Cisco交换机端口设置快速转发

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这个是用于接入口的，一个正常的交换接口从down到up要经过:Down,listening,learning,fowarding几个状态，一共耗时为30秒，从而决定此端口是blocking还是fowarding的，也是交换机的防止环路的机制。但是对于直接接入PC这样的终端设备的接口就没有必要经过这几步了，也就是从down直接进入fowarding的状态。

基本的配置方法：
Sw1(config)#spanning-tree portfast default （所有接口启用）全局下用
一般用在接入层的交换机上。

Sw1(config-if)#spanning-tree portfast �0�2接口下单独启用

Sw1(config-if)#spanning-tree portfast disable (某个口禁用，通常是连接另一台交换机的口）