In this paper, we describe a distributed network operating system that runs on merchant silicon based switches. Multiple switches can form a fabric for orchestration and state sharing purposes independent of the network topology. Each switch in a fabric shares its state with other switches over TCP/IP and keeps a global view of virtual ports along with topology to make individual switching, forwarding and encapsulation decisions. This allows the distributed switch OS to track Virtual Machines as they migrate and dynamically orchestrate VXLAN overlays without needing software overlays in servers. Since the Switch OS offloads encapsulation/decapsulation for VXLAN to the switch ASIC, there is no performance penalty. Categories and Subject Descriptors C.2.4 [Computer-Communication Networks]: Network Operating Systems General Terms Performance, Design, Experimentation Keywords VXLAN, Overlay, Distributed Network OS, Netvisor.