思科文档对loopback detect errdisable 解析:
A loopback error occurs when the keepalive packet is looped back to the port that sent the keepalive. The switch sends keepalives out all the interfaces by default. A device can loop the packets back to the source interface, which usually occurs because there is a logical loop in the network that the spanning tree has not blocked. The source interface receives the keepalive packet that it sent out, and the switch disables the interface (errdisable).
原因就是链路发现环路,交换机自动将端口进入err状态。
active:
排查链路是什么原因导致环路.一般是链路接线错误或者上联设备有环路导致的。
恢复方法:
确认环路原因后,端口shutdown/no shutdown 就可以恢复。