forwarding
        database
    The switch maintains a
        database of all MAC address received on all of its ports and uses this information to decide
        whether a frame should be forwarded or filtered. Each FDB entry consists of the MAC address
        of the sending device, an identifier for the port on which the frame was received, and an
        identifier for the 
VLAN (Virtual LAN) to which the device belongs. Frames
        destined for devices that are not currently in the FDB are flooded to all members of the
        VLAN. For some types of entries, you configure the time it takes for the specific entry to
        age out of the FDB.