diff --git a/.gitignore b/.gitignore
index 84b3f80..f57123a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -91,3 +91,5 @@ iOSInjectionProject/
 
 __MACOSX
 .DS_Store
+.zhistory
+
diff --git a/Base.lproj/MainMenu.xib b/Base.lproj/MainMenu.xib
index 15abda1..c680f3c 100644
--- a/Base.lproj/MainMenu.xib
+++ b/Base.lproj/MainMenu.xib
@@ -1,8 +1,8 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<document type="com.apple.InterfaceBuilder3.Cocoa.XIB" version="3.0" toolsVersion="17701" targetRuntime="MacOSX.Cocoa" propertyAccessControl="none" useAutolayout="YES">
+<document type="com.apple.InterfaceBuilder3.Cocoa.XIB" version="3.0" toolsVersion="18122" targetRuntime="MacOSX.Cocoa" propertyAccessControl="none" useAutolayout="YES">
     <dependencies>
         <deployment identifier="macosx"/>
-        <plugIn identifier="com.apple.InterfaceBuilder.CocoaPlugin" version="17701"/>
+        <plugIn identifier="com.apple.InterfaceBuilder.CocoaPlugin" version="18122"/>
         <capability name="documents saved in the Xcode 8 format" minToolsVersion="8.0"/>
     </dependencies>
     <objects>
@@ -67,9 +67,19 @@
                 <menuItem title="File" id="656">
                     <menu key="submenu" title="File" id="657">
                         <items>
-                            <menuItem title="Export CSV" keyEquivalent="e" id="668">
+                            <menuItem title="Export Subnets/Hosts" keyEquivalent="e" id="668">
                                 <connections>
-                                    <action selector="exportCSV:" target="b7w-M5-ti7" id="Ks9-gQ-HYU"/>
+                                    <action selector="exportSubnetsHosts:" target="b7w-M5-ti7" id="EHT-lN-ksr"/>
+                                </connections>
+                            </menuItem>
+                            <menuItem title="Export FLSM" keyEquivalent="e" id="xmj-b6-ggW">
+                                <connections>
+                                    <action selector="exportFLSM:" target="b7w-M5-ti7" id="uJ1-dH-jxD"/>
+                                </connections>
+                            </menuItem>
+                            <menuItem title="Export VLSM" keyEquivalent="e" id="XVa-5e-1dG">
+                                <connections>
+                                    <action selector="exportVLSM:" target="b7w-M5-ti7" id="oYt-CR-eL0"/>
                                 </connections>
                             </menuItem>
                             <menuItem title="Export Clipboard" keyEquivalent="b" id="ceZ-iQ-E9j">
@@ -150,6 +160,65 @@
             </items>
             <point key="canvasLocation" x="-49" y="-225"/>
         </menu>
+        <customObject id="420" customClass="NSFontManager"/>
+        <customObject id="b7w-M5-ti7" userLabel="SubnetCalcAppDelegate" customClass="SubnetCalcAppDelegate" customModule="SubnetCalc" customModuleProvider="target">
+            <connections>
+                <outlet property="NSApp" destination="-2" id="wQ1-cQ-1kg"/>
+                <outlet property="addrField" destination="614" id="TxW-DB-fIi"/>
+                <outlet property="bitsOnSlide" destination="710" id="N5K-tl-7ZU"/>
+                <outlet property="classBinaryMap" destination="cg2-6d-5fs" id="KmO-au-Z39"/>
+                <outlet property="classBitMap" destination="Okj-gg-NHb" id="pzE-Be-9mI"/>
+                <outlet property="classHexaMap" destination="bWR-Nt-3oP" id="1an-r6-OxK"/>
+                <outlet property="classType" destination="t0E-pd-tOK" id="3UE-66-0jK"/>
+                <outlet property="darkModeMenu" destination="yys-xA-LTX" id="778-vc-QOQ"/>
+                <outlet property="dotted" destination="LRz-jt-Y3U" id="hWi-oq-xTX"/>
+                <outlet property="exportButton" destination="737" id="FRk-lP-Tdk"/>
+                <outlet property="ipv6Address" destination="cip-g7-vbK" id="HO2-rt-DiG"/>
+                <outlet property="ipv6Arpa" destination="g3E-7f-7pH" id="gO5-Tw-HKx"/>
+                <outlet property="ipv6Compact" destination="vhs-ST-g2o" id="8Fa-9k-k4g"/>
+                <outlet property="ipv6Decimal" destination="aVz-uC-cal" id="Pq4-GB-qm7"/>
+                <outlet property="ipv6HexaID" destination="zUG-9L-Vpv" id="Zvj-I6-5HB"/>
+                <outlet property="ipv6Network" destination="aub-Bq-s74" id="A3V-kl-4xp"/>
+                <outlet property="ipv6Range" destination="tIz-TW-giA" id="3GA-Yj-Crr"/>
+                <outlet property="ipv6SubnetsCombo" destination="6Gb-gW-s1t" id="Obf-Aa-cEO"/>
+                <outlet property="ipv6Type" destination="kjI-Hn-X8U" id="Ar6-02-rTL"/>
+                <outlet property="ipv6maskBitsCombo" destination="DK7-a5-M3j" id="ck7-KR-MoI"/>
+                <outlet property="ipv6maxHostsCombo" destination="q7N-nd-gHk" id="8F3-ex-3DJ"/>
+                <outlet property="ipv6to4Address" destination="tpf-Ay-mfP" id="7bP-fz-Ra4"/>
+                <outlet property="ipv6to4Box" destination="wya-GI-9e3" id="Ver-Z8-ddF"/>
+                <outlet property="maskBitsCombo" destination="569" id="QLr-to-MNE"/>
+                <outlet property="maskBitsFLSMCombo" destination="gL9-R0-Mm4" id="PgH-Df-RS7"/>
+                <outlet property="maskBitsVLSMCombo" destination="73t-4C-ntV" id="mem-om-BbM"/>
+                <outlet property="maxHostsBySubnetCombo" destination="573" id="gGc-XF-9uv"/>
+                <outlet property="maxHostsBySubnetFLSM" destination="bzk-zA-yUc" id="YfO-Uo-mod"/>
+                <outlet property="maxHostsFLSM" destination="6wQ-m8-CJC" id="kbX-xO-1Kr"/>
+                <outlet property="maxSubnetsCombo" destination="571" id="gn7-9F-KtD"/>
+                <outlet property="maxSubnetsFLSM" destination="ElZ-gK-5iz" id="eO2-Ex-JGw"/>
+                <outlet property="requiredHostsVLSM" destination="Yko-qH-e9b" id="V3t-aT-oI4"/>
+                <outlet property="slideFLSM" destination="VOQ-hO-Xwn" id="ugI-Ti-p5A"/>
+                <outlet property="subnetBitsCombo" destination="567" id="6OG-Je-O6u"/>
+                <outlet property="subnetBitsSlide" destination="708" id="sqB-Ih-CjP"/>
+                <outlet property="subnetBroadcast" destination="579" id="LUN-Gy-Me6"/>
+                <outlet property="subnetHostAddrRange" destination="575" id="zmE-hW-8Tq"/>
+                <outlet property="subnetId" destination="577" id="Ult-L5-U9a"/>
+                <outlet property="subnetMaskCombo" destination="565" id="fo8-IZ-74L"/>
+                <outlet property="subnetNameVLSM" destination="wFc-9W-Hbl" id="CqZ-mT-1av"/>
+                <outlet property="subnetsHostsView" destination="586" id="t0i-M1-zXx"/>
+                <outlet property="supernetAddrRange" destination="612" id="oxM-Ko-MTW"/>
+                <outlet property="supernetMaskBitsCombo" destination="602" id="pgy-eF-NAM"/>
+                <outlet property="supernetMaskCombo" destination="604" id="XHV-NL-8kc"/>
+                <outlet property="supernetMaxAddr" destination="606" id="MJZ-X2-yN8"/>
+                <outlet property="supernetMaxCombo" destination="608" id="cQU-yh-ktN"/>
+                <outlet property="supernetMaxSubnetsCombo" destination="EVx-dV-vmg" id="8RC-fU-8J9"/>
+                <outlet property="supernetRoute" destination="610" id="dM3-ms-Vew"/>
+                <outlet property="tabView" destination="533" id="nCF-Ri-pad"/>
+                <outlet property="tabViewClassLess" destination="706" id="kgC-bS-1bz"/>
+                <outlet property="viewFLSM" destination="zYs-mh-V7e" id="6t8-tY-HoL"/>
+                <outlet property="viewVLSM" destination="Xp5-Sj-frC" id="TmV-dj-nMq"/>
+                <outlet property="wildcard" destination="QkZ-rA-ck3" id="5k7-qX-sXw"/>
+                <outlet property="window" destination="371" id="RZ0-ET-tAB"/>
+            </connections>
+        </customObject>
         <window title="SubnetCalc" allowsToolTipsWhenApplicationIsInactive="NO" autorecalculatesKeyViewLoop="NO" releasedWhenClosed="NO" animationBehavior="default" id="371">
             <windowStyleMask key="styleMask" titled="YES" closable="YES" miniaturizable="YES" resizable="YES"/>
             <rect key="contentRect" x="0.0" y="0.0" width="670" height="694"/>
@@ -157,7 +226,7 @@
             <value key="minSize" type="size" width="670" height="694"/>
             <view key="contentView" id="372">
                 <rect key="frame" x="0.0" y="0.0" width="670" height="694"/>
-                <autoresizingMask key="autoresizingMask"/>
+                <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
                 <subviews>
                     <tabView fixedFrame="YES" translatesAutoresizingMaskIntoConstraints="NO" id="533">
                         <rect key="frame" x="13" y="2" width="644" height="648"/>
@@ -472,7 +541,7 @@
                                                 <rect key="frame" x="1" y="1" width="567" height="485"/>
                                                 <autoresizingMask key="autoresizingMask"/>
                                                 <subviews>
-                                                    <tableView verticalHuggingPriority="750" allowsExpansionToolTips="YES" columnSelection="YES" multipleSelection="NO" autosaveColumns="NO" headerView="583" id="586">
+                                                    <tableView identifier="subnetsTabView" verticalHuggingPriority="750" allowsExpansionToolTips="YES" columnSelection="YES" multipleSelection="NO" autosaveColumns="NO" headerView="583" id="586">
                                                         <rect key="frame" x="0.0" y="0.0" width="567" height="462"/>
                                                         <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
                                                         <size key="intercellSpacing" width="3" height="2"/>
@@ -752,6 +821,378 @@
                                     </subviews>
                                 </view>
                             </tabViewItem>
+                            <tabViewItem label="FLSM" identifier="" id="V7w-X8-cub">
+                                <view key="view" id="dhF-QV-G4r">
+                                    <rect key="frame" x="10" y="33" width="624" height="602"/>
+                                    <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
+                                    <subviews>
+                                        <scrollView identifier="subnetsFLSMscroll" fixedFrame="YES" horizontalLineScroll="19" horizontalPageScroll="10" verticalLineScroll="19" verticalPageScroll="10" usesPredominantAxisScrolling="NO" translatesAutoresizingMaskIntoConstraints="NO" id="Cmc-Ha-Hfl">
+                                            <rect key="frame" x="20" y="17" width="584" height="502"/>
+                                            <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
+                                            <clipView key="contentView" id="rby-ox-fjA">
+                                                <rect key="frame" x="1" y="1" width="567" height="485"/>
+                                                <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
+                                                <subviews>
+                                                    <tableView identifier="tabViewFLSM" verticalHuggingPriority="750" allowsExpansionToolTips="YES" columnSelection="YES" multipleSelection="NO" autosaveColumns="NO" headerView="ELH-v1-zWW" id="zYs-mh-V7e">
+                                                        <rect key="frame" x="0.0" y="0.0" width="567" height="457"/>
+                                                        <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
+                                                        <size key="intercellSpacing" width="3" height="2"/>
+                                                        <color key="backgroundColor" name="controlBackgroundColor" catalog="System" colorSpace="catalog"/>
+                                                        <color key="gridColor" name="gridColor" catalog="System" colorSpace="catalog"/>
+                                                        <tableColumns>
+                                                            <tableColumn identifier="numFLSMCol" editable="NO" width="40" minWidth="40" maxWidth="1000" id="vIl-uT-fGb">
+                                                                <tableHeaderCell key="headerCell" lineBreakMode="truncatingTail" borderStyle="border" alignment="left" title="#">
+                                                                    <color key="textColor" name="headerTextColor" catalog="System" colorSpace="catalog"/>
