diff --git a/Tethering/tests/integration/src/android/net/EthernetTetheringTest.java b/Tethering/tests/integration/src/android/net/EthernetTetheringTest.java
index b92cff7..da69a8d 100644
--- a/Tethering/tests/integration/src/android/net/EthernetTetheringTest.java
+++ b/Tethering/tests/integration/src/android/net/EthernetTetheringTest.java
@@ -67,16 +67,13 @@
 import static org.junit.Assume.assumeFalse;
 import static org.junit.Assume.assumeTrue;
 
-import android.app.UiAutomation;
 import android.content.Context;
-import android.content.pm.PackageManager;
 import android.net.EthernetManager.TetheredInterfaceCallback;
 import android.net.EthernetManager.TetheredInterfaceRequest;
 import android.net.TetheringManager.StartTetheringCallback;
 import android.net.TetheringManager.TetheringEventCallback;
 import android.net.TetheringManager.TetheringRequest;
 import android.net.TetheringTester.TetheredDevice;
-import android.net.cts.util.CtsNetUtils;
 import android.os.Build;
 import android.os.Handler;
 import android.os.HandlerThread;
@@ -88,7 +85,6 @@
 
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
-import androidx.test.InstrumentationRegistry;
 import androidx.test.filters.MediumTest;
 import androidx.test.runner.AndroidJUnit4;
 
@@ -143,17 +139,12 @@
 
 @RunWith(AndroidJUnit4.class)
 @MediumTest
-public class EthernetTetheringTest {
+public class EthernetTetheringTest extends EthernetTetheringTestBase {
     @Rule
     public final DevSdkIgnoreRule mIgnoreRule = new DevSdkIgnoreRule();
 
     private static final String TAG = EthernetTetheringTest.class.getSimpleName();
-    private static final int TIMEOUT_MS = 5000;
-    // Used to check if any tethering interface is available. Choose 200ms to be request timeout
-    // because the average interface requested time on cuttlefish@acloud is around 10ms.
-    // See TetheredInterfaceRequester.getInterface, isInterfaceForTetheringAvailable.
-    private static final int AVAILABLE_TETHER_IFACE_REQUEST_TIMEOUT_MS = 200;
-    private static final int TETHER_REACHABILITY_ATTEMPTS = 20;
+
     private static final int DUMP_POLLING_MAX_RETRY = 100;
     private static final int DUMP_POLLING_INTERVAL_MS = 50;
     // Kernel treats a confirmed UDP connection which active after two seconds as stream mode.
@@ -168,35 +159,14 @@
     // Per TX UDP packet size: ethhdr (14) + iphdr (20) + udphdr (8) + payload (2) = 44 bytes.
     private static final int TX_UDP_PACKET_SIZE = 44;
     private static final int TX_UDP_PACKET_COUNT = 123;
-    private static final long WAIT_RA_TIMEOUT_MS = 2000;
-
-    private static final MacAddress TEST_MAC = MacAddress.fromString("1:2:3:4:5:6");
-    private static final LinkAddress TEST_IP4_ADDR = new LinkAddress("10.0.0.1/24");
-    private static final LinkAddress TEST_IP6_ADDR = new LinkAddress("2001:db8:1::101/64");
-    private static final InetAddress TEST_IP4_DNS = parseNumericAddress("8.8.8.8");
-    private static final InetAddress TEST_IP6_DNS = parseNumericAddress("2001:db8:1::888");
-    private static final IpPrefix TEST_NAT64PREFIX = new IpPrefix("64:ff9b::/96");
-    private static final Inet6Address REMOTE_NAT64_ADDR =
-            (Inet6Address) parseNumericAddress("64:ff9b::808:808");
-    private static final Inet6Address REMOTE_IP6_ADDR =
-            (Inet6Address) parseNumericAddress("2002:db8:1::515:ca");
-    private static final ByteBuffer TEST_REACHABILITY_PAYLOAD =
-            ByteBuffer.wrap(new byte[] { (byte) 0x55, (byte) 0xaa });
-    private static final ByteBuffer EMPTY_PAYLOAD = ByteBuffer.wrap(new byte[0]);
 
     private static final short DNS_PORT = 53;
-    private static final short WINDOW = (short) 0x2000;
-    private static final short URGENT_POINTER = 0;
 
     private static final String DUMPSYS_TETHERING_RAWMAP_ARG = "bpfRawMap";
     private static final String DUMPSYS_RAWMAP_ARG_STATS = "--stats";
     private static final String DUMPSYS_RAWMAP_ARG_UPSTREAM4 = "--upstream4";
     private static final String LINE_DELIMITER = "\\n";
 
