diff --git a/framework/api/module-lib-current.txt b/framework/api/module-lib-current.txt
index 65a44f0..5b64d52 100644
--- a/framework/api/module-lib-current.txt
+++ b/framework/api/module-lib-current.txt
@@ -51,6 +51,14 @@
     field public static final String TEST_TAP_PREFIX = "testtap";
   }
 
+  public final class TestNetworkSpecifier extends android.net.NetworkSpecifier implements android.os.Parcelable {
+    ctor public TestNetworkSpecifier(@NonNull String);
+    method public int describeContents();
+    method @Nullable public String getInterfaceName();
+    method public void writeToParcel(@NonNull android.os.Parcel, int);
+    field @NonNull public static final android.os.Parcelable.Creator<android.net.TestNetworkSpecifier> CREATOR;
+  }
+
   public final class VpnTransportInfo implements android.os.Parcelable android.net.TransportInfo {
     ctor public VpnTransportInfo(int);
     method public int describeContents();
diff --git a/framework/src/android/net/NetworkRequest.java b/framework/src/android/net/NetworkRequest.java
index 59b539a..aa69756 100644
--- a/framework/src/android/net/NetworkRequest.java
+++ b/framework/src/android/net/NetworkRequest.java
@@ -31,6 +31,7 @@
 import static android.net.NetworkCapabilities.NET_CAPABILITY_TEMPORARILY_NOT_METERED;
 import static android.net.NetworkCapabilities.NET_CAPABILITY_TRUSTED;
 import static android.net.NetworkCapabilities.NET_CAPABILITY_VALIDATED;
+import static android.net.NetworkCapabilities.TRANSPORT_TEST;
 
 import android.annotation.NonNull;
 import android.annotation.Nullable;
@@ -387,11 +388,17 @@
                 return setNetworkSpecifier(new TelephonyNetworkSpecifier.Builder()
                         .setSubscriptionId(subId).build());
             } catch (NumberFormatException nfe) {
-                // A StringNetworkSpecifier does not accept null or empty ("") strings. When network
-                // specifiers were strings a null string and an empty string were considered
-                // equivalent. Hence no meaning is attached to a null or empty ("") string.
-                return setNetworkSpecifier(TextUtils.isEmpty(networkSpecifier) ? null
-                        : new StringNetworkSpecifier(networkSpecifier));
+                // An EthernetNetworkSpecifier or TestNetworkSpecifier does not accept null or empty
+                // ("") strings. When network specifiers were strings a null string and an empty
+                // string were considered equivalent. Hence no meaning is attached to a null or
+                // empty ("") string.
+                if (TextUtils.isEmpty(networkSpecifier)) {
+                    return setNetworkSpecifier((NetworkSpecifier) null);
+                } else if (mNetworkCapabilities.hasTransport(TRANSPORT_TEST)) {
+                    return setNetworkSpecifier(new TestNetworkSpecifier(networkSpecifier));
+                } else {
+                    return setNetworkSpecifier(new EthernetNetworkSpecifier(networkSpecifier));
+                }
             }
         }
 