+                                                                    <color key="backgroundColor" white="0.33333298560000002" alpha="1" colorSpace="calibratedWhite"/>
+                                                                </tableHeaderCell>
+                                                                <textFieldCell key="dataCell" scrollable="YES" lineBreakMode="clipping" selectable="YES" editable="YES" alignment="left" id="FCm-3A-vjD">
+                                                                    <font key="font" metaFont="system"/>
+                                                                    <color key="textColor" name="controlTextColor" catalog="System" colorSpace="catalog"/>
+                                                                    <color key="backgroundColor" white="1" alpha="1" colorSpace="calibratedWhite"/>
+                                                                </textFieldCell>
+                                                                <tableColumnResizingMask key="resizingMask" resizeWithTable="YES" userResizable="YES"/>
+                                                            </tableColumn>
+                                                            <tableColumn identifier="subnetFLSMCol" editable="NO" width="120.5" minWidth="40" maxWidth="1000" id="lJf-c5-yfh">
+                                                                <tableHeaderCell key="headerCell" lineBreakMode="truncatingTail" borderStyle="border" alignment="left" title="Subnet ID">
+                                                                    <color key="textColor" name="headerTextColor" catalog="System" colorSpace="catalog"/>
+                                                                    <color key="backgroundColor" white="0.33333298560000002" alpha="1" colorSpace="calibratedWhite"/>
+                                                                </tableHeaderCell>
+                                                                <textFieldCell key="dataCell" scrollable="YES" lineBreakMode="clipping" selectable="YES" editable="YES" alignment="left" id="6gZ-d1-ce0">
+                                                                    <font key="font" metaFont="system"/>
+                                                                    <color key="textColor" name="controlTextColor" catalog="System" colorSpace="catalog"/>
+                                                                    <color key="backgroundColor" white="1" alpha="1" colorSpace="calibratedWhite"/>
+                                                                </textFieldCell>
+                                                                <tableColumnResizingMask key="resizingMask" resizeWithTable="YES" userResizable="YES"/>
+                                                            </tableColumn>
+                                                            <tableColumn identifier="maskFLSMCol" editable="NO" width="57" minWidth="40" maxWidth="1000" id="3Xy-9o-aBa">
+                                                                <tableHeaderCell key="headerCell" lineBreakMode="truncatingTail" borderStyle="border" alignment="left" title="Mask bits">
+                                                                    <color key="textColor" name="headerTextColor" catalog="System" colorSpace="catalog"/>
+                                                                    <color key="backgroundColor" white="0.33333298560000002" alpha="1" colorSpace="calibratedWhite"/>
+                                                                </tableHeaderCell>
+                                                                <textFieldCell key="dataCell" scrollable="YES" lineBreakMode="clipping" selectable="YES" editable="YES" alignment="left" id="RFi-uc-NaN">
+                                                                    <font key="font" metaFont="system"/>
+                                                                    <color key="textColor" name="controlTextColor" catalog="System" colorSpace="catalog"/>
+                                                                    <color key="backgroundColor" white="1" alpha="1" colorSpace="calibratedWhite"/>
+                                                                </textFieldCell>
+                                                                <tableColumnResizingMask key="resizingMask" resizeWithTable="YES" userResizable="YES"/>
+                                                            </tableColumn>
+                                                            <tableColumn identifier="rangeFLSMCol" editable="NO" width="206.343994140625" minWidth="36.844001770019531" maxWidth="1000" id="E3K-mg-KNd">
+                                                                <tableHeaderCell key="headerCell" lineBreakMode="truncatingTail" borderStyle="border" alignment="left" title="Range">
+                                                                    <color key="textColor" name="headerTextColor" catalog="System" colorSpace="catalog"/>
+                                                                    <color key="backgroundColor" name="headerColor" catalog="System" colorSpace="catalog"/>
+                                                                </tableHeaderCell>
+                                                                <textFieldCell key="dataCell" scrollable="YES" lineBreakMode="clipping" selectable="YES" editable="YES" alignment="left" id="T3y-ql-Fsn">
+                                                                    <font key="font" metaFont="system"/>
+                                                                    <color key="textColor" name="controlTextColor" catalog="System" colorSpace="catalog"/>
+                                                                    <color key="backgroundColor" name="controlBackgroundColor" catalog="System" colorSpace="catalog"/>
+                                                                </textFieldCell>
+                                                                <tableColumnResizingMask key="resizingMask" resizeWithTable="YES" userResizable="YES"/>
+                                                            </tableColumn>
+                                                            <tableColumn identifier="broadcastFLSMCol" editable="NO" width="90.01300048828125" minWidth="60.01300048828125" maxWidth="1000" id="xcO-Ca-qbW">
+                                                                <tableHeaderCell key="headerCell" lineBreakMode="truncatingTail" borderStyle="border" alignment="left" title="Broadcast">
+                                                                    <color key="textColor" name="headerTextColor" catalog="System" colorSpace="catalog"/>
+                                                                    <color key="backgroundColor" name="headerColor" catalog="System" colorSpace="catalog"/>
+                                                                </tableHeaderCell>
+                                                                <textFieldCell key="dataCell" scrollable="YES" lineBreakMode="clipping" selectable="YES" editable="YES" alignment="left" id="JVW-S4-CXR">
+                                                                    <font key="font" metaFont="system"/>
+                                                                    <color key="textColor" name="controlTextColor" catalog="System" colorSpace="catalog"/>
+                                                                    <color key="backgroundColor" name="controlBackgroundColor" catalog="System" colorSpace="catalog"/>
+                                                                </textFieldCell>
+                                                                <tableColumnResizingMask key="resizingMask" resizeWithTable="YES" userResizable="YES"/>
+                                                            </tableColumn>
+                                                        </tableColumns>
+                                                        <connections>
+                                                            <outlet property="dataSource" destination="b7w-M5-ti7" id="EdQ-Lq-X7D"/>
+                                                        </connections>
+                                                    </tableView>
+                                                </subviews>
+                                            </clipView>
+                                            <scroller key="horizontalScroller" verticalHuggingPriority="750" horizontal="YES" id="fdD-Yp-Bwf">
+                                                <rect key="frame" x="1" y="486" width="567" height="15"/>
+                                                <autoresizingMask key="autoresizingMask"/>
+                                            </scroller>
+                                            <scroller key="verticalScroller" verticalHuggingPriority="750" horizontal="NO" id="TXj-7k-bNb">
+                                                <rect key="frame" x="568" y="29" width="15" height="457"/>
+                                                <autoresizingMask key="autoresizingMask"/>
+                                            </scroller>
+                                            <tableHeaderView key="headerView" wantsLayer="YES" id="ELH-v1-zWW">
+                                                <rect key="frame" x="0.0" y="0.0" width="567" height="28"/>
+                                                <autoresizingMask key="autoresizingMask"/>
+                                            </tableHeaderView>
+                                        </scrollView>
+                                        <box fixedFrame="YES" title="Mask Bits" translatesAutoresizingMaskIntoConstraints="NO" id="usV-9x-BJc">
+                                            <rect key="frame" x="17" y="523" width="124" height="68"/>
+                                            <autoresizingMask key="autoresizingMask" widthSizable="YES" flexibleMaxX="YES" flexibleMinY="YES"/>
+                                            <view key="contentView" id="y0J-i9-ub4">
+                                                <rect key="frame" x="3" y="3" width="118" height="48"/>
+                                                <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
+                                                <subviews>
+                                                    <comboBox identifier="maskbitsFLSMcombo" verticalHuggingPriority="750" fixedFrame="YES" textCompletion="NO" translatesAutoresizingMaskIntoConstraints="NO" id="gL9-R0-Mm4">
+                                                        <rect key="frame" x="14" y="10" width="95" height="26"/>
+                                                        <autoresizingMask key="autoresizingMask" widthSizable="YES"/>
+                                                        <comboBoxCell key="cell" scrollable="YES" lineBreakMode="clipping" selectable="YES" editable="YES" sendsActionOnEndEditing="YES" borderStyle="bezel" alignment="left" drawsBackground="YES" completes="NO" numberOfVisibleItems="5" id="d18-y9-zSu">
+                                                            <font key="font" metaFont="system"/>
+                                                            <color key="textColor" name="controlTextColor" catalog="System" colorSpace="catalog"/>
+                                                            <color key="backgroundColor" name="textBackgroundColor" catalog="System" colorSpace="catalog"/>
+                                                        </comboBoxCell>
+                                                        <connections>
+                                                            <action selector="changeMaskBits:" target="b7w-M5-ti7" id="yS3-JS-yoT"/>
+                                                        </connections>
+                                                    </comboBox>
+                                                </subviews>
+                                            </view>
+                                            <font key="titleFont" metaFont="message"/>
+                                        </box>
+                                        <textField horizontalHuggingPriority="251" verticalHuggingPriority="750" fixedFrame="YES" translatesAutoresizingMaskIntoConstraints="NO" id="qoS-Wo-Liq">
+                                            <rect key="frame" x="167" y="575" width="61" height="16"/>
