2.1 Legacy Media Types
2.1.4 Unicast frames

In a LAN, stations use the Layer 2 MAC address in a frame to identify the source and destination. When Station 1 transmits to Station 2 in the Figure, Station 1 generates a frame that includes the Station 2 MAC address (00-60-08-93-AB-12) for the destination and the Station 1 address (00-60-08-93-DB-C1) for the source. This is a unicast frame. Because the LAN is a shared media, all stations on the network receive a copy of the frame. Only Station 2 performs any processing on the frame, however all stations compare the destination MAC address with their own MAC address. If they do not match, the interface module of the station discards (ignores) the frame. This prevents the packet from consuming CPU cycles within the device. Station 2, however, sees a match and sends the packet to the CPU for further analysis. The CPU examines the network protocol information and the intended application and decides whether to drop or use the packet.