Usage Scenario
To ensure traffic proper transmission, run the detect-active-link enable command on a PE interface connecting to CE1 to enable interface status monitoring on the PE, so that when the interface is Down, the Eth-Trunk interface that shares the same VLAN with the interface will send a Flush packet to instruct the peer device to update its ARP entries.
Prerequisites
The interface on which the detect-active-link enable command is to be run must be a Layer 2 interface. If the interface is a Layer 3 interface, run the portswitch command to switch the Layer 3 interface to a Layer 2 interface.
Precautions
The detect-active-link enable command monitors the status of a Layer 2 interface based on the interface's traffic statistics. To help obtain the real-time traffic statistics, run the set flow-stat interval interval command to set the interval at which traffic statistics are collected to a small value (10s is the lower threshold).
By default, the interval at which traffic statistics are collected is 5 minutes. On the network, if an interface connecting a PE to CE1 alternates between Up and Down, traffic statistics on the interface cannot be updated in time. As a result, the Eth-Trunk interface that shares the same VLAN with the interface cannot promptly be aware of the interface status changes and may incorrectly send or send fewer Flush packets than expected.