Using ELSM with Layer 2 Control Protocols

You can use ELSM with Layer 2 control protocols such as STP, ESRP, EAPS, and so on to improve the recovery of Layer 2 loops in the network.

ELSM detects remote link failures if the established link is through a Layer 2 transport cloud and the ELSM endpoints traverse the Layer 2 cloud in a point-to-point fashion, as shown in the following figure.

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ELSM Through a Layer 2 Cloud
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A sudden failure of the switch CPU may cause the hardware to continue forwarding traffic. For example, ESRP may select a second device for forwarding traffic thereby creating a Layer 2 loop in the network. If you configure ELSM and the CPU fails, ELSM closes the connection to the faulty device to prevent a loop.