diff --git a/Tethering/src/com/android/networkstack/tethering/PrivateAddressCoordinator.java b/Tethering/src/com/android/networkstack/tethering/PrivateAddressCoordinator.java
index 9fc1d7e..4f616cd 100644
--- a/Tethering/src/com/android/networkstack/tethering/PrivateAddressCoordinator.java
+++ b/Tethering/src/com/android/networkstack/tethering/PrivateAddressCoordinator.java
@@ -80,11 +80,6 @@
     private final SparseArray<LinkAddress> mCachedAddresses;
 
     public PrivateAddressCoordinator(Context context, TetheringConfiguration config) {
-        this(context, config, new ArrayList<>(Arrays.asList(new IpPrefix("192.168.0.0/16"))));
-    }
-
-    public PrivateAddressCoordinator(Context context, TetheringConfiguration config,
-            List<IpPrefix> prefixPools) {
         mDownstreams = new ArraySet<>();
         mUpstreamPrefixMap = new ArrayMap<>();
         mConnectivityMgr = (ConnectivityManager) context.getSystemService(
@@ -95,7 +90,11 @@
         mCachedAddresses.put(TETHERING_BLUETOOTH, new LinkAddress(LEGACY_BLUETOOTH_IFACE_ADDRESS));
         mCachedAddresses.put(TETHERING_WIFI_P2P, new LinkAddress(LEGACY_WIFI_P2P_IFACE_ADDRESS));
 
-        mTetheringPrefixes = prefixPools;
+        mTetheringPrefixes = new ArrayList<>(Arrays.asList(new IpPrefix("192.168.0.0/16")));
+        if (config.isSelectAllPrefixRangeEnabled()) {
+            mTetheringPrefixes.add(new IpPrefix("172.16.0.0/12"));
+            mTetheringPrefixes.add(new IpPrefix("10.0.0.0/8"));
+        }
     }
 
     /**
diff --git a/Tethering/src/com/android/networkstack/tethering/TetheringConfiguration.java b/Tethering/src/com/android/networkstack/tethering/TetheringConfiguration.java
index 5783805..799637c 100644
--- a/Tethering/src/com/android/networkstack/tethering/TetheringConfiguration.java
+++ b/Tethering/src/com/android/networkstack/tethering/TetheringConfiguration.java
@@ -40,7 +40,6 @@
 import java.util.Collection;
 import java.util.StringJoiner;
 
-
 /**
  * A utility class to encapsulate the various tethering configuration elements.
  *
@@ -88,6 +87,13 @@
             "use_legacy_wifi_p2p_dedicated_ip";
 
     /**
+     * Flag use to enable select all prefix ranges feature.
+     * TODO: Remove this flag if there are no problems after M-2020-12 rolls out.
+     */
+    public static final String TETHER_ENABLE_SELECT_ALL_PREFIX_RANGES =
+            "tether_enable_select_all_prefix_ranges";
+
+    /**
      * Default value that used to periodic polls tether offload stats from tethering offload HAL
      * to make the data warnings work.
      */
@@ -118,6 +124,8 @@
     private final boolean mEnableBpfOffload;
     private final boolean mEnableWifiP2pDedicatedIp;
 
+    private final boolean mEnableSelectAllPrefixRange;
+
     public TetheringConfiguration(Context ctx, SharedLog log, int id) {
         final SharedLog configLog = log.forSubComponent("config");
 
@@ -164,6 +172,11 @@
                 R.bool.config_tether_enable_legacy_wifi_p2p_dedicated_ip,
                 false /* defaultValue */);
 
+        // Flags should normally not be booleans, but this is a kill-switch flag that is only used
+        // to turn off the feature, so binary rollback problems do not apply.
+        mEnableSelectAllPrefixRange = getDeviceConfigBoolean(
+                TETHER_ENABLE_SELECT_ALL_PREFIX_RANGES, true /* defaultValue */);
+
         configLog.log(toString());
     }
 
@@ -249,6 +262,9 @@
 
         pw.print("enableWifiP2pDedicatedIp: ");
         pw.println(mEnableWifiP2pDedicatedIp);
+
+        pw.print("mEnableSelectAllPrefixRange: ");
+        pw.println(mEnableSelectAllPrefixRange);
     }
 