+                                            <autoresizingMask key="autoresizingMask" flexibleMinX="YES" flexibleMaxX="YES" flexibleMinY="YES"/>
+                                            <textFieldCell key="cell" lineBreakMode="clipping" alignment="center" title="Subnets" id="JAL-3f-dln">
+                                                <font key="font" metaFont="system"/>
+                                                <color key="textColor" name="labelColor" catalog="System" colorSpace="catalog"/>
+                                                <color key="backgroundColor" name="textBackgroundColor" catalog="System" colorSpace="catalog"/>
+                                            </textFieldCell>
+                                        </textField>
+                                        <textField horizontalHuggingPriority="251" verticalHuggingPriority="750" fixedFrame="YES" translatesAutoresizingMaskIntoConstraints="NO" id="vtO-S0-3fP">
+                                            <rect key="frame" x="326" y="575" width="98" height="16"/>
+                                            <autoresizingMask key="autoresizingMask" flexibleMinX="YES" flexibleMaxX="YES" flexibleMinY="YES"/>
+                                            <textFieldCell key="cell" lineBreakMode="clipping" alignment="center" title="Hosts / Subnet" id="oeU-Gs-Os2">
+                                                <font key="font" metaFont="system"/>
+                                                <color key="textColor" name="labelColor" catalog="System" colorSpace="catalog"/>
+                                                <color key="backgroundColor" name="textBackgroundColor" catalog="System" colorSpace="catalog"/>
+                                            </textFieldCell>
+                                        </textField>
+                                        <textField horizontalHuggingPriority="251" verticalHuggingPriority="750" fixedFrame="YES" translatesAutoresizingMaskIntoConstraints="NO" id="ANz-ku-T1b">
+                                            <rect key="frame" x="534" y="575" width="72" height="16"/>
+                                            <autoresizingMask key="autoresizingMask" flexibleMinX="YES" flexibleMinY="YES"/>
+                                            <textFieldCell key="cell" lineBreakMode="clipping" alignment="center" title="Max Hosts" id="RKL-vr-0uT">
+                                                <font key="font" metaFont="system"/>
+                                                <color key="textColor" name="labelColor" catalog="System" colorSpace="catalog"/>
+                                                <color key="backgroundColor" name="textBackgroundColor" catalog="System" colorSpace="catalog"/>
+                                            </textFieldCell>
+                                        </textField>
+                                        <textField identifier="subnetsFLSM" horizontalHuggingPriority="251" verticalHuggingPriority="750" fixedFrame="YES" translatesAutoresizingMaskIntoConstraints="NO" id="ElZ-gK-5iz">
+                                            <rect key="frame" x="147" y="551" width="100" height="16"/>
+                                            <autoresizingMask key="autoresizingMask" flexibleMinX="YES" flexibleMaxX="YES" flexibleMinY="YES"/>
+                                            <textFieldCell key="cell" lineBreakMode="truncatingTail" selectable="YES" alignment="center" placeholderString="?" id="ze9-O6-tXc">
+                                                <font key="font" metaFont="systemBold"/>
+                                                <color key="textColor" name="labelColor" catalog="System" colorSpace="catalog"/>
+                                                <color key="backgroundColor" name="textBackgroundColor" catalog="System" colorSpace="catalog"/>
+                                            </textFieldCell>
+                                        </textField>
+                                        <textField identifier="hostsBySubnetFLSM" horizontalHuggingPriority="251" verticalHuggingPriority="750" fixedFrame="YES" translatesAutoresizingMaskIntoConstraints="NO" id="bzk-zA-yUc">
+                                            <rect key="frame" x="316" y="551" width="118" height="16"/>
+                                            <autoresizingMask key="autoresizingMask" flexibleMinX="YES" flexibleMaxX="YES" flexibleMinY="YES"/>
+                                            <textFieldCell key="cell" lineBreakMode="truncatingTail" selectable="YES" alignment="center" placeholderString="?" id="lpb-S3-crC">
+                                                <font key="font" metaFont="systemBold"/>
+                                                <color key="textColor" name="labelColor" catalog="System" colorSpace="catalog"/>
+                                                <color key="backgroundColor" name="textBackgroundColor" catalog="System" colorSpace="catalog"/>
+                                            </textFieldCell>
+                                        </textField>
+                                        <slider verticalHuggingPriority="750" fixedFrame="YES" allowsExpansionToolTips="YES" translatesAutoresizingMaskIntoConstraints="NO" id="VOQ-hO-Xwn">
+                                            <rect key="frame" x="144" y="521" width="462" height="28"/>
+                                            <autoresizingMask key="autoresizingMask" flexibleMinX="YES" widthSizable="YES" flexibleMinY="YES"/>
+                                            <sliderCell key="cell" continuous="YES" state="on" baseWritingDirection="leftToRight" alignment="left" minValue="1" maxValue="32" doubleValue="1" tickMarkPosition="above" allowsTickMarkValuesOnly="YES" sliderType="linear" id="adq-jT-IFL"/>
+                                            <connections>
+                                                <action selector="changeSlideFLSM:" target="b7w-M5-ti7" id="UJT-nh-3X8"/>
+                                            </connections>
+                                        </slider>
+                                        <textField identifier="maxHostsFLSM" horizontalHuggingPriority="251" verticalHuggingPriority="750" fixedFrame="YES" translatesAutoresizingMaskIntoConstraints="NO" id="6wQ-m8-CJC">
+                                            <rect key="frame" x="520" y="551" width="100" height="16"/>
+                                            <autoresizingMask key="autoresizingMask" flexibleMinX="YES" flexibleMinY="YES"/>
+                                            <textFieldCell key="cell" lineBreakMode="clipping" selectable="YES" alignment="center" placeholderString="?" id="gVI-i9-MwQ">
+                                                <font key="font" metaFont="systemBold"/>
+                                                <color key="textColor" name="labelColor" catalog="System" colorSpace="catalog"/>
+                                                <color key="backgroundColor" name="textBackgroundColor" catalog="System" colorSpace="catalog"/>
+                                            </textFieldCell>
+                                        </textField>
+                                    </subviews>
+                                </view>
+                            </tabViewItem>
+                            <tabViewItem label="VLSM" identifier="" id="qlb-eT-hmJ">
+                                <view key="view" id="Azy-9S-Vfg">
+                                    <rect key="frame" x="10" y="33" width="624" height="602"/>
+                                    <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
+                                    <subviews>
+                                        <scrollView identifier="subnetsVLSMscroll" fixedFrame="YES" horizontalLineScroll="19" horizontalPageScroll="10" verticalLineScroll="19" verticalPageScroll="10" usesPredominantAxisScrolling="NO" translatesAutoresizingMaskIntoConstraints="NO" id="MOg-yg-UVT">
+                                            <rect key="frame" x="20" y="17" width="584" height="502"/>
+                                            <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
+                                            <clipView key="contentView" id="Ay9-o5-UH1">
+                                                <rect key="frame" x="1" y="1" width="567" height="485"/>
+                                                <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
+                                                <subviews>
+                                                    <tableView identifier="tabViewVLSM" verticalHuggingPriority="750" allowsExpansionToolTips="YES" columnSelection="YES" multipleSelection="NO" autosaveColumns="NO" headerView="SoM-fw-J5F" id="Xp5-Sj-frC">
+                                                        <rect key="frame" x="0.0" y="0.0" width="579" height="457"/>
+                                                        <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
+                                                        <size key="intercellSpacing" width="3" height="2"/>
+                                                        <color key="backgroundColor" name="controlBackgroundColor" catalog="System" colorSpace="catalog"/>
+                                                        <color key="gridColor" name="gridColor" catalog="System" colorSpace="catalog"/>
+                                                        <tableColumns>
+                                                            <tableColumn identifier="numVLSMCol" editable="NO" width="40" minWidth="40" maxWidth="1000" id="Eu0-7r-yh6">
+                                                                <tableHeaderCell key="headerCell" lineBreakMode="truncatingTail" borderStyle="border" alignment="left" title="#">
+                                                                    <color key="textColor" name="headerTextColor" catalog="System" colorSpace="catalog"/>
+                                                                    <color key="backgroundColor" white="0.33333298560000002" alpha="1" colorSpace="calibratedWhite"/>
+                                                                </tableHeaderCell>
+                                                                <textFieldCell key="dataCell" scrollable="YES" lineBreakMode="clipping" selectable="YES" editable="YES" alignment="left" id="d5P-vM-V9I">
+                                                                    <font key="font" metaFont="system"/>
+                                                                    <color key="textColor" name="controlTextColor" catalog="System" colorSpace="catalog"/>
+                                                                    <color key="backgroundColor" white="1" alpha="1" colorSpace="calibratedWhite"/>
+                                                                </textFieldCell>
+                                                                <tableColumnResizingMask key="resizingMask" resizeWithTable="YES" userResizable="YES"/>
+                                                            </tableColumn>
+                                                            <tableColumn identifier="subnetVLSMCol" editable="NO" width="80.5" minWidth="40" maxWidth="1000" id="FDz-C7-f0L">
+                                                                <tableHeaderCell key="headerCell" lineBreakMode="truncatingTail" borderStyle="border" alignment="left" title="Subnet ID">
+                                                                    <color key="textColor" name="headerTextColor" catalog="System" colorSpace="catalog"/>
+                                                                    <color key="backgroundColor" white="0.33333298560000002" alpha="1" colorSpace="calibratedWhite"/>
+                                                                </tableHeaderCell>
+                                                                <textFieldCell key="dataCell" scrollable="YES" lineBreakMode="clipping" selectable="YES" editable="YES" alignment="left" id="odS-Ro-bRD">
+                                                                    <font key="font" metaFont="system"/>
+                                                                    <color key="textColor" name="controlTextColor" catalog="System" colorSpace="catalog"/>
+                                                                    <color key="backgroundColor" white="1" alpha="1" colorSpace="calibratedWhite"/>
