This paper describes the architecture, use-case, and evaluation of a software-defined interconnect. Interconnects at Internet Exchange Points (IXPs) today comprise a layer-2 data-plane and BGP control-plane. We architect, implement, and deploy an SDN-based IXP using ONOS that provides equivalent functionality, while additionally supporting better ARP hygiene and enhanced traffic telemetry. Our system also provides private Internet peering, such as between an enterprise and a cloud provider. We demonstrate a novel use-case enabled by our system, wherein an enterprise can dynamically and transparently switch between public and private peering to access cloud services at appropriate quality and cost points. Evaluation of our solution with real traffic demonstrates that it enables enterprises to manage cloud connect costs flexibly without compromising quality, opening the door to innovative solutions not possible before.