The disclosure provides a link discovery method and an apparatus. The method includes: sending, by a control plane device, a first message to a plurality of forwarding plane devices in a network to which the control plane device belongs, where the first message is used to instruct each forwarding plane device receiving the first message to send a topology discovery packet at all available ports of the forwarding plane device; receiving, by the control plane device, second messages respectively sent by the plurality of forwarding plane devices, where each of the second messages is generated, according to a first topology discovery packet received at a second port, by a second forwarding plane device sending the second message, and determining, by the control plane device, topology connections between the plurality of forwarding plane devices according to the second messages sent by the plurality of forwarding plane devices.