+                                                                </textFieldCell>
+                                                                <tableColumnResizingMask key="resizingMask" resizeWithTable="YES" userResizable="YES"/>
+                                                            </tableColumn>
+                                                            <tableColumn identifier="maskVLSMCol" editable="NO" width="80.5" minWidth="40" maxWidth="1000" id="xmh-O5-nD9">
+                                                                <tableHeaderCell key="headerCell" lineBreakMode="truncatingTail" borderStyle="border" alignment="left" title="Mask bits">
+                                                                    <color key="textColor" name="headerTextColor" catalog="System" colorSpace="catalog"/>
+                                                                    <color key="backgroundColor" white="0.33333298560000002" alpha="1" colorSpace="calibratedWhite"/>
+                                                                </tableHeaderCell>
+                                                                <textFieldCell key="dataCell" scrollable="YES" lineBreakMode="clipping" selectable="YES" editable="YES" alignment="left" id="fs3-23-43q">
+                                                                    <font key="font" metaFont="system"/>
+                                                                    <color key="textColor" name="controlTextColor" catalog="System" colorSpace="catalog"/>
+                                                                    <color key="backgroundColor" white="1" alpha="1" colorSpace="calibratedWhite"/>
+                                                                </textFieldCell>
+                                                                <tableColumnResizingMask key="resizingMask" resizeWithTable="YES" userResizable="YES"/>
+                                                            </tableColumn>
+                                                            <tableColumn identifier="nameVLSMCol" editable="NO" width="203.843994140625" minWidth="36.844001770019531" maxWidth="1000" id="rxF-Te-Q4K">
+                                                                <tableHeaderCell key="headerCell" lineBreakMode="truncatingTail" borderStyle="border" alignment="left" title="Subnet Name">
+                                                                    <color key="textColor" name="headerTextColor" catalog="System" colorSpace="catalog"/>
+                                                                    <color key="backgroundColor" name="headerColor" catalog="System" colorSpace="catalog"/>
+                                                                </tableHeaderCell>
+                                                                <textFieldCell key="dataCell" scrollable="YES" lineBreakMode="clipping" selectable="YES" editable="YES" alignment="left" id="juC-wO-jPv">
+                                                                    <font key="font" metaFont="system"/>
+                                                                    <color key="textColor" name="controlTextColor" catalog="System" colorSpace="catalog"/>
+                                                                    <color key="backgroundColor" name="controlBackgroundColor" catalog="System" colorSpace="catalog"/>
+                                                                </textFieldCell>
+                                                                <tableColumnResizingMask key="resizingMask" resizeWithTable="YES" userResizable="YES"/>
+                                                            </tableColumn>
+                                                            <tableColumn identifier="usedVLSMCol" editable="NO" width="149.51300048828125" minWidth="60.01300048828125" maxWidth="1000" id="DJx-OR-eSI">
+                                                                <tableHeaderCell key="headerCell" lineBreakMode="truncatingTail" borderStyle="border" alignment="left" title="Used">
+                                                                    <color key="textColor" name="headerTextColor" catalog="System" colorSpace="catalog"/>
+                                                                    <color key="backgroundColor" name="headerColor" catalog="System" colorSpace="catalog"/>
+                                                                </tableHeaderCell>
+                                                                <textFieldCell key="dataCell" scrollable="YES" lineBreakMode="clipping" selectable="YES" editable="YES" alignment="left" id="zJ1-IZ-8II">
+                                                                    <font key="font" metaFont="system"/>
+                                                                    <color key="textColor" name="controlTextColor" catalog="System" colorSpace="catalog"/>
+                                                                    <color key="backgroundColor" name="controlBackgroundColor" catalog="System" colorSpace="catalog"/>
+                                                                </textFieldCell>
+                                                                <tableColumnResizingMask key="resizingMask" resizeWithTable="YES" userResizable="YES"/>
+                                                            </tableColumn>
+                                                        </tableColumns>
+                                                        <connections>
+                                                            <outlet property="dataSource" destination="b7w-M5-ti7" id="wKM-A7-jKm"/>
+                                                        </connections>
+                                                    </tableView>
+                                                </subviews>
+                                            </clipView>
+                                            <scroller key="horizontalScroller" verticalHuggingPriority="750" horizontal="YES" id="LGz-mF-ToX">
+                                                <rect key="frame" x="1" y="486" width="567" height="15"/>
+                                                <autoresizingMask key="autoresizingMask"/>
+                                            </scroller>
+                                            <scroller key="verticalScroller" verticalHuggingPriority="750" horizontal="NO" id="m1X-wx-IVe">
+                                                <rect key="frame" x="568" y="29" width="15" height="457"/>
+                                                <autoresizingMask key="autoresizingMask"/>
+                                            </scroller>
+                                            <tableHeaderView key="headerView" wantsLayer="YES" id="SoM-fw-J5F">
+                                                <rect key="frame" x="0.0" y="0.0" width="579" height="28"/>
+                                                <autoresizingMask key="autoresizingMask"/>
+                                            </tableHeaderView>
+                                        </scrollView>
+                                        <box fixedFrame="YES" title="Mask Bits" translatesAutoresizingMaskIntoConstraints="NO" id="GOC-MO-WPQ">
+                                            <rect key="frame" x="17" y="523" width="124" height="68"/>
+                                            <autoresizingMask key="autoresizingMask" widthSizable="YES" flexibleMaxX="YES" flexibleMinY="YES"/>
+                                            <view key="contentView" id="9tk-S3-fBT">
+                                                <rect key="frame" x="3" y="3" width="118" height="48"/>
+                                                <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
+                                                <subviews>
+                                                    <comboBox identifier="maskbitsVLSMcombo" verticalHuggingPriority="750" fixedFrame="YES" textCompletion="NO" translatesAutoresizingMaskIntoConstraints="NO" id="73t-4C-ntV">
+                                                        <rect key="frame" x="14" y="10" width="95" height="26"/>
+                                                        <autoresizingMask key="autoresizingMask" widthSizable="YES"/>
+                                                        <comboBoxCell key="cell" scrollable="YES" lineBreakMode="clipping" selectable="YES" editable="YES" sendsActionOnEndEditing="YES" borderStyle="bezel" alignment="left" drawsBackground="YES" completes="NO" numberOfVisibleItems="5" id="h4B-Xe-Deq">
+                                                            <font key="font" metaFont="system"/>
+                                                            <color key="textColor" name="controlTextColor" catalog="System" colorSpace="catalog"/>
+                                                            <color key="backgroundColor" name="textBackgroundColor" catalog="System" colorSpace="catalog"/>
+                                                        </comboBoxCell>
+                                                        <connections>
+                                                            <action selector="changeMaskBits:" target="b7w-M5-ti7" id="sIB-zT-KeW"/>
+                                                        </connections>
+                                                    </comboBox>
+                                                </subviews>
+                                            </view>
+                                            <font key="titleFont" metaFont="message"/>
+                                        </box>
+                                        <textField verticalHuggingPriority="750" fixedFrame="YES" translatesAutoresizingMaskIntoConstraints="NO" id="Yko-qH-e9b">
+                                            <rect key="frame" x="292" y="557" width="231" height="21"/>
+                                            <autoresizingMask key="autoresizingMask" flexibleMinX="YES" widthSizable="YES" flexibleMinY="YES"/>
+                                            <textFieldCell key="cell" scrollable="YES" lineBreakMode="clipping" selectable="YES" editable="YES" borderStyle="bezel" placeholderString="# Hosts" drawsBackground="YES" id="jXR-8r-mbe">
+                                                <font key="font" metaFont="system"/>
+                                                <color key="textColor" name="controlTextColor" catalog="System" colorSpace="catalog"/>
+                                                <color key="backgroundColor" name="textBackgroundColor" catalog="System" colorSpace="catalog"/>
+                                            </textFieldCell>
+                                            <connections>
+                                                <action selector="addSubnetVLSM:" target="b7w-M5-ti7" id="L97-Po-jeR"/>
+                                            </connections>
+                                        </textField>
+                                        <textField verticalHuggingPriority="750" fixedFrame="YES" translatesAutoresizingMaskIntoConstraints="NO" id="wFc-9W-Hbl">
+                                            <rect key="frame" x="292" y="527" width="231" height="21"/>
+                                            <autoresizingMask key="autoresizingMask" flexibleMinX="YES" widthSizable="YES" flexibleMinY="YES"/>
+                                            <textFieldCell key="cell" scrollable="YES" lineBreakMode="clipping" selectable="YES" editable="YES" borderStyle="bezel" placeholderString="Subnet Name (optional)" drawsBackground="YES" id="Z07-Ng-G9U">
+                                                <font key="font" metaFont="system"/>
+                                                <color key="textColor" name="controlTextColor" catalog="System" colorSpace="catalog"/>
+                                                <color key="backgroundColor" name="textBackgroundColor" catalog="System" colorSpace="catalog"/>
+                                            </textFieldCell>
+                                            <connections>
+                                                <action selector="addSubnetVLSM:" target="b7w-M5-ti7" id="C7v-Yp-FdZ"/>
+                                            </connections>
+                                        </textField>
+                                        <button verticalHuggingPriority="750" fixedFrame="YES" translatesAutoresizingMaskIntoConstraints="NO" id="Mi2-yq-Stu">
