A method for obtaining a port path and an apparatus to improve a network capacity, where the method includes receiving, by a controller, a request message from a first server, where the request message requests port path information, and the port path information includes a port that a logical link from the first server to a second server passes through, obtaining, by the controller, a first absolute port path (APP) and a second APP according to network topology information, where the first APP includes a port that a logical link from a root node to the first server passes through, and the second APP includes a port that a logical link from the root node to the second server passes through, obtaining, by the controller, the port path information according to the first APP and the second APP, and sending the port path information to the first server.