t time period on the graph. For example, according to the preceding graph, CPU utilization was normally 0 percent, but increased to 1 percent 5 seconds ago and to 3 percent 20 seconds ago. When the values exceed 10 percent, you'll see visual peaks in the graph itself. This switch is a 3550 and has routing protocol neighbors (EIGRP, in this case), SO it's an important device that is providing Layer-3 functionality: 3550-IOS#sho ip eigrp neighbors IP-EIGRP neighbors for process 55 H Address Interface Hold Uptime Seq Type (sec) 10.55.1.10 Fa0/13 14 00:25:30 10.55.10.3 13 1wod Now I'll turn up interface F0/14 as a trunk: 3550-I0S(config)#int f0/14 3550-I0S(config-if)# switchport 3550-I0S(config-if)# switchport trunk encapsulation dot1q 3550-I0S(config-if)# switchport mode trunk There are now two trunks connecting Switch A and Switch B. Remember that I've disabled spanning tree. Mere seconds after I converted F0/14 to a trunk, the input and output rates on F0/15 have shot up from 1,000 bits per second and 2-3 packets per second to 815,000 bits per second and 1,561 packets per second: 3550-IOS#sho int f0/15 I include minute 5 minute input rate 815000 bits/sec, 1565 packets/sec 5 minute output rate 812000 bits/sec, 1561 packets/sec Ten seconds later, the input and output have more than doubled to 2.7 Mbps and over 4,500 packets per second: 3550 IOS#sho int f0/15 I include minute 5 minute input rate 2744000 bits/sec, 4591 packets/sec 5 minute output rate 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 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 Chapter 8: Spanning Tree A quick look at the CPU utiliz