-    // version=6, traffic class=0x0, flowlabel=0x0;
-    private static final int VERSION_TRAFFICCLASS_FLOWLABEL = 0x60000000;
-    private static final short HOP_LIMIT = 0x40;
-
     private static final short ICMPECHO_CODE = 0x0;
     private static final short ICMPECHO_ID = 0x0;
     private static final short ICMPECHO_SEQ = 0x0;
@@ -261,27 +231,9 @@
             (byte) 0x01, (byte) 0x02, (byte) 0x03, (byte) 0x04  /* Address: 1.2.3.4 */
     };
 
-    private final Context mContext = InstrumentationRegistry.getContext();
-    private final EthernetManager mEm = mContext.getSystemService(EthernetManager.class);
-    private final TetheringManager mTm = mContext.getSystemService(TetheringManager.class);
-    private final PackageManager mPackageManager = mContext.getPackageManager();
-    private final CtsNetUtils mCtsNetUtils = new CtsNetUtils(mContext);
-
-    private TestNetworkInterface mDownstreamIface;
-    private HandlerThread mHandlerThread;
-    private Handler mHandler;
-    private TapPacketReader mDownstreamReader;
-    private TapPacketReader mUpstreamReader;
-
     private TetheredInterfaceRequester mTetheredInterfaceRequester;
     private MyTetheringEventCallback mTetheringEventCallback;
 
-    private UiAutomation mUiAutomation =
-            InstrumentationRegistry.getInstrumentation().getUiAutomation();
-    private boolean mRunTests;
-
-    private TestNetworkTracker mUpstreamTracker;
-
     @Before
     public void setUp() throws Exception {
         mHandlerThread = new HandlerThread(getClass().getSimpleName());
@@ -1068,22 +1020,6 @@
     // remote ip              public ip                           private ip
     // 8.8.8.8:443            <Upstream ip>:9876                  <TetheredDevice ip>:9876
     //
-    private static final Inet4Address REMOTE_IP4_ADDR =
-            (Inet4Address) parseNumericAddress("8.8.8.8");
-    // Used by public port and private port. Assume port 9876 has not been used yet before the
-    // testing that public port and private port are the same in the testing. Note that NAT port
-    // forwarding could be different between private port and public port.
-    // TODO: move to the start of test class.
-    private static final short LOCAL_PORT = 9876;
-    private static final short REMOTE_PORT = 433;
-    private static final byte TYPE_OF_SERVICE = 0;
-    private static final short ID = 27149;
-    private static final short FLAGS_AND_FRAGMENT_OFFSET = (short) 0x4000; // flags=DF, offset=0
-    private static final byte TIME_TO_LIVE = (byte) 0x40;
-    private static final ByteBuffer RX_PAYLOAD =
-            ByteBuffer.wrap(new byte[] { (byte) 0x12, (byte) 0x34 });
-    private static final ByteBuffer TX_PAYLOAD =
-            ByteBuffer.wrap(new byte[] { (byte) 0x56, (byte) 0x78 });
 
