Figure 1 shows a four port switch with four PCs attached one to each port. The PCs are named A, B, C, and D. The abbreviated MAC addresses are 00-0A, 00-0B, 00-0C, and 00-0D. The switch MAC address table is also shown. The MAC table includes port and MAC address for A. The switch received a frame from D and entered the port number and MAC address for D. In Figure 2, the switch forwards the frame out the port associated with A. In Figure 3, A sends another frame to D and the switch only forwards the frame out the port associated with D.