table does not cause the other to become stale. When the ARP cache changes, only the adjacency table changes, SO aging or invalidation of the forwarding table is not required. Interrupt Context Switching CEF supports load balancing over equal-cost paths, as you'll see in the next section. Load balancing at the switching level is far superior to load balancing by routing pro- tocols, as routing protocols operate at a much higher level. The latest versions of IOS incorporate CEF switching into routing protocol load balancing, SO this has become less of an issue. Configuring and Managing Switching Paths Configuring switching paths is done both globally and at the interface level, allowing you the flexibility of configuring different switching paths on each interface. For ex- ample, you may want to disable CEF on an interface to see whether it's causing problems. Process Switching To force a router to use process switching, turn off all other switching methods. Here, I'm showing the performance of a Cisco 2621XM router with about 600k of traffic running over serial interface s0/1: R1#sho int s0/1 I include minute 5 minute input rate 630000 bits/sec, 391 packets/sec 5 minute output rate 627000 bits/sec, 391 packets/sec The normal switching method for this interface on this router is CEF. To see which switching path is running on interface s0/1, use the show ip interface s0/1 include switching command: R1#sho ip interface s0/1 include switching IP fast switching is enabled IP fast switching on the same interface is enabled IP Flow switching is disabled IP CEF switching is enabled IP CEF Fast switching turbo vector IP multicast fast switching is enabled IP multicast distributed fast switching is disabled Notice that fast switching and CEF are both enabled. CEF will try to switch the packet first. If CEF cannot switch the packet, it will punt the packet to the next best available switching path-fast switching. If fast switching cannot process the packet, the router will process-switch the packet. If all the other switchi