Configuring Loop Detection of ACs in a VPLS Network

You can configure loop detect on the AC interfaces of the PE to avoid broadcast storm in the VPLS network.

Applicable Environment

When a CE device accesses the PE devices through redundant attachment circuit (AC) links and when multiple Pseudo Wires (PWs) exist in a VPLS network, a loop may be formed in the network to lead to the broadcast storm. In this case, you need to configure Ethernet loop detection for the VPLS network. In this manner, you can avoid the broadcast storm by blocking the AC links or PWs when a loop occurs.

A router enabled with the loop detect function periodically sends specially constructed loop detect packets. If a routing loop exists on a network, the loop detect packets will be looped back to the router, and the router can then determine that a routing loop has occurred. A malicious attacker can trick a loop-detect-enabled router into believing that a routing loop has occurred, by sending loop detect packet head getting using Sniffer back to the router. It is recommended that you disable the loop detect function on properly operating routers. If you need the loop detect function to detect link connectivity during the site deployment stage, disable this function after this stage.

Pre-configuration Tasks

Before configuring Ethernet loop detection in a VPLS network, complete the following task:

Deploying VPLS on the network to ensure interworking between CE devices

Enabling Loop Detection Globally: Before enabling loop detect on an interface, you must enable loop detect in the system view.

Configuring Loop Detection: You can configure loop detect and block priorities in the interface view.

(Optional) Configuring the VLAN Range for Loop Detection Packets Sent by a Sub-interface for VLAN Tag Termination: Specify the VLAN range for the loop detection packets sent by a sub-interface for dot1q or QinQ VLAN tag termination. This prevents a PE from sending detection packets with the VLAN IDs of all ranges, thus avoiding unnecessary CPU consumption.

Verifying the Configuration: After configuring successfully, you can check information about the loop detect status and loop detect blocking of each interface.