isabled spanning tree, which is on by default, to demonstrate the power of a broadcast storm. Both ports are trunks. There are various devices on other ports on the switches, which cre- ate normal broadcasts (such as ARP and DHCP broadcasts). There is nothing unusual about this network, aside from spanning tree being disabled. F0/14 F0/14 F0/15 F0/15 Switch A Switch B Figure 8-2. Simple layer-2 loop Broadcast Storms Interface F0/15 has already been configured and is operating properly. The output from the show interface fo/15 command shows the input and output rates to be very low (both are around 1,000 bits per second and 2-3 packets per second): 3550-IOS# sho int f0/15 FastEthernet0/15 is up, line protocol is up (connected) Hardware is Fast Ethernet, address is 000f.8f5c.5a0f (bia 000f.8f5c.5a0f) MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec, reliability 255/255, txload 1/255, rxload 1/255 Encapsulation ARPA, loopback not set Keepalive set (10 sec) Full-duplex, 100Mb/s, media type is 10/100BaseTX input flow-control is off, output flow-control is unsupported ARP type: ARPA, ARP Timeout 04:00:00 Last input 00:00:10, output 00:00:00, output hang never Last clearing of "show interface" counters never Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0 Queueing strategy: fifo Output queue: 0/40 (size/max) 5 minute input rate 1000 bits/sec, 2 packets/sec 5 minute output rate 1000 bits/sec, 3 packets/sec 5778444 packets input, 427859448 bytes, 0 no buffer Received 5707586 broadcasts (0 multicast) 0 runts, 0 giants, 0 throttles input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored watchdog, 5707585 multicast, 0 pause input 0 input packets with dribble condition detected 2597516 packets output, 213866427 bytes, 0 underruns A useful tool when troubleshooting a broadcast storm is the show processes cpu history command. This command displays an ASCII histogram of the CPU utilization over the past 72 hours. It produces three graphs: CPU percent per second (last 60 seconds) CPU percent per minute (last 60 minut