ng paths are turned off, the router must process-switch all packets. To disable all interrupt context switching paths, use the interface command no ip route-cache: R1(config-if)#no ip route-cache (config-if)# ^Z R1# sho ip interface s0/1 include switching 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 44222223333322222000005555566666444444444444444444444444 ************************ CPU% per second (last 60 seconds) The router was running at an average of 4 percent CPU utilization with CEF running. When I disabled all route caching, the router reverted to process switching for all pack- ets. 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: 40% PID Runtime( (ms) Invoked uSecs TTY 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% 0 Check heaps 0.00% 0.00% 0.00% Chunk Manager 12488 328220 0.00% 0.00% 0.00% 0 Load Meter 0.00% 0.00% 0.00% 0 Pool Manager 0 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 ALARM TRIGGER SC 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 here), you need to ask yoursel