     /** Returns the string representation of this object.*/
@@ -310,6 +326,10 @@
         return mEnableBpfOffload;
     }
 
+    public boolean isSelectAllPrefixRangeEnabled() {
+        return mEnableSelectAllPrefixRange;
+    }
+
     private static Collection<Integer> getUpstreamIfaceTypes(Resources res, boolean dunRequired) {
         final int[] ifaceTypes = res.getIntArray(R.array.config_tether_upstream_types);
         final ArrayList<Integer> upstreamIfaceTypes = new ArrayList<>(ifaceTypes.length);
diff --git a/Tethering/tests/mts/Android.bp b/Tethering/tests/mts/Android.bp
new file mode 100644
index 0000000..f925b0a
--- /dev/null
+++ b/Tethering/tests/mts/Android.bp
@@ -0,0 +1,56 @@
+// Copyright (C) 2020 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+android_test {
+    // This tests for functionality that is not required for devices that
+    // don't use Tethering mainline module.
+    name: "MtsTetheringTest",
+
+    libs: [
+        "android.test.base",
+    ],
+
+    srcs: [
+        "src/**/*.java",
+    ],
+
+    static_libs: [
+        "androidx.test.rules",
+        // mockito-target-extended-minus-junit4 used in this lib have dependency with
+        // jni_libs libdexmakerjvmtiagent and libstaticjvmtiagent.
+        "cts-net-utils",
+        // This is needed for androidx.test.runner.AndroidJUnitRunner.
+        "ctstestrunner-axt",
+        "junit",
+        "junit-params",
+    ],
+
+    jni_libs: [
+        // For mockito extended which is pulled in from -net-utils -> net-tests-utils
+        // (mockito-target-extended-minus-junit4).
+        "libdexmakerjvmtiagent",
+        "libstaticjvmtiagent",
+    ],
+
+    platform_apis: true,
+
+    // Tag this module as a mts test artifact
+    test_suites: [
+        "general-tests",
+        "mts",
+    ],
+
+    // Include both the 32 and 64 bit versions
+    compile_multilib: "both",
+}
diff --git a/Tethering/tests/mts/AndroidManifest.xml b/Tethering/tests/mts/AndroidManifest.xml
new file mode 100644
index 0000000..6d2abca
--- /dev/null
+++ b/Tethering/tests/mts/AndroidManifest.xml
@@ -0,0 +1,34 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+ * Copyright (C) 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ -->
+
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    package="android.tethering.mts">
+
+    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
+    <uses-permission android:name="android.permission.INTERNET"/>
+
+    <application android:debuggable="true">
+        <uses-library android:name="android.test.runner" />
+    </application>
+    <instrumentation android:name="androidx.test.runner.AndroidJUnitRunner"
+                     android:targetPackage="android.tethering.mts"
+                     android:label="MTS tests of android.tethering">
+        <meta-data android:name="listener"
+            android:value="com.android.cts.runner.CtsTestRunListener" />
+    </instrumentation>
+
+</manifest>
diff --git a/Tethering/tests/mts/AndroidTest.xml b/Tethering/tests/mts/AndroidTest.xml
new file mode 100644
index 0000000..80788df
--- /dev/null
+++ b/Tethering/tests/mts/AndroidTest.xml
@@ -0,0 +1,36 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Copyright (C) 2019 The Android Open Source Project
+
+     Licensed under the Apache License, Version 2.0 (the "License");
+     you may not use this file except in compliance with the License.
+     You may obtain a copy of the License at
+
+          http://www.apache.org/licenses/LICENSE-2.0
+
+     Unless required by applicable law or agreed to in writing, software
+     distributed under the License is distributed on an "AS IS" BASIS,
+     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+     See the License for the specific language governing permissions and
+     limitations under the License.
+-->
+<configuration description="Config for MTS Tethering test cases">
+    <option name="test-suite-tag" value="mts" />
+    <option name="config-descriptor:metadata" key="component" value="networking" />
+    <!-- Instant app do not have INTERNET permission. -->
+    <option name="config-descriptor:metadata" key="parameter" value="not_instant_app" />
+    <!-- Feature is not backed by native code. -->
+    <option name="config-descriptor:metadata" key="parameter" value="not_multi_abi" />