+                                            <rect key="frame" x="524" y="521" width="90" height="32"/>
+                                            <autoresizingMask key="autoresizingMask" flexibleMinX="YES" flexibleMinY="YES"/>
+                                            <buttonCell key="cell" type="push" title="Clear" bezelStyle="rounded" alignment="center" borderStyle="border" imageScaling="proportionallyDown" inset="2" id="gih-YH-gK0">
+                                                <behavior key="behavior" pushIn="YES" lightByBackground="YES" lightByGray="YES"/>
+                                                <font key="font" metaFont="system"/>
+                                            </buttonCell>
+                                            <connections>
+                                                <action selector="clearSubnetsVLSM:" target="b7w-M5-ti7" id="vHD-UW-xYx"/>
+                                            </connections>
+                                        </button>
+                                        <button verticalHuggingPriority="750" fixedFrame="YES" translatesAutoresizingMaskIntoConstraints="NO" id="fa0-PM-ymd">
+                                            <rect key="frame" x="524" y="551" width="48" height="32"/>
+                                            <autoresizingMask key="autoresizingMask" flexibleMinX="YES" flexibleMinY="YES"/>
+                                            <buttonCell key="cell" type="push" title="+" bezelStyle="rounded" alignment="center" borderStyle="border" imageScaling="proportionallyDown" inset="2" id="hYg-WK-tJP">
+                                                <behavior key="behavior" pushIn="YES" lightByBackground="YES" lightByGray="YES"/>
+                                                <font key="font" metaFont="system"/>
+                                            </buttonCell>
+                                            <connections>
+                                                <action selector="addSubnetVLSM:" target="b7w-M5-ti7" id="PKD-8O-ZS0"/>
+                                            </connections>
+                                        </button>
+                                        <button verticalHuggingPriority="750" fixedFrame="YES" translatesAutoresizingMaskIntoConstraints="NO" id="u4b-Xm-Cfc">
+                                            <rect key="frame" x="566" y="551" width="48" height="32"/>
+                                            <autoresizingMask key="autoresizingMask" flexibleMinX="YES" flexibleMinY="YES"/>
+                                            <buttonCell key="cell" type="push" title="-" bezelStyle="rounded" alignment="center" borderStyle="border" imageScaling="proportionallyDown" inset="2" id="rOa-NA-psd">
+                                                <behavior key="behavior" pushIn="YES" lightByBackground="YES" lightByGray="YES"/>
+                                                <font key="font" metaFont="system"/>
+                                                <string key="keyEquivalent" base64-UTF8="YES">
+CA
+</string>
+                                            </buttonCell>
+                                            <connections>
+                                                <action selector="deleteSubnetVLSM:" target="b7w-M5-ti7" id="Yjd-nr-Uej"/>
+                                            </connections>
+                                        </button>
+                                    </subviews>
+                                </view>
+                            </tabViewItem>
                             <tabViewItem label="IPv6" identifier="" id="wMi-TX-Blk">
                                 <view key="view" id="fbb-SV-9YD">
                                     <rect key="frame" x="10" y="33" width="624" height="602"/>
@@ -1023,9 +1464,19 @@
                             <menu key="menu" title="OtherViews" id="739">
                                 <items>
                                     <menuItem hidden="YES" id="740"/>
-                                    <menuItem title="Export CSV" id="742">
+                                    <menuItem title="Export Subnets/Hosts" id="742">
+                                        <connections>
+                                            <action selector="exportSubnetsHosts:" target="b7w-M5-ti7" id="207-fy-PIx"/>
+                                        </connections>
+                                    </menuItem>
+                                    <menuItem title="Export FLSM" id="pbN-aM-Sl1">
                                         <connections>
-                                            <action selector="exportCSV:" target="b7w-M5-ti7" id="4Td-Nv-X6s"/>
+                                            <action selector="exportFLSM:" target="b7w-M5-ti7" id="X2n-6Q-aS4"/>
+                                        </connections>
+                                    </menuItem>
+                                    <menuItem title="Export VLSM" id="Tui-fq-nG6">
+                                        <connections>
+                                            <action selector="exportVLSM:" target="b7w-M5-ti7" id="74Q-4L-4K8"/>
                                         </connections>
                                     </menuItem>
                                     <menuItem title="Export Clipboard" id="mB2-aR-3r0">
@@ -1065,54 +1516,5 @@
             </connections>
             <point key="canvasLocation" x="84" y="281"/>
         </window>
-        <customObject id="420" customClass="NSFontManager"/>
-        <customObject id="b7w-M5-ti7" userLabel="SubnetCalcAppDelegate" customClass="SubnetCalcAppDelegate" customModule="SubnetCalc" customModuleProvider="target">
-            <connections>
-                <outlet property="NSApp" destination="-2" id="wQ1-cQ-1kg"/>
-                <outlet property="addrField" destination="614" id="TxW-DB-fIi"/>
-                <outlet property="bitsOnSlide" destination="710" id="N5K-tl-7ZU"/>
-                <outlet property="classBinaryMap" destination="cg2-6d-5fs" id="KmO-au-Z39"/>
-                <outlet property="classBitMap" destination="Okj-gg-NHb" id="pzE-Be-9mI"/>
-                <outlet property="classHexaMap" destination="bWR-Nt-3oP" id="1an-r6-OxK"/>
-                <outlet property="classType" destination="t0E-pd-tOK" id="3UE-66-0jK"/>
-                <outlet property="darkModeMenu" destination="yys-xA-LTX" id="778-vc-QOQ"/>
-                <outlet property="dotted" destination="LRz-jt-Y3U" id="hWi-oq-xTX"/>
-                <outlet property="exportButton" destination="737" id="FRk-lP-Tdk"/>
-                <outlet property="ipv6Address" destination="cip-g7-vbK" id="HO2-rt-DiG"/>
-                <outlet property="ipv6Arpa" destination="g3E-7f-7pH" id="gO5-Tw-HKx"/>
-                <outlet property="ipv6Compact" destination="vhs-ST-g2o" id="8Fa-9k-k4g"/>
-                <outlet property="ipv6Decimal" destination="aVz-uC-cal" id="Pq4-GB-qm7"/>
-                <outlet property="ipv6HexaID" destination="zUG-9L-Vpv" id="Zvj-I6-5HB"/>
-                <outlet property="ipv6Network" destination="aub-Bq-s74" id="A3V-kl-4xp"/>
-                <outlet property="ipv6Range" destination="tIz-TW-giA" id="3GA-Yj-Crr"/>
-                <outlet property="ipv6SubnetsCombo" destination="6Gb-gW-s1t" id="Obf-Aa-cEO"/>
-                <outlet property="ipv6Type" destination="kjI-Hn-X8U" id="Ar6-02-rTL"/>
-                <outlet property="ipv6maskBitsCombo" destination="DK7-a5-M3j" id="ck7-KR-MoI"/>
-                <outlet property="ipv6maxHostsCombo" destination="q7N-nd-gHk" id="8F3-ex-3DJ"/>
-                <outlet property="ipv6to4Address" destination="tpf-Ay-mfP" id="7bP-fz-Ra4"/>
-                <outlet property="ipv6to4Box" destination="wya-GI-9e3" id="Ver-Z8-ddF"/>
-                <outlet property="maskBitsCombo" destination="569" id="QLr-to-MNE"/>
-                <outlet property="maxHostsBySubnetCombo" destination="573" id="gGc-XF-9uv"/>
-                <outlet property="maxSubnetsCombo" destination="571" id="gn7-9F-KtD"/>
-                <outlet property="subnetBitsCombo" destination="567" id="6OG-Je-O6u"/>
-                <outlet property="subnetBitsSlide" destination="708" id="sqB-Ih-CjP"/>
-                <outlet property="subnetBroadcast" destination="579" id="LUN-Gy-Me6"/>
-                <outlet property="subnetHostAddrRange" destination="575" id="zmE-hW-8Tq"/>
-                <outlet property="subnetId" destination="577" id="Ult-L5-U9a"/>
-                <outlet property="subnetMaskCombo" destination="565" id="fo8-IZ-74L"/>
-                <outlet property="subnetsHostsView" destination="586" id="t0i-M1-zXx"/>
-                <outlet property="supernetAddrRange" destination="612" id="oxM-Ko-MTW"/>
-                <outlet property="supernetMaskBitsCombo" destination="602" id="pgy-eF-NAM"/>
-                <outlet property="supernetMaskCombo" destination="604" id="XHV-NL-8kc"/>
-                <outlet property="supernetMaxAddr" destination="606" id="MJZ-X2-yN8"/>
-                <outlet property="supernetMaxCombo" destination="608" id="cQU-yh-ktN"/>
-                <outlet property="supernetMaxSubnetsCombo" destination="EVx-dV-vmg" id="8RC-fU-8J9"/>
-                <outlet property="supernetRoute" destination="610" id="dM3-ms-Vew"/>
-                <outlet property="tabView" destination="533" id="nCF-Ri-pad"/>
-                <outlet property="tabViewClassLess" destination="706" id="kgC-bS-1bz"/>
-                <outlet property="wildcard" destination="QkZ-rA-ck3" id="5k7-qX-sXw"/>
-                <outlet property="window" destination="371" id="RZ0-ET-tAB"/>
-            </connections>
-        </customObject>
     </objects>
 </document>
diff --git a/IPSubnetcalc.swift b/IPSubnetcalc.swift
index c0de9de..160ee0c 100644
--- a/IPSubnetcalc.swift
+++ b/IPSubnetcalc.swift
@@ -502,6 +502,19 @@ class IPSubnetCalc: NSObject {
         return (bitMap)
     }
     
+    // return maskbits and number of max hosts for this mask
+    static func fittingSubnet(hosts: UInt) -> (Int, UInt) {
+        var maxHosts: UInt
+        
+        for index in 1...31 {
+            maxHosts = UInt(truncating: NSDecimalNumber(decimal: pow(2, index))) - 2
+            if (hosts <= maxHosts) {
+                return (32 - index, maxHosts)
+            }
+        }
+        return (0, 0)
+    }
+    
     func displayIPInfo() {
         print("IP Host : " + self.ipv4Address)
         print("Mask bits : \(self.maskBits)")
@@ -548,39 +561,39 @@ class IPSubnetCalc: NSObject {
         
         ip4Hex = ipAddress.components(separatedBy: ":")
         if (ip4Hex == nil) {
-            print("\(ipAddress) invalid")
+            //print("\(ipAddress) invalid")
             return false
         }
         if (ip4Hex!.count != 8) {
-            print("no 8 hex")
+            //print("no 8 hex")
             if (ipAddress.contains("::"))
             {
                 if (ipAddress.components(separatedBy: "::").count > 2) {
-                    print("too many '::'")
+                    //print("too many '::'")
                     return false
                 }
             }
             else {
-                print("IPv6 \(ipAddress) bad format")
+                //print("IPv6 \(ipAddress) bad format")
                 return false
             }
         }
         for index in 0...(ip4Hex!.count - 1) {
             //print("Index : \(index) IPHex : \(ip4Hex[index]) Dec : \(String(UInt16(ip4Hex[index], radix: 16)!, radix: 16))")
             if (ip4Hex![index].count > 4 && ip4Hex![index].count != 0) {
-                print("\(ip4Hex![index]) too large")
+                //print("\(ip4Hex![index]) too large")
                 return false
             }
             hex = UInt16(ip4Hex![index], radix: 16)
             if hex != nil {
                 if (hex! < 0 || hex! > 0xFFFF) {
-                    print("\(hex!) is invalid")
+                    //print("\(hex!) is invalid")
                     return false
                 }
             }
             else {
                 if (ip4Hex![index] != "") {
-                    print("\(ip4Hex![index]) not an integer")
+                    //print("\(ip4Hex![index]) not an integer")
                     return false
                 }
             }
diff --git a/README.md b/README.md
index afa0f02..ef4fb4b 100644
--- a/README.md
+++ b/README.md
@@ -1,14 +1,11 @@
 # SubnetCalc
 Subnet Calculator for MacOS 
 
-What's New in version 2.0:
-- IPv6 support!