     private short getEthType(@NonNull final InetAddress srcIp, @NonNull final InetAddress dstIp) {
         return isAddressIpv4(srcIp, dstIp) ? (short) ETHER_TYPE_IPV4 : (short) ETHER_TYPE_IPV6;
diff --git a/Tethering/tests/integration/src/android/net/EthernetTetheringTestBase.java b/Tethering/tests/integration/src/android/net/EthernetTetheringTestBase.java
new file mode 100644
index 0000000..d58a60c
--- /dev/null
+++ b/Tethering/tests/integration/src/android/net/EthernetTetheringTestBase.java
@@ -0,0 +1,115 @@
+/*
+ * Copyright (C) 2022 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.net;
+
+import static android.net.InetAddresses.parseNumericAddress;
+
+import android.app.UiAutomation;
+import android.content.Context;
+import android.content.pm.PackageManager;
+import android.net.cts.util.CtsNetUtils;
+import android.os.Handler;
+import android.os.HandlerThread;
+
+import androidx.test.platform.app.InstrumentationRegistry;
+
+import com.android.testutils.TapPacketReader;
+import com.android.testutils.TestNetworkTracker;
+
+import java.net.Inet4Address;
+import java.net.Inet6Address;
+import java.net.InetAddress;
+import java.nio.ByteBuffer;
+
+/**
+ * TODO: Common variables or methods shared between CtsEthernetTetheringTest and
+ * MtsEthernetTetheringTest.
+ */
+public abstract class EthernetTetheringTestBase {
+    private static final String TAG = EthernetTetheringTestBase.class.getSimpleName();
+
+    protected static final int TIMEOUT_MS = 5000;
+    // Used to check if any tethering interface is available. Choose 200ms to be request timeout
+    // because the average interface requested time on cuttlefish@acloud is around 10ms.
+    // See TetheredInterfaceRequester.getInterface, isInterfaceForTetheringAvailable.
+    protected static final int AVAILABLE_TETHER_IFACE_REQUEST_TIMEOUT_MS = 200;
+    protected static final int TETHER_REACHABILITY_ATTEMPTS = 20;
+    protected static final long WAIT_RA_TIMEOUT_MS = 2000;
+
+    // Address and NAT prefix definition.
+    protected static final MacAddress TEST_MAC = MacAddress.fromString("1:2:3:4:5:6");
+    protected static final LinkAddress TEST_IP4_ADDR = new LinkAddress("10.0.0.1/24");
+    protected static final LinkAddress TEST_IP6_ADDR = new LinkAddress("2001:db8:1::101/64");
+    protected static final InetAddress TEST_IP4_DNS = parseNumericAddress("8.8.8.8");
+    protected static final InetAddress TEST_IP6_DNS = parseNumericAddress("2001:db8:1::888");
+
+    protected static final Inet4Address REMOTE_IP4_ADDR =
+            (Inet4Address) parseNumericAddress("8.8.8.8");
+    protected static final Inet6Address REMOTE_IP6_ADDR =
+            (Inet6Address) parseNumericAddress("2002:db8:1::515:ca");
+    protected static final Inet6Address REMOTE_NAT64_ADDR =
+            (Inet6Address) parseNumericAddress("64:ff9b::808:808");
+    protected static final IpPrefix TEST_NAT64PREFIX = new IpPrefix("64:ff9b::/96");
+
+    // IPv4 header definition.
+    protected static final short ID = 27149;
+    protected static final short FLAGS_AND_FRAGMENT_OFFSET = (short) 0x4000; // flags=DF, offset=0
+    protected static final byte TIME_TO_LIVE = (byte) 0x40;
+    protected static final byte TYPE_OF_SERVICE = 0;
+
+    // IPv6 header definition.
+    protected static final short HOP_LIMIT = 0x40;
+    // version=6, traffic class=0x0, flowlabel=0x0;
+    protected static final int VERSION_TRAFFICCLASS_FLOWLABEL = 0x60000000;
+
+    // UDP and TCP header definition.
+    // LOCAL_PORT is used by public port and private port. Assume port 9876 has not been used yet
+    // before the testing that public port and private port are the same in the testing. Note that
+    // NAT port forwarding could be different between private port and public port.
+    protected static final short LOCAL_PORT = 9876;
+    protected static final short REMOTE_PORT = 433;
+    protected static final short WINDOW = (short) 0x2000;
+    protected static final short URGENT_POINTER = 0;
+
+    // Payload definition.
+    protected static final ByteBuffer EMPTY_PAYLOAD = ByteBuffer.wrap(new byte[0]);
+    protected static final ByteBuffer TEST_REACHABILITY_PAYLOAD =
+            ByteBuffer.wrap(new byte[] { (byte) 0x55, (byte) 0xaa });
+    protected static final ByteBuffer RX_PAYLOAD =
+            ByteBuffer.wrap(new byte[] { (byte) 0x12, (byte) 0x34 });
+    protected static final ByteBuffer TX_PAYLOAD =
+            ByteBuffer.wrap(new byte[] { (byte) 0x56, (byte) 0x78 });
+
+    protected final Context mContext = InstrumentationRegistry.getInstrumentation().getContext();
+    protected final EthernetManager mEm = mContext.getSystemService(EthernetManager.class);
+    protected final TetheringManager mTm = mContext.getSystemService(TetheringManager.class);
+    protected final PackageManager mPackageManager = mContext.getPackageManager();
+    protected final CtsNetUtils mCtsNetUtils = new CtsNetUtils(mContext);
+    protected final UiAutomation mUiAutomation =
+            InstrumentationRegistry.getInstrumentation().getUiAutomation();
+
+    // Late initialization in setUp()
+    protected boolean mRunTests;
+    protected HandlerThread mHandlerThread;
+    protected Handler mHandler;
+
+    // Late initialization in initTetheringTester().
+    protected TapPacketReader mUpstreamReader;
+    protected TestNetworkTracker mUpstreamTracker;
+    protected TestNetworkInterface mDownstreamIface;
+    protected TapPacketReader mDownstreamReader;
+}