ation for the past minute explains why. The histogram shows that for the last 25 seconds, CPU utilization has been at 99 percent. The trouble started 40 seconds ago, which is when I enabled the second trunk: 3550-IOS#sho proc cpu hist 9999999999999999999999999333339999966666 199999999999999999999999999999999993333311111 ***** ***** ***** CPU% per second (last 60 seconds) CPU utilization rocketed to 99 percent within seconds of the loop being created. The switch is expending most of its processing power forwarding broadcasts through the loop. As a result, all other processes start to suffer. Using Telnet or SSH to administer the switch is almost impossible at this point. Even the console is beginning to show signs of sluggishness. Within five minutes, the two links are at 50 percent utilization. They are also sending and receiving in excess of 70,000 packets per second: 3550-IOS#sho int fo/15 FastEtherneto/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 143/255, rxload 143/255 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 00:00:00, 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 56185000 bits/sec, 71160 packets/sec 5 minute output rate 56277000 bits/sec, 70608 packets/sec 48383882 packets input, 112738864 bytes, 0 no buffer Received 48311185 broadcasts (o multicast) 0 runts, 0 giants, 0 throttles 0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored 0 watchdog, 36608855 multicast, 0 pause input Broadcast Storms 0 input packets with dribble condition detected 45107032 packets output, 4212355164 bytes, 356 underruns 0 output errors