-- Address Class D (Multicast) and Class E (Reserved) support
-- 31 and 32 mask bits support
-- New Tab presentation
-- Recoded in Swift
-- Add alerts for bad IP or mask format
-- Fix bugs
+What's New in version 2.1:
+- FLSM (Fixed Length Subnet Mask) support
+- VLSM (Variable Length Subnet Mask) support
+- Export FSLM result in a CSV file
+- Export VSLM result in a CSV file
 
 
 For more information: http://subnetcalc.mulot.org
diff --git a/SubnetCalc-Info.plist b/SubnetCalc-Info.plist
index 27f8f5a..0a089da 100644
--- a/SubnetCalc-Info.plist
+++ b/SubnetCalc-Info.plist
@@ -15,17 +15,17 @@
 	<key>CFBundlePackageType</key>
 	<string>APPL</string>
 	<key>CFBundleShortVersionString</key>
-	<string>2.0</string>
+	<string>2.1</string>
 	<key>CFBundleSignature</key>
 	<string>JMUL</string>
 	<key>CFBundleVersion</key>
-	<string>4</string>
+	<string>$(CURRENT_PROJECT_VERSION)</string>
 	<key>LSApplicationCategoryType</key>
 	<string>public.app-category.utilities</string>
 	<key>LSMinimumSystemVersion</key>
 	<string>${MACOSX_DEPLOYMENT_TARGET}</string>
 	<key>NSHumanReadableCopyright</key>
-	<string>Copyright 2020 Julien Mulot</string>
+	<string>Copyright 2021 Julien Mulot</string>
 	<key>NSMainNibFile</key>
 	<string>MainMenu</string>
 	<key>NSPrincipalClass</key>
diff --git a/SubnetCalc.xcodeproj/project.pbxproj b/SubnetCalc.xcodeproj/project.pbxproj
index 19c1567..3021f2a 100644
--- a/SubnetCalc.xcodeproj/project.pbxproj
+++ b/SubnetCalc.xcodeproj/project.pbxproj
@@ -36,7 +36,7 @@
 		8D1107310486CEB800E47090 /* SubnetCalc-Info.plist */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text.plist.xml; path = "SubnetCalc-Info.plist"; sourceTree = "<group>"; };
 		8D1107320486CEB800E47090 /* SubnetCalc.app */ = {isa = PBXFileReference; explicitFileType = wrapper.application; includeInIndex = 0; path = SubnetCalc.app; sourceTree = BUILT_PRODUCTS_DIR; };
 		945E62EF25658A9500CDC9C7 /* SubnetCalc.xctestplan */ = {isa = PBXFileReference; lastKnownFileType = text; path = SubnetCalc.xctestplan; sourceTree = "<group>"; };
-		945E62F525658DBF00CDC9C7 /* SubnetCalcUITests-Runner.app */ = {isa = PBXFileReference; explicitFileType = wrapper.cfbundle; includeInIndex = 0; path = "SubnetCalcUITests-Runner.app"; sourceTree = BUILT_PRODUCTS_DIR; };
+		945E62F525658DBF00CDC9C7 /* SubnetCalcUITests-Runner.app */ = {isa = PBXFileReference; explicitFileType = wrapper.cfbundle; includeInIndex = 0; name = "SubnetCalcUITests-Runner.app"; path = SubnetCalcUITests.xctest; sourceTree = BUILT_PRODUCTS_DIR; };
 		945E62F925658DBF00CDC9C7 /* Info.plist */ = {isa = PBXFileReference; lastKnownFileType = text.plist.xml; path = Info.plist; sourceTree = "<group>"; };
 		9482A32625765B30008D2C56 /* SubnetCalcUITest.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = SubnetCalcUITest.swift; sourceTree = "<group>"; };
 		949420B712D3C62A00E2F57D /* License.txt */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text; path = License.txt; sourceTree = "<group>"; };
@@ -401,6 +401,7 @@
 				CODE_SIGN_IDENTITY = "Mac Developer";
 				COMBINE_HIDPI_IMAGES = YES;
 				COPY_PHASE_STRIP = NO;
+				CURRENT_PROJECT_VERSION = 7;
 				DEVELOPMENT_TEAM = VNLK894MAE;
 				ENABLE_HARDENED_RUNTIME = YES;
 				GCC_DYNAMIC_NO_PIC = NO;
@@ -428,6 +429,7 @@
 				CODE_SIGN_ENTITLEMENTS = SubnetCalc.entitlements;
 				CODE_SIGN_IDENTITY = "Mac Developer";
 				COMBINE_HIDPI_IMAGES = YES;
+				CURRENT_PROJECT_VERSION = 7;
 				DEBUG_INFORMATION_FORMAT = "dwarf-with-dsym";
 				DEVELOPMENT_TEAM = VNLK894MAE;
 				ENABLE_HARDENED_RUNTIME = YES;
diff --git a/SubnetCalcAppDelegate.swift b/SubnetCalcAppDelegate.swift
index b17de97..e8e9271 100644
--- a/SubnetCalcAppDelegate.swift
+++ b/SubnetCalcAppDelegate.swift
@@ -54,6 +54,16 @@ class SubnetCalcAppDelegate: NSObject, NSApplicationDelegate, NSWindowDelegate,
     @IBOutlet var tabViewClassLess: NSButton!
     @IBOutlet var wildcard: NSButton!
     @IBOutlet var dotted: NSButton!
+    @IBOutlet var maskBitsFLSMCombo: NSComboBox!
+    @IBOutlet var viewFLSM: NSTableView!
+    @IBOutlet var slideFLSM: NSSlider!
+    @IBOutlet var maxSubnetsFLSM: NSTextField!
+    @IBOutlet var maxHostsBySubnetFLSM: NSTextField!
+    @IBOutlet var maxHostsFLSM: NSTextField!
+    @IBOutlet var maskBitsVLSMCombo: NSComboBox!
+    @IBOutlet var requiredHostsVLSM: NSTextField!
+    @IBOutlet var subnetNameVLSM: NSTextField!
+    @IBOutlet var viewVLSM: NSTableView!
     
     //IPv6 UI elements
     @IBOutlet var ipv6Address: NSTextField!
@@ -72,8 +82,9 @@ class SubnetCalcAppDelegate: NSObject, NSApplicationDelegate, NSWindowDelegate,
     
     
     //Private global vars
-    private var savedTabView: [NSTabViewItem]? //ex tab_tabView
     private var ipsc: IPSubnetCalc?
+    private var subnetsVLSM = [(Int, String, String)]()
+    private var globalMaskVLSM: UInt32!
     
     
     //Private IPv4 functions
@@ -122,6 +133,19 @@ class SubnetCalcAppDelegate: NSObject, NSApplicationDelegate, NSWindowDelegate,
         classHexaMap.stringValue = "01.00.00.00"
     }
     
+    private func initFLSMTab() {
+        for bits in (8...32) {
+            maskBitsFLSMCombo.addItem(withObjectValue: String(bits))
+        }
+        slideFLSM.integerValue = 1
+    }
+    
+    private func initVLSMTab() {
+        for bits in (8...32) {
+            maskBitsVLSMCombo.addItem(withObjectValue: String(bits))
+        }
+    }
+    
     private func bitsOnSlidePos()
     {
         var coordLabel = bitsOnSlide.frame
@@ -148,15 +172,6 @@ class SubnetCalcAppDelegate: NSObject, NSApplicationDelegate, NSWindowDelegate,
         else if (c == "D")
         {
             classType.selectItem(at: 3)
-            /*
-             savedTabView = tabView.tabViewItems
-             if (savedTabView != nil)
-             {
-             tabView.removeTabViewItem(savedTabView![1])
-             tabView.removeTabViewItem(savedTabView![2])
-             tabView.removeTabViewItem(savedTabView![3])
-             }
-             */
         }
         else if (c == "E")
         {
@@ -221,6 +236,59 @@ class SubnetCalcAppDelegate: NSObject, NSApplicationDelegate, NSWindowDelegate,
         }
     }
     
+    private func doFLSM()
+    {
+        if (ipsc != nil) {
+            maskBitsFLSMCombo.selectItem(withObjectValue: String(ipsc!.maskBits))
+            if (ipsc!.maskBits <= 29) {
+                slideFLSM.numberOfTickMarks = (30 - ipsc!.maskBits)
+                slideFLSM.maxValue = Double(30 - ipsc!.maskBits)
+                self.maxSubnetsFLSM.stringValue = NSDecimalNumber(decimal: (pow(2, slideFLSM.integerValue))).stringValue
+                self.maxHostsBySubnetFLSM.stringValue = NSDecimalNumber(decimal: (pow(2, (32 - (ipsc!.maskBits + slideFLSM.integerValue)))) - 2).stringValue
+                self.maxHostsFLSM.stringValue = NSDecimalNumber(decimal: ((pow(2, (32 - (ipsc!.maskBits + slideFLSM.integerValue)))) - 2) * (pow(2, slideFLSM.integerValue))).stringValue
+            }
+            else {
+                self.maxSubnetsFLSM.stringValue = ""
+                self.maxHostsBySubnetFLSM.stringValue = ""
+                self.maxHostsFLSM.stringValue = ""
+            }
+            viewFLSM.reloadData()
+        }
+    }
+    
+    private func doVLSM()
+    {
+        if (ipsc != nil) {
+            //print("doVLSM")
+            maskBitsVLSMCombo.selectItem(withObjectValue: String(ipsc!.maskBits))
+            var maskVLSM = ~IPSubnetCalc.numerize(maskbits: ipsc!.maskBits) + 1
+            if (subnetsVLSM.count != 0) {
+                var fitsRequirements = true
+                for index in (0...(subnetsVLSM.count - 1)) {
+                    let maskbits = subnetsVLSM[index].0
+                    //print("Mask VLSM: \(IPSubnetCalc.digitize(ipAddress: maskVLSM)) Maskbits: \(IPSubnetCalc.digitize(ipAddress: ~IPSubnetCalc.numerize(maskbits: maskbits)))")
+                    if (maskVLSM > ~IPSubnetCalc.numerize(maskbits: maskbits)) {
+                        maskVLSM = maskVLSM - (~IPSubnetCalc.numerize(maskbits: maskbits) + 1)
+                        //print("Mask AFTER VLSM: \(IPSubnetCalc.digitize(ipAddress: maskVLSM))")
+                    }
+                    else {
+                        fitsRequirements = false
+                    }
+                }
+                if (fitsRequirements) {
+                    globalMaskVLSM = maskVLSM
+                }
+                else {
+                    myAlert(message: "Mask bits too small", info: "Mask bits doest not suit all VLSM hosts requirements")
+                }
+            }
+            else {
+                globalMaskVLSM = maskVLSM
+            }
+            viewVLSM.reloadData()
+        }
+    }
+    
     private func doCIDR(maskbits: Int? = nil)
     {
         if (ipsc != nil) {
@@ -305,16 +373,13 @@ class SubnetCalcAppDelegate: NSObject, NSApplicationDelegate, NSWindowDelegate,
                 ipsc = IPSubnetCalc(ipAddress: ipaddr, maskbits: Int(ipmask!)!)