+    <!-- Allow running this against a secondary user. -->
+    <option name="config-descriptor:metadata" key="parameter" value="secondary_user" />
+    <target_preparer class="com.android.tradefed.targetprep.suite.SuiteApkInstaller">
+        <option name="cleanup-apks" value="true" />
+        <option name="test-file-name" value="MtsTetheringTest.apk" />
+    </target_preparer>
+    <test class="com.android.tradefed.testtype.AndroidJUnitTest" >
+        <option name="package" value="android.tethering.mts" />
+    </test>
+
+    <object type="module_controller" class="com.android.tradefed.testtype.suite.module.MainlineTestModuleController">
+        <option name="mainline-module-package-name" value="com.google.android.tethering" />
+    </object>
+</configuration>
diff --git a/Tethering/tests/mts/src/android/tethering/mts/TetheringModuleTest.java b/Tethering/tests/mts/src/android/tethering/mts/TetheringModuleTest.java
new file mode 100644
index 0000000..7ffe37a
--- /dev/null
+++ b/Tethering/tests/mts/src/android/tethering/mts/TetheringModuleTest.java
@@ -0,0 +1,183 @@
+/*
+ * Copyright (C) 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package android.tethering.mts;
+
+import static android.Manifest.permission.MANAGE_TEST_NETWORKS;
+import static android.Manifest.permission.NETWORK_SETTINGS;
+import static android.Manifest.permission.READ_DEVICE_CONFIG;
+import static android.Manifest.permission.TETHER_PRIVILEGED;
+import static android.Manifest.permission.WRITE_SETTINGS;
+import static android.net.cts.util.CtsTetheringUtils.isWifiTetheringSupported;
+import static android.provider.DeviceConfig.NAMESPACE_CONNECTIVITY;
+
+import static com.android.testutils.TestNetworkTrackerKt.initTestNetwork;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.fail;
+import static org.junit.Assume.assumeTrue;
+
+import android.app.UiAutomation;
+import android.content.Context;
+import android.net.IpPrefix;
+import android.net.LinkAddress;
+import android.net.TetheringManager;
+import android.net.cts.util.CtsTetheringUtils;
+import android.net.cts.util.CtsTetheringUtils.TestTetheringEventCallback;
+import android.provider.DeviceConfig;
+
+import androidx.annotation.NonNull;
+import androidx.test.InstrumentationRegistry;
+import androidx.test.runner.AndroidJUnit4;
+
+import com.android.testutils.TestNetworkTracker;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+import java.net.InterfaceAddress;
+import java.net.NetworkInterface;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+@RunWith(AndroidJUnit4.class)
+public class TetheringModuleTest {
+    private Context mContext;
+    private TetheringManager mTm;
+    private CtsTetheringUtils mCtsTetheringUtils;
+
+    private UiAutomation mUiAutomation =
+            InstrumentationRegistry.getInstrumentation().getUiAutomation();
+
+    @Before
+    public void setUp() throws Exception {
+        mUiAutomation.adoptShellPermissionIdentity(MANAGE_TEST_NETWORKS, NETWORK_SETTINGS,
+                WRITE_SETTINGS, READ_DEVICE_CONFIG, TETHER_PRIVILEGED);
+        mContext = InstrumentationRegistry.getContext();
+        mTm = mContext.getSystemService(TetheringManager.class);
+        mCtsTetheringUtils = new CtsTetheringUtils(mContext);
+    }
+
+    @After
+    public void tearDown() throws Exception {
+        mUiAutomation.dropShellPermissionIdentity();
+    }
+
+    private static final String TETHER_ENABLE_SELECT_ALL_PREFIX_RANGES =
+            "tether_enable_select_all_prefix_ranges";
+    @Test
+    public void testSwitchBasePrefixRangeWhenConflict() throws Exception {
+        assumeTrue(isFeatureEnabled(TETHER_ENABLE_SELECT_ALL_PREFIX_RANGES, true));
+
+        addressConflictTest(true);
+    }
+
+    @Test
+    public void testSwitchPrefixRangeWhenConflict() throws Exception {
+        addressConflictTest(false);
+    }
+
+    private void addressConflictTest(final boolean wholeRangeConflict) throws Exception {
+        final TestTetheringEventCallback tetherEventCallback =
+                mCtsTetheringUtils.registerTetheringEventCallback();
+
+        TestNetworkTracker tnt = null;
+        try {
+            tetherEventCallback.assumeTetheringSupported();
+            assumeTrue(isWifiTetheringSupported(tetherEventCallback));
