[H3C]loopback-detection global enable vlan all //全局开启环路检测，并对所有的VLAN生效
[H3C]loopback-detection interval-time 250 //配置环路检测的时间间隔为250秒
[H3C]int gi 1/0/1
[H3C-GigabitEthernet1/0/1]loopback-detection enable vlan all //接口开启环路检测，并对所有的VLAN生效
[H3C-GigabitEthernet1/0/1]loopback-detection action shutdown //当检测到环路时，环路检测会将此端口关闭
查看环路检测的显示信息：
[H3C]dis loopback-detection
Loopback detection is enabled. //环路检测已开启
Loopback detection interval is 250 second(s). //环路检测的时间间隔为250秒
No loopback is detected. //目前没有检测到环路
