A method for building scalable Ethernet switch network and huge Ethernet switch is provided. The switch network is composed of a plurality of tiers of Ethernet switches forming a fat-tree topology. The bottommost tier connects to the end-stations. All switches except those in the top tier are typical IEEE802.1Q switches configured purposefully such that all packets from the end-stations are forwarded upstream to the top tier and are tagged with ingress port information. The top-tier switches possess a novel learning and forwarding capability such that a received packet is forwarded downstream to the destination end-station through one of a plurality of possible paths selected by a load balancing algorithm. The method can also be applied to build an Ethernet switch of a large number of ports.