+
+            mCtsTetheringUtils.startWifiTethering(tetherEventCallback);
+
+            final List<String> tetheredIfaces = tetherEventCallback.getTetheredInterfaces();
+            assertEquals(1, tetheredIfaces.size());
+            final String wifiTetheringIface = tetheredIfaces.get(0);
+
+            NetworkInterface nif = NetworkInterface.getByName(wifiTetheringIface);
+            // Tethering downstream only have one ipv4 address.
+            final LinkAddress hotspotAddr = getFirstIpv4Address(nif);
+            assertNotNull(hotspotAddr);
+
+            final IpPrefix testPrefix = getConflictingPrefix(hotspotAddr, wholeRangeConflict);
+            assertNotNull(testPrefix);
+
+            tnt = setUpTestNetwork(
+                    new LinkAddress(testPrefix.getAddress(), testPrefix.getPrefixLength()));
+
+            tetherEventCallback.expectTetheredInterfacesChanged(null);
+            final List<String> wifiRegexs =
+                    tetherEventCallback.getTetheringInterfaceRegexps().getTetherableWifiRegexs();
+
+            tetherEventCallback.expectTetheredInterfacesChanged(wifiRegexs);
+            nif = NetworkInterface.getByName(wifiTetheringIface);
+            final LinkAddress newHotspotAddr = getFirstIpv4Address(nif);
+            assertNotNull(newHotspotAddr);
+
+            assertFalse(testPrefix.containsPrefix(
+                    new IpPrefix(newHotspotAddr.getAddress(), newHotspotAddr.getPrefixLength())));
+
+            mCtsTetheringUtils.stopWifiTethering(tetherEventCallback);
+        } finally {
+            if (tnt != null) {
+                tnt.teardown();
+            }
+            mTm.stopAllTethering();
+            mCtsTetheringUtils.unregisterTetheringEventCallback(tetherEventCallback);
+        }
+    }
+
+    private LinkAddress getFirstIpv4Address(final NetworkInterface nif) {
+        for (InterfaceAddress ia : nif.getInterfaceAddresses()) {
+            final LinkAddress addr = new LinkAddress(ia.getAddress(), ia.getNetworkPrefixLength());
+            if (addr.isIpv4()) return addr;
+        }
+        return null;
+    }
+
+    @NonNull
+    private IpPrefix getConflictingPrefix(final LinkAddress address,
+            final boolean wholeRangeConflict) {
+        if (!wholeRangeConflict) {
+            return new IpPrefix(address.getAddress(), address.getPrefixLength());
+        }
+
+        final ArrayList<IpPrefix> prefixPool = new ArrayList<>(Arrays.asList(
+                new IpPrefix("192.168.0.0/16"),
+                new IpPrefix("172.16.0.0/12"),
+                new IpPrefix("10.0.0.0/8")));
+
+        for (IpPrefix prefix : prefixPool) {
+            if (prefix.contains(address.getAddress())) return prefix;
+        }
+
+        fail("Could not find sutiable conflict prefix");
+
+        // Never go here.
+        return null;
+    }
+
+    private TestNetworkTracker setUpTestNetwork(final LinkAddress address) throws Exception {
+        return initTestNetwork(mContext, address, 10_000L /* test timeout ms*/);
+
+    }
+
+    public static boolean isFeatureEnabled(final String name, final boolean defaultValue) {
+        return DeviceConfig.getBoolean(NAMESPACE_CONNECTIVITY, name, defaultValue);
+    }
+}
diff --git a/Tethering/tests/unit/src/com/android/networkstack/tethering/PrivateAddressCoordinatorTest.java b/Tethering/tests/unit/src/com/android/networkstack/tethering/PrivateAddressCoordinatorTest.java
index 8cb80ba..41d46e5 100644
--- a/Tethering/tests/unit/src/com/android/networkstack/tethering/PrivateAddressCoordinatorTest.java
+++ b/Tethering/tests/unit/src/com/android/networkstack/tethering/PrivateAddressCoordinatorTest.java
@@ -99,9 +99,9 @@
         when(mContext.getSystemService(Context.CONNECTIVITY_SERVICE)).thenReturn(mConnectivityMgr);
         when(mConnectivityMgr.getAllNetworks()).thenReturn(mAllNetworks);
         when(mConfig.shouldEnableWifiP2pDedicatedIp()).thenReturn(false);
+        when(mConfig.isSelectAllPrefixRangeEnabled()).thenReturn(true);
         setUpIpServers();
-        mPrivateAddressCoordinator = spy(new PrivateAddressCoordinator(mContext, mConfig,
-                mTetheringPrefixes));
+        mPrivateAddressCoordinator = spy(new PrivateAddressCoordinator(mContext, mConfig));
     }
 
