Embodiments disclose a method for acquiring, by a switch deployed in a software defined network (SDN), an exact flow entry, where the SDN network includes an SDN controller and multiple SDN switches, the SDN controller being configured to communicate with each SDN switch in an inband communication manner. The method includes establishing, by a first SDN switch, a reliable connection to the SDN controller, and sending a first control message based on a packet corresponding to a protocol for the reliable connection. Path information of the first SDN switch is added to the control message. Each SDN switch that receives the first control message adds path information of each SDN switch to the first control message, so that the SDN controller is provided with an entire path, so as to deliver a flow table to the first SDN switch.