Switch(config-if-range)#switchport mode trunk
Command rejected: An interface whose trunk encapsulation is "Auto" can not be configured to "trunk" mode.
說明是trunk幹道封裝出錯,可使用如下命令即可
Switch(config-if-range)#switchport trunk encapsulation dot1q
Switch(config-if-range)#switchport mode trunk
Switch(config-if-range)#switchport trunk permit vlan all (每次配置trunk模式時這條命令一定要用,要不然有些交換機只默認vlan1可以穿過)