Abstract: A method in which a node of an Ethernet ring network flushes a filtering database includes operating a timer for delaying flushing of the filtering database when a topology of the ring network is changed, and flushing the filtering database when the timer is terminated. A method in which a node of an Ethernet ring network flushes a filtering database includes flushing the filtering database after receiving a protection switching frame that requests flushing of the filtering database, and forwarding a data frame in a queue state at a node and then forwarding the protection switching frame to an adjacent node. A method in which a node of an Ethernet ring network flushes a filtering database includes flushing the filtering database after receiving a protection switching frame that requests flushing of the filtering database, and deleting a data frame in a queue state at the node.