te 2741000 bits/sec, 4587 packets/sec Now I start to get warning messages on the console. The EIGRP neighbors are bouncing: 1wod: %DUAL 5 -NBRCHANGE - IP-EIGRP (0) 55: Neighbor 10.55.1.10 (FastEthernet0/13) is down: holding time expire Broadcast Storms 1wod: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 55: Neighbor 10.55.1.10 (FastEthernet0/13) is up: new adjacency 1wod: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 55: Neighbor 10.55.10.3 (Vlan10) is down: retry limit exceeded 1wod: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 55: Neighbor 10.55.10.3 (Vlan10) is up: new adjacency A quick look at the CPU utilization 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 19999999999999999999999999333339999966666 999999999999999999999999999999999993333311111 ***** ***** ***** ********** 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 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 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 Chapter 8: Sp