             }
             if (ipsc != nil) {
-                if (tabView.numberOfTabViewItems != 4 && savedTabView != nil) {
-                    tabView.addTabViewItem(savedTabView![1])
-                    tabView.addTabViewItem(savedTabView![2])
-                    tabView.addTabViewItem(savedTabView![3])
-                }
                 self.doAddressMap()
                 self.doSubnet()
                 self.doSubnetHost()
                 self.doCIDR()
                 self.doIPv6()
+                self.doFLSM()
+                self.doVLSM()
             }
         }
         else {
@@ -405,15 +470,12 @@ class SubnetCalcAppDelegate: NSObject, NSApplicationDelegate, NSWindowDelegate,
             //print("IP Address: \(ipaddr) mask: \(ipmask)")
             ipsc = IPSubnetCalc(ipv6: ipaddr, maskbits: Int(ipmask!)!)
             if (ipsc != nil) {
-                if (tabView.numberOfTabViewItems != 4 && savedTabView != nil) {
-                    tabView.addTabViewItem(savedTabView![1])
-                    tabView.addTabViewItem(savedTabView![2])
-                    tabView.addTabViewItem(savedTabView![3])
-                }
                 self.doAddressMap()
                 self.doSubnet()
                 self.doSubnetHost()
                 self.doCIDR()
+                self.doFLSM()
+                self.doVLSM()
                 self.doIPv6()
             }
         }
@@ -427,11 +489,6 @@ class SubnetCalcAppDelegate: NSObject, NSApplicationDelegate, NSWindowDelegate,
     //IPv4 UI actions
     @IBAction func changeAddrClassType(_ sender: AnyObject)
     {
-        if (tabView.numberOfTabViewItems != 4 && savedTabView != nil) {
-            tabView.addTabViewItem(savedTabView![1])
-            tabView.addTabViewItem(savedTabView![2])
-            tabView.addTabViewItem(savedTabView![3])
-        }
         if (sender.indexOfSelectedItem() == 0)
         {
             classBitMap.stringValue = "nnnnnnnn.hhhhhhhh.hhhhhhhh.hhhhhhhh"
@@ -452,30 +509,12 @@ class SubnetCalcAppDelegate: NSObject, NSApplicationDelegate, NSWindowDelegate,
         }
         else if (sender.indexOfSelectedItem() == 3)
         {
-            /*
-             savedTabView = tabView.tabViewItems
-             if (savedTabView != nil)
-             {
-             tabView.removeTabViewItem(savedTabView![1])
-             tabView.removeTabViewItem(savedTabView![2])
-             tabView.removeTabViewItem(savedTabView![3])
-             }
-             */
             classBitMap.stringValue = "hhhhhhhh.hhhhhhhh.hhhhhhhh.hhhhhhhh"
             classBinaryMap.stringValue = "11100000.00000000.00000000.00000000"
             classHexaMap.stringValue = "E0.00.00.00"
         }
         else if (sender.indexOfSelectedItem() == 4)
         {
-            /*
-             savedTabView = tabView.tabViewItems
-             if (savedTabView != nil)
-             {
-             tabView.removeTabViewItem(savedTabView![1])
-             tabView.removeTabViewItem(savedTabView![2])
-             tabView.removeTabViewItem(savedTabView![3])
-             }
-             */
             classBitMap.stringValue = "hhhhhhhh.hhhhhhhh.hhhhhhhh.hhhhhhhh"
             classBinaryMap.stringValue = "11110000.00000000.00000000.00000000"
             classHexaMap.stringValue = "F0.00.00.00"
@@ -716,12 +755,22 @@ class SubnetCalcAppDelegate: NSObject, NSApplicationDelegate, NSWindowDelegate,
     func numberOfRows(in tableView: NSTableView) -> Int
     {
         if (ipsc != nil) {
-            if (tabViewClassLess.state == NSControl.StateValue.on) {
-                //print("numberOfRows: Maskbits : \(ipsc!.maskBits) Bits compute: \(ipsc!.maskBits - Constants.NETWORK_BITS_MIN_CLASSLESS) Power: \(NSDecimalNumber(decimal: pow(2, (ipsc!.maskBits - Constants.NETWORK_BITS_MIN_CLASSLESS))))")
-                return Int(truncating: NSDecimalNumber(decimal: pow(2, (ipsc!.maskBits - Constants.NETWORK_BITS_MIN_CLASSLESS))))
+            if (tableView == subnetsHostsView) {
+                if (tabViewClassLess.state == NSControl.StateValue.on) {
+                    //print("numberOfRows: Maskbits : \(ipsc!.maskBits) Bits compute: \(ipsc!.maskBits - Constants.NETWORK_BITS_MIN_CLASSLESS) Power: \(NSDecimalNumber(decimal: pow(2, (ipsc!.maskBits - Constants.NETWORK_BITS_MIN_CLASSLESS))))")
+                    return Int(truncating: NSDecimalNumber(decimal: pow(2, (ipsc!.maskBits - Constants.NETWORK_BITS_MIN_CLASSLESS))))
+                }
+                else {
+                    return (ipsc!.maxSubnets())
+                }
             }
-            else {
-                return (ipsc!.maxSubnets())
+            else if (tableView == viewFLSM) {
+                if (ipsc!.maskBits <= 29) {
+                    return  Int(truncating: NSDecimalNumber(decimal: pow(2, slideFLSM.integerValue)))
+                }
+            }
+            else if (tableView == viewVLSM) {
+                return  (subnetsVLSM.count)
             }
         }
         return 0
@@ -732,21 +781,73 @@ class SubnetCalcAppDelegate: NSObject, NSApplicationDelegate, NSWindowDelegate,
                    row: Int) -> Any?
     {
         if (ipsc != nil) {
-            let ipaddr: UInt32 = (((IPSubnetCalc.numerize(ipAddress: ipsc!.ipv4Address) & ipsc!.classMask()) >> (32 - ipsc!.maskBits)) + UInt32(row)) << (32 - ipsc!.maskBits)
-            let ipsc_tmp = IPSubnetCalc(ipAddress: IPSubnetCalc.digitize(ipAddress: ipaddr), maskbits: ipsc!.maskBits)
-            //print("tableView Row: \(row) IP num : \(ipaddr) IP: \(IPSubnetCalc.digitize(ipAddress: ipaddr)) IP Subnet: \(ipsc_tmp!.subnetId())")
-            if (tableColumn != nil && ipsc_tmp != nil) {
-                if (tableColumn!.identifier.rawValue == "numCol") {
-                    return (row + 1)
-                }
-                else if (tableColumn!.identifier.rawValue == "subnetCol") {
-                    return (ipsc_tmp!.subnetId())
+            //print("Refresh TableView: \(String(describing: tableView.identifier))")
+            if (tableView == subnetsHostsView) {
+                let ipaddr: UInt32 = (((IPSubnetCalc.numerize(ipAddress: ipsc!.ipv4Address) & ipsc!.classMask()) >> (32 - ipsc!.maskBits)) + UInt32(row)) << (32 - ipsc!.maskBits)
+                let ipsc_tmp = IPSubnetCalc(ipAddress: IPSubnetCalc.digitize(ipAddress: ipaddr), maskbits: ipsc!.maskBits)
+                //print("tableView Row: \(row) IP num : \(ipaddr) IP: \(IPSubnetCalc.digitize(ipAddress: ipaddr)) IP Subnet: \(ipsc_tmp!.subnetId())")
+                if (tableColumn != nil && ipsc_tmp != nil) {
+                    if (tableColumn!.identifier.rawValue == "numCol") {
+                        return (row + 1)
+                    }
+                    else if (tableColumn!.identifier.rawValue == "subnetCol") {
+                        return (ipsc_tmp!.subnetId())
+                    }
+                    else if (tableColumn!.identifier.rawValue == "rangeCol") {
+                        return (ipsc_tmp!.subnetRange())
+                    }
+                    else if (tableColumn!.identifier.rawValue == "broadcastCol") {
+                        return (ipsc_tmp!.subnetBroadcast())
+                    }
                 }
-                else if (tableColumn!.identifier.rawValue == "rangeCol") {
-                    return (ipsc_tmp!.subnetRange())
+            }
+            else if (tableView == viewFLSM) {
+                //print("refresh View FLSM")
+                var ipaddr: UInt32 = ((IPSubnetCalc.numerize(ipAddress: ipsc!.ipv4Address) & ipsc!.classMask()) >> (32 - ipsc!.maskBits)) << (32 - ipsc!.maskBits)
+                ipaddr = (ipaddr >> (32 - (ipsc!.maskBits + slideFLSM.integerValue)) + UInt32(row)) << (32 - (ipsc!.maskBits + slideFLSM.integerValue))
+                let ipsc_tmp = IPSubnetCalc(ipAddress: IPSubnetCalc.digitize(ipAddress: ipaddr), maskbits: (ipsc!.maskBits + slideFLSM.integerValue))
+                if (tableColumn != nil && ipsc_tmp != nil) {
+                    if (tableColumn!.identifier.rawValue == "numFLSMCol") {
+                        return (row + 1)
+                    }
+                    else if (tableColumn!.identifier.rawValue == "subnetFLSMCol") {
+                        return (ipsc_tmp!.subnetId())
+                    }
+                    else if (tableColumn!.identifier.rawValue == "maskFLSMCol") {
+                        return (ipsc!.maskBits + slideFLSM.integerValue)
+                    }
+                    else if (tableColumn!.identifier.rawValue == "rangeFLSMCol") {
+                        return (ipsc_tmp!.subnetRange())
+                    }
+                    else if (tableColumn!.identifier.rawValue == "broadcastFLSMCol") {
+                        return (ipsc_tmp!.subnetBroadcast())
+                    }
                 }
-                else if (tableColumn!.identifier.rawValue == "broadcastCol") {
-                    return (ipsc_tmp!.subnetBroadcast())
+            }
+            else if (tableView == viewVLSM) {
+                //print("refresh View VLSM")
+                if (tableColumn != nil) {
+                    if (tableColumn!.identifier.rawValue == "numVLSMCol") {
+                        return (row + 1)
+                    }
+                    else if (tableColumn!.identifier.rawValue == "subnetVLSMCol") {
+                        var subnet = IPSubnetCalc.numerize(ipAddress: ipsc!.subnetId())
+                        if (row > 0) {
+                            for index in (0...(row - 1)) {
+                                subnet = subnet + ~IPSubnetCalc.numerize(maskbits: subnetsVLSM[index].0) + 1
+                            }
+                        }
+                        return (IPSubnetCalc.digitize(ipAddress: subnet))
+                    }
+                    else if (tableColumn!.identifier.rawValue == "maskVLSMCol") {
+                        return (subnetsVLSM[row].0)
+                    }
+                    else if (tableColumn!.identifier.rawValue == "nameVLSMCol") {
+                        return (subnetsVLSM[row].1)
+                    }
+                    else if (tableColumn!.identifier.rawValue == "usedVLSMCol") {
+                        return (subnetsVLSM[row].2)
+                    }
                 }
             }
         }
@@ -778,6 +879,93 @@ class SubnetCalcAppDelegate: NSObject, NSApplicationDelegate, NSWindowDelegate,
         }
     }
     
+    @IBAction func changeSlideFLSM(_ sender: AnyObject)
+    {
+        if (ipsc == nil)
+        {
+            ipsc = IPSubnetCalc(Constants.defaultIP)
+        }
+        if ((ipsc!.maskBits + (sender.intValue as Int)) <= 30)
+        {
+            //print("FLSM Bits: \(sender.intValue as Int)")
+            self.doFLSM()
+        }
+    }
