching is disabled IP CEF switching is disabled IP Fast switching turbo vector IP multicast fast switching is disabled IP multicast distributed fast switching is disabled I've done this for all interfaces on the router. Now let's look at the CPU utilization on the router with the command show processes cpu history: R1# sho proc cpu hist 44444444444444444444444411111 4444222223333322222000005555566666444444444444444444444444 CPU% per second (last 60 seconds) The router was running at an average of 4 percent CPU utilization with CEF run- ning. When I disabled all route caching, the router reverted to process switching for all packets. For just 600k of traffic, the router is now using 40 percent of its CPU cycles to forward the packets. When a router is process switching most of its IP packets, the top process will always be ip_input. You can verify this by executing the command show processes cpu sorted: R1#sho proc cpu sort CPU utilization for five seconds: 48%/20%; one minute: 44%; five minutes: PID Runtime(ms) Invoked uSecs Process 177614152 132817658 26.60% 24.06% 21.94% 0 IP Input 60540 20255 1.47% 0.22% 0.05% 0 Exec 1496508 210836 0.16% 0.06% 0.05% Check heaps 0.00% 0.00% 0.00% Chunk Manager 12488 328220 0.00% 0.00% 0.00% Load Meter 0.00% 0.00% 0.00% Pool Manager 0.00% 0.00% 0.00% 0 Timers 0.00% 0.00% 0.00% 0 Serial Backgroun 12108 327897 0.00% 0.00% 0.00% 0 ARM TRIGGER This is a good troubleshooting step if you have a router or multilayer switch that is running slowly. If you see ip_input taking up the majority of available CPU time (as shown above), you need to ask yourself why the router is process switching. Check your config and look for problems. Configuring and Managing Switching Paths Packets that are malformed can cause a router to process switch. I've seen Metropolitan Area Ethernet carrier equipment muck up Ethernet packets just enough that the router