diff --git a/tests/cts/hostside/AndroidTest.xml b/tests/cts/hostside/AndroidTest.xml
index ad7f81b..4a2e2e3 100644
--- a/tests/cts/hostside/AndroidTest.xml
+++ b/tests/cts/hostside/AndroidTest.xml
@@ -15,6 +15,7 @@
 -->
 <configuration description="Config for CTS net host test cases">
     <option name="config-descriptor:metadata" key="component" value="networking" />
+    <target_preparer class="com.android.cts.net.NetPolicyTestsPreparer" />
     <test class="com.android.compatibility.common.tradefed.testtype.JarHostTest" >
         <option name="jar" value="CtsHostsideNetworkTests.jar" />
         <option name="runtime-hint" value="3m56s" />
diff --git a/tests/cts/hostside/src/com/android/cts/net/NetPolicyTestsPreparer.java b/tests/cts/hostside/src/com/android/cts/net/NetPolicyTestsPreparer.java
new file mode 100644
index 0000000..9b19554
--- /dev/null
+++ b/tests/cts/hostside/src/com/android/cts/net/NetPolicyTestsPreparer.java
@@ -0,0 +1,75 @@
+/*
+ * Copyright (C) 2017 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 com.android.cts.net;
+
+import com.android.tradefed.build.IBuildInfo;
+import com.android.tradefed.device.DeviceNotAvailableException;
+import com.android.tradefed.device.ITestDevice;
+import com.android.tradefed.log.LogUtil;
+import com.android.tradefed.targetprep.ITargetCleaner;
+import com.android.tradefed.targetprep.ITargetPreparer;
+
+public class NetPolicyTestsPreparer implements ITargetPreparer, ITargetCleaner {
+    private final static String KEY_PAROLE_DURATION = "parole_duration";
+    private final static String DESIRED_PAROLE_DURATION = "0";
+
+    private boolean mAppIdleConstsUpdated;
+    private String mOriginalAppIdleConsts;
+
+    @Override
+    public void setUp(ITestDevice device, IBuildInfo buildInfo) throws DeviceNotAvailableException {
+        updateParoleDuration(device);
+        LogUtil.CLog.d("Original app_idle_constants: " + mOriginalAppIdleConsts);
+    }
+
+    @Override
+    public void tearDown(ITestDevice device, IBuildInfo buildInfo, Throwable throwable)
+            throws DeviceNotAvailableException {
+        if (mAppIdleConstsUpdated) {
+            executeCmd(device, "settings put global app_idle_constants " + mOriginalAppIdleConsts);
+        }
+    }
+
+    /**
+     * Updates parole_duration with the desired value.
+     */
+    private void updateParoleDuration(ITestDevice device) throws DeviceNotAvailableException {
+        mOriginalAppIdleConsts = executeCmd(device, "settings get global app_idle_constants");
+        String newAppIdleConstants;
+        final String newConstant = KEY_PAROLE_DURATION + "=" + DESIRED_PAROLE_DURATION;
+        if (mOriginalAppIdleConsts == null || "null".equals(mOriginalAppIdleConsts)) {
+            // app_idle_constants is initially empty, so just assign the desired value.
+            newAppIdleConstants = newConstant;
+        } else if (mOriginalAppIdleConsts.contains(KEY_PAROLE_DURATION)) {
+            // app_idle_constants contains parole_duration, so replace it with the desired value.
+            newAppIdleConstants = mOriginalAppIdleConsts.replaceAll(
+                    KEY_PAROLE_DURATION + "=\\d+", newConstant);
+        } else {
+            // app_idle_constants didn't have parole_duration, so append the desired value.
+            newAppIdleConstants = mOriginalAppIdleConsts + "," + newConstant;
+        }
+        executeCmd(device, "settings put global app_idle_constants " + newAppIdleConstants);
+        mAppIdleConstsUpdated = true;
+    }
+
+    private String executeCmd(ITestDevice device, String cmd)
+            throws DeviceNotAvailableException {
+        final String output = device.executeShellCommand(cmd).trim();
+        LogUtil.CLog.d("Output for '%s': %s", cmd, output);
+        return output;
+    }
+}