+    
+    @IBAction func addSubnetVLSM(_ sender: AnyObject)
+    {
+        var maskbits: Int
+        var hosts: UInt
+        var used: Int
+        
+        if (ipsc == nil)
+        {
+            ipsc = IPSubnetCalc(Constants.defaultIP)
+        }
+        if (requiredHostsVLSM.integerValue != 0) {
+            //print("VLSM Hosts required: \(requiredHostsVLSM.integerValue)")
+            (maskbits, hosts) = IPSubnetCalc.fittingSubnet(hosts: UInt(requiredHostsVLSM.integerValue))
+            if (maskbits != 0) {
+                used = (requiredHostsVLSM.integerValue * 100) / Int(hosts)
+                //print("VLSM fitting subnet mask: \(maskbits) with \(hosts) max hosts")
+                if (subnetsVLSM.count != 0) {
+                    //print("VLSM subnets NOT empty")
+                    //print("Mask VLSM: \(IPSubnetCalc.digitize(ipAddress: globalMaskVLSM)) Maskbits: \(IPSubnetCalc.digitize(ipAddress: ~IPSubnetCalc.numerize(maskbits: maskbits)))")
+                    if (globalMaskVLSM > ~IPSubnetCalc.numerize(maskbits: maskbits)) {
+                        globalMaskVLSM = globalMaskVLSM - (~IPSubnetCalc.numerize(maskbits: maskbits) + 1)
+                        //print("Mask AFTER VLSM: \(IPSubnetCalc.digitize(ipAddress: globalMaskVLSM))")
+                        if let index = subnetsVLSM.firstIndex(where: { $0.0 > maskbits }) {
+                            subnetsVLSM.insert((maskbits, subnetNameVLSM.stringValue, "\(requiredHostsVLSM.stringValue)/\(hosts) (\(used)%)"), at: index)
+                        }
+                        else {
+                            subnetsVLSM.append((maskbits, subnetNameVLSM.stringValue, "\(requiredHostsVLSM.stringValue)/\(hosts) (\(used)%)"))
+                        }
+                        //subnetsVLSM.append(("dsds", maskbits, subnetNameVLSM.stringValue, "\(requiredHostsVLSM.stringValue)/\(hosts) (\(used)%)"))
+                    }
+                    else {
+                        myAlert(message: "No space for Hosts requirement", info: "\(requiredHostsVLSM.integerValue) hosts require /\(maskbits) Mask bits")
+                    }
+                }
+                else {
+                    //print("VLSM subnets empty")
+                    globalMaskVLSM = ~IPSubnetCalc.numerize(maskbits: ipsc!.maskBits) + 1
+                    //print("Mask VLSM: \(IPSubnetCalc.digitize(ipAddress: globalMaskVLSM)) Maskbits: \(IPSubnetCalc.digitize(ipAddress: ~IPSubnetCalc.numerize(maskbits: maskbits)))")
+                    if (globalMaskVLSM > ~IPSubnetCalc.numerize(maskbits: maskbits)) {
+                        globalMaskVLSM = globalMaskVLSM - (~IPSubnetCalc.numerize(maskbits: maskbits) + 1)
+                        //print("Mask AFTER VLSM: \(IPSubnetCalc.digitize(ipAddress: globalMaskVLSM))")
+                        subnetsVLSM.append((maskbits, subnetNameVLSM.stringValue, "\(requiredHostsVLSM.stringValue)/\(hosts) (\(used)%)"))
+                    }
+                    else {
+                        myAlert(message: "No space for Hosts requirement", info: "\(requiredHostsVLSM.integerValue) hosts require /\(maskbits) Mask bits")
+                    }
+                    
+                }
+                viewVLSM.reloadData()
+            }
+        }
+        else {
+            myAlert(message: "Bad VLSM required Hosts number", info: "\(requiredHostsVLSM.integerValue) is not a number")
+        }
+        requiredHostsVLSM.stringValue = ""
+        subnetNameVLSM.stringValue = ""
+    }
+    
+    @IBAction func deleteSubnetVLSM(_ sender: AnyObject)
+    {
+        if (subnetsVLSM.count != 0) {
+            if (viewVLSM.selectedRow != -1) {
+                //print ("Row : \(viewVLSM.selectedRow)")
+                subnetsVLSM.remove(at: viewVLSM.selectedRow)
+                doVLSM()
+            }
+        }
+    }
+    
+    @IBAction func clearSubnetsVLSM(_ sender: AnyObject) {
+        subnetsVLSM.removeAll()
+        doVLSM()
+    }
+    
     @IBAction func changeTableViewClass(_ sender: AnyObject)
     {
         if (tabViewClassLess.state == NSControl.StateValue.off) {
@@ -870,7 +1058,7 @@ class SubnetCalcAppDelegate: NSObject, NSApplicationDelegate, NSWindowDelegate,
     {
         if (addrField.stringValue.contains(":")) {
             self.doIPv6SubnetCalc()
-            tabView.selectTabViewItem(at: 3)
+            tabView.selectTabViewItem(at: 5)
         }
         else {
             self.doIPSubnetCalc()
@@ -883,7 +1071,7 @@ class SubnetCalcAppDelegate: NSObject, NSApplicationDelegate, NSWindowDelegate,
         self.calc(sender)
     }
     
-    @IBAction func exportCSV(_ sender: AnyObject)
+    @IBAction func exportSubnetsHosts(_ sender: AnyObject)
     {
         if (ipsc != nil) {
             let panel = NSSavePanel()
@@ -922,6 +1110,97 @@ class SubnetCalcAppDelegate: NSObject, NSApplicationDelegate, NSWindowDelegate,
         }
     }
     
+    @IBAction func exportFLSM(_ sender: AnyObject)
+    {
+        if (ipsc != nil) {
+            if (ipsc!.maskBits <= 29) {
+                let panel = NSSavePanel()
+                panel.allowedFileTypes = ["csv"]
+                panel.begin(completionHandler: { (result) in
+                    if (result == NSApplication.ModalResponse.OK && panel.url != nil) {
+                        var fileMgt: FileManager
+                        if #available(OSX 10.14, *) {
+                            fileMgt = FileManager(authorization: NSWorkspace.Authorization())
+                        } else {
+                            // Fallback on earlier versions
+                            fileMgt = FileManager.default
+                        }
+                        fileMgt.createFile(atPath: panel.url!.path, contents: nil, attributes: nil)
+                        //var cvsData = NSMutableData.init(capacity: Constants.BUFFER_LINES)
+                        var cvsData = Data(capacity: Constants.BUFFER_LINES)
+                        let cvsFile = FileHandle(forWritingAtPath: panel.url!.path)
+                        if (cvsFile != nil) {
+                            var cvsStr = "#;Subnet ID;Mask bits;Range;Broadcast\n"
+                            let subnetid: UInt32 = ((IPSubnetCalc.numerize(ipAddress: self.ipsc!.ipv4Address) & self.ipsc!.classMask()) >> (32 - self.ipsc!.maskBits)) << (32 - self.ipsc!.maskBits)
+                            for index in (0...(Int(truncating: NSDecimalNumber(decimal: pow(2, self.slideFLSM.integerValue))) - 1)) {
+                                let ipaddr = (subnetid   >> (32 - (self.ipsc!.maskBits + self.slideFLSM.integerValue)) + UInt32(index)) << (32 - (self.ipsc!.maskBits + self.slideFLSM.integerValue))
+                                let ipsc_tmp = IPSubnetCalc(ipAddress: IPSubnetCalc.digitize(ipAddress: ipaddr), maskbits: (self.ipsc!.maskBits + self.slideFLSM.integerValue))
+                                if (ipsc_tmp != nil) {
+                                    cvsStr.append("\(index + 1);\(ipsc_tmp!.subnetId());\(self.ipsc!.maskBits + self.slideFLSM.integerValue);\(ipsc_tmp!.subnetRange());\(ipsc_tmp!.subnetBroadcast())\n")
+                                }
+                            }
+                            cvsData.append(cvsStr.data(using: String.Encoding.ascii)!)
+                            cvsFile!.write(cvsData)
+                            cvsFile!.synchronizeFile()
+                            cvsFile!.closeFile()
+                        }
+                    }
+                }
+                )
+            }
+            else {
+                myAlert(message: "Cannot not export FLSM Info", info: "Mask bits \(ipsc!.maskBits) > 29")
+            }
+        }
+    }
+    
+    @IBAction func exportVLSM(_ sender: AnyObject)
+    {
+        if (ipsc != nil) {
+            if (subnetsVLSM.count != 0) {
+                let panel = NSSavePanel()
+                panel.allowedFileTypes = ["csv"]
+                panel.begin(completionHandler: { (result) in
+                    if (result == NSApplication.ModalResponse.OK && panel.url != nil) {
+                        var fileMgt: FileManager
+                        if #available(OSX 10.14, *) {
+                            fileMgt = FileManager(authorization: NSWorkspace.Authorization())
+                        } else {
+                            // Fallback on earlier versions
+                            fileMgt = FileManager.default
+                        }
+                        fileMgt.createFile(atPath: panel.url!.path, contents: nil, attributes: nil)
+                        //var cvsData = NSMutableData.init(capacity: Constants.BUFFER_LINES)
+                        var cvsData = Data(capacity: Constants.BUFFER_LINES)
+                        let cvsFile = FileHandle(forWritingAtPath: panel.url!.path)
+                        if (cvsFile != nil) {
+                            var cvsStr = "#;Subnet ID;Mask bits;Subnet Name;Used\n"
+                            let subnetid = IPSubnetCalc.numerize(ipAddress: self.ipsc!.subnetId())
+                            for index in (0...(self.subnetsVLSM.count - 1)) {
+                                var subnet = subnetid
+                                if (index > 0) {
+                                    for index2 in (0...(index - 1)) {
+                                        subnet = subnet + ~IPSubnetCalc.numerize(maskbits: self.subnetsVLSM[index2].0) + 1
+                                    }
+                                }
+                                //print("VLSM: \(index + 1);\(IPSubnetCalc.digitize(ipAddress: subnet));\(self.subnetsVLSM[index].0);\(self.subnetsVLSM[index].1);\(self.subnetsVLSM[index].2)\n")
+                                cvsStr.append("\(index + 1);\(IPSubnetCalc.digitize(ipAddress: subnet));\(self.subnetsVLSM[index].0);\(self.subnetsVLSM[index].1);\(self.subnetsVLSM[index].2)\n")
+                            }
+                            cvsData.append(cvsStr.data(using: String.Encoding.ascii)!)
+                            cvsFile!.write(cvsData)
+                            cvsFile!.synchronizeFile()
+                            cvsFile!.closeFile()
+                        }
+                    }
+                }
+                )
+            }
+            else {
+                myAlert(message: "Cannot not export VLSM Info", info: "No subnet")
+            }
+        }
+    }
+    
     @IBAction func exportClipboard(_ sender: AnyObject)
     {
         if (ipsc != nil) {
@@ -962,6 +1241,8 @@ class SubnetCalcAppDelegate: NSObject, NSApplicationDelegate, NSWindowDelegate,
         initSubnetsTab()
         initCIDRTab()
         initIPv6Tab()
+        initFLSMTab()
+        initVLSMTab()
     }
     
     func applicationWillTerminate(_ aNotification: Notification) {