MAC_BYTE_MASK
fdb->mac[0] = (reg[0] >> MAC_BYTE_0) & MAC_BYTE_MASK;
fdb->mac[1] = (reg[0] >> MAC_BYTE_1) & MAC_BYTE_MASK;
fdb->mac[2] = (reg[0] >> MAC_BYTE_2) & MAC_BYTE_MASK;
fdb->mac[3] = (reg[0] >> MAC_BYTE_3) & MAC_BYTE_MASK;
fdb->mac[4] = (reg[1] >> MAC_BYTE_4) & MAC_BYTE_MASK;
fdb->mac[5] = (reg[1] >> MAC_BYTE_5) & MAC_BYTE_MASK;