A system and method of reducing the input and output pins used to interface a fast serial port Ethernet processing system using multiplexing. Using the system of the present invention, four pins can allow a plurality of Ethernet communication paths to be connected to a single processor on a substrate. These four connections include a clocking input as well as a strobe signal which coordinates the multiplexing and identifies the time period for a predetermined source. The physical layer and the processor are each provided with a multiplexor which is controlled by the strobe to select the network to be coupled at any given time. The multiplexor includes a counter which is incremented by the clocking input and reset by the strobe signal.