     private LinkAddress requestDownstreamAddress(final IpServer ipServer, boolean useLastAddress) {
diff --git a/Tethering/tests/unit/src/com/android/networkstack/tethering/TetheringConfigurationTest.java b/Tethering/tests/unit/src/com/android/networkstack/tethering/TetheringConfigurationTest.java
index dc0940c..237e2c2 100644
--- a/Tethering/tests/unit/src/com/android/networkstack/tethering/TetheringConfigurationTest.java
+++ b/Tethering/tests/unit/src/com/android/networkstack/tethering/TetheringConfigurationTest.java
@@ -131,6 +131,7 @@
         when(mResources.getBoolean(R.bool.config_tether_enable_legacy_wifi_p2p_dedicated_ip))
                 .thenReturn(false);
         initializeBpfOffloadConfiguration(true, null /* unset */);
+        initEnableSelectAllPrefixRangeFlag(null /* unset */);
 
         mHasTelephonyManager = true;
         mMockContext = new MockContext(mContext);
@@ -428,4 +429,30 @@
                 mMockContext, mLog, INVALID_SUBSCRIPTION_ID);
         assertTrue(testCfg.shouldEnableWifiP2pDedicatedIp());
     }
+
+    private void initEnableSelectAllPrefixRangeFlag(final String value) {
+        doReturn(value).when(
+                () -> DeviceConfig.getProperty(eq(NAMESPACE_CONNECTIVITY),
+                eq(TetheringConfiguration.TETHER_ENABLE_SELECT_ALL_PREFIX_RANGES)));
+    }
+
+    @Test
+    public void testSelectAllPrefixRangeFlag() throws Exception {
+        // Test default value.
+        final TetheringConfiguration defaultCfg = new TetheringConfiguration(
+                mMockContext, mLog, INVALID_SUBSCRIPTION_ID);
+        assertTrue(defaultCfg.isSelectAllPrefixRangeEnabled());
+
+        // Test disable flag.
+        initEnableSelectAllPrefixRangeFlag("false");
+        final TetheringConfiguration testDisable = new TetheringConfiguration(
+                mMockContext, mLog, INVALID_SUBSCRIPTION_ID);
+        assertFalse(testDisable.isSelectAllPrefixRangeEnabled());
+
+        // Test enable flag.
+        initEnableSelectAllPrefixRangeFlag("true");
+        final TetheringConfiguration testEnable = new TetheringConfiguration(
+                mMockContext, mLog, INVALID_SUBSCRIPTION_ID);
+        assertTrue(testEnable.isSelectAllPrefixRangeEnabled());
+    }
 }
diff --git a/Tethering/tests/unit/src/com/android/networkstack/tethering/TetheringTest.java b/Tethering/tests/unit/src/com/android/networkstack/tethering/TetheringTest.java
index 20e94b2..114cb7c 100644
--- a/Tethering/tests/unit/src/com/android/networkstack/tethering/TetheringTest.java
+++ b/Tethering/tests/unit/src/com/android/networkstack/tethering/TetheringTest.java
@@ -456,11 +456,7 @@
         @Override
         public PrivateAddressCoordinator getPrivateAddressCoordinator(Context ctx,
                 TetheringConfiguration cfg) {
-            final ArrayList<IpPrefix> prefixPool = new ArrayList<>(Arrays.asList(
-                    new IpPrefix("192.168.0.0/16"),
-                    new IpPrefix("172.16.0.0/12"),
-                    new IpPrefix("10.0.0.0/8")));
-            mPrivateAddressCoordinator = spy(new PrivateAddressCoordinator(ctx, cfg, prefixPool));
+            mPrivateAddressCoordinator = super.getPrivateAddressCoordinator(ctx, cfg);
             return mPrivateAddressCoordinator;
         }
     }