R4上设置
R4>en
R4#conf t
R4(config)#no ip routing 去掉路由功能
R4(config)#vlan 10
R4(config-vlan)#vlan 20
R4(config-vlan)#inter f1/1 划分VLAN
R4(config-if)#switchport access vlan 10
R4(config-if)#inter fa1/2
R4(config-if)#switchport access vlan 20
R4(config)#interface range f1/3 -4 设置成中继端口
R4(config-if-range)#switchport mode trunk
R4(config-if-range)#switchport trunk encapsulation dot1q
R4(config-if-range)#ex
R2配置
R2>en
R2#conf t
R2(config)#no ip routing
R2(config)#vlan 10
R2(config-vlan)#vlan 20
R2(config-vlan)#end
R2(config)#interface range f1/1 -2
R2(config-if-range)#switchport mode trunk
R2(config-if-range)#switchport trunk encapsulation dot1q
R2(config-if-range)#ex
R2(config)#spanning-tree vlan 10 root primary 生成树根优先级
VLAN 10 bridge priority set to 8192
VLAN 10 bridge max aging time unchanged at 20
VLAN 10 bridge hello time unchanged at 2
VLAN 10 bridge forward delay unchanged at 15
R2(config)#spanning-tree vlan 20 root secondary
VLAN 20 bridge priority set to 16384
VLAN 20 bridge max aging time unchanged at 20
VLAN 20 bridge hello time unchanged at 2
VLAN 20 bridge forward delay unchanged at 15