End-to-end multipathing through network having switching devices compatible with different protocols

A first cluster includes first switching devices that are compatible with a software-defined networking (SDN) protocol. A second cluster includes second switching devices within or partially within overlapping the first cluster. Each second switching device is compatible with a protocol for an open systems interconnection (OSI) model layer. The first switching devices include one or more border switching devices located at a boundary between the first cluster and the second cluster. Each border switching device is also compatible with the protocol for the OSI model layer. The first switching devices effect first multipathing through the network except through the second cluster, and the second switching devices effect second multipathing just through the second cluster of the network. As such, the first switching devices and the second switching devices together effect end-to-end multipathing through both the first cluster and the second cluster of the network.