一、实验拓扑：
二、实验命令：
1、基本部署：
IOU1(config)#int range e1/0 - 1
IOU1(config-if-range)#no shutdown
IOU1(config-if-range)#switchport trunk encapsulation dot1q
IOU1(config-if-range)#switchport mode trunk
IOU2(config)#int range e1/0 - 1 IOU2(config-if-range)#no shutdown IOU2(config-if-range)#switchport trunk encapsulation dot1q IOU2(config-if-range)#switchport mode trunk
IOU3(config)#int range e1/0 - 1 IOU3(config-if-range)#no shutdown IOU3(config-if-range)#switchport trunk encapsulation dot1q IOU3(config-if-range)#switchport mode trunk
IOU3(config)#int e1/2 IOU3(config-if)#no shutdown IOU3(config-if)#switchport mode access
2、重点命令： IOU3(config)#int e1/2 IOU3(config-if)#no shutdown IOU3(config-if)#spanning-tree guard root IOU3(config-if)# *Apr 26 06:19:34.814: %SPANTREE-2-ROOTGUARD_CONFIG_CHANGE: Root guard enabled on port Ethernet1/2
IOU3#show spanning-tree vlan 1 Et0/0 Desg FWD 100 128.1 Shr Et0/1 Desg FWD 100 128.2 Shr Et0/2 Desg FWD 100 128.3 Shr Et0/3 Desg FWD 100 128.4 Shr Et1/0 Altn BLK 100 128.5 Shr Et1/1 Root FWD 100 128.6 Shr Et1/2 Desg FWD 100 128.7 Shr
接着在Hacker上做： Hacker(config)#spanning-tree vlan 1 priority 0 IOU3上提示： *Apr 26 06:23:14.796: %SPANTREE-2-ROOTGUARD_BLOCK: Root guard blocking port Ethernet1/2 on VLAN0001.
结果验证： IOU3#show spanning-tree vlan 1 VLAN0001 Interface Role Sts Cost Prio.Nbr Type Et0/0 Desg FWD 100 128.1 Shr Et0/1 Desg FWD 100 128.2 Shr Et0/2 Desg FWD 100 128.3 Shr Et0/3 Desg FWD 100 128.4 Shr Et1/0 Altn BLK 100 128.5 Shr Et1/1 Root FWD 100 128.6 Shr Et1/2 Desg BKN*100 128.7 Shr *ROOT_Inc