diff --git a/framework/src/android/net/TestNetworkSpecifier.java b/framework/src/android/net/TestNetworkSpecifier.java
new file mode 100644
index 0000000..b7470a5
--- /dev/null
+++ b/framework/src/android/net/TestNetworkSpecifier.java
@@ -0,0 +1,97 @@
+/*
+ * Copyright (C) 2021 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 android.annotation.NonNull;
+import android.annotation.Nullable;
+import android.annotation.SystemApi;
+import android.os.Parcel;
+import android.os.Parcelable;
+import android.text.TextUtils;
+
+import com.android.internal.util.Preconditions;
+
+import java.util.Objects;
+
+/**
+ * A {@link NetworkSpecifier} used to identify test interfaces.
+ *
+ * @see TestNetworkManager
+ * @hide
+ */
+@SystemApi(client = SystemApi.Client.MODULE_LIBRARIES)
+public final class TestNetworkSpecifier extends NetworkSpecifier implements Parcelable {
+
+    /**
+     * Name of the network interface.
+     */
+    @NonNull
+    private final String mInterfaceName;
+
+    public TestNetworkSpecifier(@NonNull String interfaceName) {
+        Preconditions.checkStringNotEmpty(interfaceName);
+        mInterfaceName = interfaceName;
+    }
+
+    // This may be null in the future to support specifiers based on data other than the interface
+    // name.
+    @Nullable
+    public String getInterfaceName() {
+        return mInterfaceName;
+    }
+
+    @Override
+    public boolean canBeSatisfiedBy(@Nullable NetworkSpecifier other) {
+        return equals(other);
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (!(o instanceof TestNetworkSpecifier)) return false;
+        return TextUtils.equals(mInterfaceName, ((TestNetworkSpecifier) o).mInterfaceName);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hashCode(mInterfaceName);
+    }
+
+    @Override
+    public String toString() {
+        return "TestNetworkSpecifier (" + mInterfaceName + ")";
+    }
+
+    @Override
+    public int describeContents() {
+        return 0;
+    }
+
+    @Override
+    public void writeToParcel(@NonNull Parcel dest, int flags) {
+        dest.writeString(mInterfaceName);
+    }
+
+    public static final @NonNull Creator<TestNetworkSpecifier> CREATOR =
+            new Creator<TestNetworkSpecifier>() {
+        public TestNetworkSpecifier createFromParcel(Parcel in) {
+            return new TestNetworkSpecifier(in.readString());
+        }
+        public TestNetworkSpecifier[] newArray(int size) {
+            return new TestNetworkSpecifier[size];
+        }
+    };
+}
diff --git a/services/core/java/com/android/server/TestNetworkService.java b/services/core/java/com/android/server/TestNetworkService.java
index 55408ea..ee61067 100644
--- a/services/core/java/com/android/server/TestNetworkService.java
+++ b/services/core/java/com/android/server/TestNetworkService.java
@@ -33,8 +33,8 @@
 import android.net.NetworkCapabilities;
 import android.net.NetworkProvider;
 import android.net.RouteInfo;
-import android.net.StringNetworkSpecifier;
 import android.net.TestNetworkInterface;
+import android.net.TestNetworkSpecifier;
 import android.net.util.NetdService;
 import android.os.Binder;
 import android.os.Handler;
@@ -242,7 +242,7 @@
         nc.addCapability(NetworkCapabilities.NET_CAPABILITY_NOT_SUSPENDED);
         nc.addCapability(NetworkCapabilities.NET_CAPABILITY_NOT_RESTRICTED);
         nc.addCapability(NetworkCapabilities.NET_CAPABILITY_NOT_VCN_MANAGED);
-        nc.setNetworkSpecifier(new StringNetworkSpecifier(iface));
+        nc.setNetworkSpecifier(new TestNetworkSpecifier(iface));
         nc.setAdministratorUids(administratorUids);
         if (!isMetered) {
             nc.addCapability(NetworkCapabilities.NET_CAPABILITY_NOT_METERED);
diff --git a/tests/net/common/java/android/net/NetworkCapabilitiesTest.java b/tests/net/common/java/android/net/NetworkCapabilitiesTest.java
index 5d0e016..e84b992 100644
--- a/tests/net/common/java/android/net/NetworkCapabilitiesTest.java
+++ b/tests/net/common/java/android/net/NetworkCapabilitiesTest.java
@@ -68,6 +68,7 @@
 import androidx.test.runner.AndroidJUnit4;
 
 import com.android.modules.utils.build.SdkLevel;
+import com.android.testutils.CompatUtil;
 import com.android.testutils.DevSdkIgnoreRule;
 import com.android.testutils.DevSdkIgnoreRule.IgnoreUpTo;
 
