Overview of Layer 2 Loop Detection

Definition

Layer 2 loop detection is a security mechanism used to detect loops on a Layer 2 network. When a Layer 2 loop occurs, a large number of packets will be repeatedly sent to a router's CPU. The traffic burst overloads the CPU, causing normal protocol packets to fail to be sent to the CPU. As a result, normal services will be interrupted. Layer 2 loop detection determines whether a loop has occurred based on information about packets sent to the CPU. After detecting a loop, a router will take the configured responsive action. For example, the system may send a trap to the network management system (NMS) or shut down the interface where the loop has occurred.

Purpose

If Layer 2 loop detection is enabled, the system can rapidly locate the interface where a loop has occurred and send a trap or shut down the interface. This function minimizes service loss caused by Layer 2 loops.

Benefits

Layer 2 loop detection offers the following benefits:

• Rapidly locates the interface where a loop occurs, improving the loop locating efficiency.
• Sends a trap to the NMS after an existing or potential Layer 2 loop is detected so that effective measures can be taken to minimize service loss and prevent major network faults.
• Shuts down the interface where a loop occurs, reducing the adverse impact on the device.