A method for implementing a software-defined network (SDN) includes receiving, by an SDN controller, virtual network information sent by a cloud computing platform, where the virtual network information includes a correspondence between information about a virtual machine (VM) and information about a server running the VM. The method also includes acquiring, by the SDN controller, physical network information, where the physical network information includes a correspondence between information about a top-of-rack (TOR) switch and the information about the server. Additionally, the method includes acquiring, by the SDN controller, a correspondence between the information about the VM and the information about the TOR switch according to the virtual network information and the physical network information.