@@ -211,7 +212,7 @@
         nc1 = new NetworkCapabilities().addTransportType(TRANSPORT_WIFI);
         nc2 = new NetworkCapabilities()
                 .addTransportType(TRANSPORT_WIFI)
-                .setNetworkSpecifier(new StringNetworkSpecifier("specs"));
+                .setNetworkSpecifier(CompatUtil.makeEthernetNetworkSpecifier("eth42"));
         assertNotEquals("", nc1.describeImmutableDifferences(nc2));
         assertEquals("", nc1.describeImmutableDifferences(nc1));
     }
@@ -671,7 +672,7 @@
         NetworkCapabilities nc1 = new NetworkCapabilities();
         nc1.addTransportType(TRANSPORT_CELLULAR).addTransportType(TRANSPORT_WIFI);
         try {
-            nc1.setNetworkSpecifier(new StringNetworkSpecifier("specs"));
+            nc1.setNetworkSpecifier(CompatUtil.makeEthernetNetworkSpecifier("eth0"));
             fail("Cannot set NetworkSpecifier on a NetworkCapability with multiple transports!");
         } catch (IllegalStateException expected) {
             // empty
@@ -680,7 +681,7 @@
         // Sequence 2: Transport + NetworkSpecifier + Transport
         NetworkCapabilities nc2 = new NetworkCapabilities();
         nc2.addTransportType(TRANSPORT_CELLULAR).setNetworkSpecifier(
-                new StringNetworkSpecifier("specs"));
+                CompatUtil.makeEthernetNetworkSpecifier("testtap3"));
         try {
             nc2.addTransportType(TRANSPORT_WIFI);
             fail("Cannot set a second TransportType of a network which has a NetworkSpecifier!");
diff --git a/tests/net/common/java/android/net/NetworkProviderTest.kt b/tests/net/common/java/android/net/NetworkProviderTest.kt
index bcc9072..340e6f9 100644
--- a/tests/net/common/java/android/net/NetworkProviderTest.kt
+++ b/tests/net/common/java/android/net/NetworkProviderTest.kt
@@ -27,6 +27,7 @@
 import android.os.Looper
 import androidx.test.InstrumentationRegistry
 import com.android.net.module.util.ArrayTrackRecord
+import com.android.testutils.CompatUtil
 import com.android.testutils.DevSdkIgnoreRule.IgnoreUpTo
 import com.android.testutils.DevSdkIgnoreRunner
 import com.android.testutils.isDevSdkInRange
@@ -102,7 +103,8 @@
         mCm.registerNetworkProvider(provider)
         assertNotEquals(provider.getProviderId(), NetworkProvider.ID_NONE)
 
-        val specifier = StringNetworkSpecifier(UUID.randomUUID().toString())
+        val specifier = CompatUtil.makeTestNetworkSpecifier(
+                UUID.randomUUID().toString())
         val nr: NetworkRequest = NetworkRequest.Builder()
                 .addTransportType(TRANSPORT_TEST)
                 .setNetworkSpecifier(specifier)
@@ -183,7 +185,8 @@
 
         mCm.registerNetworkProvider(provider)
 
-        val specifier = StringNetworkSpecifier(UUID.randomUUID().toString())
+        val specifier = CompatUtil.makeTestNetworkSpecifier(
+                UUID.randomUUID().toString())
         val nr: NetworkRequest = NetworkRequest.Builder()
                 .addTransportType(TRANSPORT_TEST)
                 .setNetworkSpecifier(specifier)
diff --git a/tests/net/java/com/android/server/connectivity/MultipathPolicyTrackerTest.java b/tests/net/java/com/android/server/connectivity/MultipathPolicyTrackerTest.java
index 950d716..38f6d7f 100644
--- a/tests/net/java/com/android/server/connectivity/MultipathPolicyTrackerTest.java
+++ b/tests/net/java/com/android/server/connectivity/MultipathPolicyTrackerTest.java
@@ -46,12 +46,12 @@
 import android.content.pm.ApplicationInfo;
 import android.content.res.Resources;
 import android.net.ConnectivityManager;
+import android.net.EthernetNetworkSpecifier;
 import android.net.Network;
 import android.net.NetworkCapabilities;
 import android.net.NetworkPolicy;
 import android.net.NetworkPolicyManager;
 import android.net.NetworkTemplate;
-import android.net.StringNetworkSpecifier;
 import android.net.TelephonyNetworkSpecifier;
 import android.os.Handler;
 import android.os.UserHandle;
@@ -240,7 +240,7 @@
         NetworkCapabilities capabilities = new NetworkCapabilities()
                 .addCapability(NET_CAPABILITY_INTERNET)
                 .addTransportType(TRANSPORT_CELLULAR)
-                .setNetworkSpecifier(new StringNetworkSpecifier("234"));
+                .setNetworkSpecifier(new EthernetNetworkSpecifier("eth234"));
         if (!roaming) {
             capabilities.addCapability(NET_CAPABILITY_NOT_ROAMING);
         }