A service provider has a Resilient Ethernet Protocol ring running as a metro backbone between its locations in one city. A customer wants to connect one site with one box redundant to the Resilient Et

Enabling STP only at the SP side does not address the loop potential introduced by the customer's dual connections, leaving the customer side unprotected.

STP at the customer side only could function but is not correct because REP does not interoperate cleanly with STP and Flex Links is the purpose-built solution for a single-box dual-uplink scenario.

Flex Links at the SP side only does not help because the SP ring already uses REP for loop prevention and adding Flex Links on the SP side does not address the loop created by the customer's two connections.

Flex Links configured on the customer device manages the two uplinks to different SP locations by keeping one active and one in hot-standby mode, preventing any loop from forming without requiring changes to the SP side. The REP ring already handles loop prevention within the service provider network, so only the customer side needs an additional redundancy mechanism. Flex Links is purpose-built for this exact scenario - a single device with two uplinks to the same upstream network.

EtherChannel bundles parallel links between the same two endpoints into a single logical link and cannot aggregate links that connect to two different SP devices.

Running STP on both sides creates conflicts with REP, which is designed to replace STP in ring topologies and does not coexist cleanly with it.

Flex Links at both sides is unnecessary because the SP ring already has REP managing its loop prevention, and adding Flex Links on the SP side would interfere with REP operation.