Overview Loopback Detection

In the Ethernet, if the destination of some packet fails to be recognized, they will be flooded in a VLAN. If a loop exists in the network, the packets circulate and multiply without limit, and finally they will use up the bandwidth. Then, the network fails to provide normal communication.

There are two types of loops, loop between different Ethernet interfaces of a device, and loop on one Ethernet interface of a device. The two types of loops can be detected through loopback detection.

After the loopback detection function is enabled, the Ethernet interface sends loopback detection packets with an interval to check whether a loop exists in the network. When the Ethernet interface receives the loopback detection packet sent by the local device, it determines that a loop exists in the network. Then, the Ethernet interface is disabled to prevent the local loop from affecting the entire network.