Examples of the present disclosure provide a method of migrating a virtual machine. In response to receiving information of a newly added port, a first controller within a software defined network may search for a matching destination Internet protocol address within a first neighbor relationship table when an IP address contained in the information of the newly added port is taken as a source IP address. The first controller may send flow tables relating to the matching destination IP address to a destination virtual switching device of a migrated virtual machine, and update flow tables stored in virtual switching devices managed by the first controller. The first controller may send a migration success message including the information of the newly added port to a second controller, to enable the second controller to update flow tables stored in virtual switching devices managed by the second controller.