The present invention provides a method of limiting the frequency of floods within a data network, the floods arising as a data frame is routed to an unknown destination, the method comprising the steps of: receiving on an ingress port a data frame intended for a destination station and containing a MAC address of that station; checking the destination MAC address with the contents of a MAC table; and thereby determining whether the data frame is to be routed, discarded or flooded to all ports except the ingress port; and respectively routing, discarding or flooding the data frame to all ports except the ingress port. The present invention further provides a method of populating a MAC table within an Ethernet network with entries relating a MAC station address to a port to which it is connected, the method comprising the steps of: receiving on an ingress port a data frame intended for a destination station and containing a MAC address of that station; checking the destination MAC address with the contents of a MAC table; and thereby determining whether the destination MAC address and ingress port are to be written to the MAC table and, if so writing the destination MAC address and ingress port to the MAC table; and flooding the data frame to all ports except the ingress port.