Disclosed is a method for determining a transmission path of a router system, in which a forwarding table of the router system is managed with a dualized address system including an absolute address indicating a physical port and a relative address indicating the place of the absolute address. Only the absolute address in a relative forwarding table can be changed without changing the relative address when traffic congestion occurs on a certain port of the router system or when load-balancing is needed, so that the router can actively cope with a real-time change of a destination address.