Embodiments of the present invention disclose a method for acquiring, by an SDN switch, an exact flow entry, applied to an SDN network, where the SDN network includes an SDN controller and multiple SDN switches, the SDN controller communicates with each SDN switch in an inband communication manner, and the method includes: first establishing, by a first SDN switch, a reliable connection to the SDN controller; then, sending a first control message based on a packet corresponding to a protocol for the reliable connection; adding path information of the first SDN switch to the control message; and subsequently, also adding, by each SDN switch that receives the first control message, path information of each SDN switch to the first control message, so that finally, the SDN controller knows an entire path, so as to deliver a flow table to the first SDN switch.