A switch receives a first packet, where the first packet includes a source media access control MAC address. The switch obtains a first flapping count corresponding to the source MAC address. The switch determines, based on the first flapping count, whether a loop failure occurs in a network in which the switch is located. When the loop failure occurs in the network in which the switch is located, the switch obtains a flapping port set corresponding to the source MAC address. The switch determines a primary port in the plurality of ports, where the primary port is a port that must be suppressed. The switch enables a flooding suppression function on the primary port, where the flooding suppression function is used to suppress forwarding of a received flooding packet by the primary port.