MAD 检测机制

可以使用bfd mad，这个需要两台设备单独连根线做，起一个vlan接口。

[DeviceA] interface vlan-interface 3

[DeviceA-Vlan-interface3] mad bfd enable

[DeviceA-Vlan-interface3] mad ip address 192.168.2.1 24 member 1

[DeviceA-Vlan-interface3] mad ip address 192.168.2.2 24 member 2

把连线的接口加入这个vlan，关闭stp。

如果有上联二层聚合链路的话，可以借用这个聚合链路做lacp mad，配置较简单，只需要在聚合接口下：

[DeviceA] interface bridge-aggregation 2

[DeviceA-Bridge-Aggregation2] link-aggregation mode dynamic

[DeviceA-Bridge-Aggregation2] mad enable

 You need to assign a domain ID (range: 0-4294967295)

 [Current domain is: 0]:

 The assigned  domain ID is: 0

 Info: MAD LACP only enable on dynamic aggregation interface.

[DeviceA-Bridge-Aggregation2] quit