Command rejected: An interface whose trunk encapsulation is "Auto" can not be configured to "trunk" mode.

  问题症状:

  Switch(config-if)#switchport mode trunk

  Command rejected: An interface whose trunk encapsulation is "Auto" can not be configured to "trunk" mode.

  解决方法:

  Switch(config-if)#switchport trunk encapsulation dot1q

  Switch(config-if)#switchport mode trunk

  先配置封装,再设置trunk