diff --git a/tests/cts/net/src/android/net/cts/DnsResolverTest.java b/tests/cts/net/src/android/net/cts/DnsResolverTest.java
index 1cc49f9..28753ff 100644
--- a/tests/cts/net/src/android/net/cts/DnsResolverTest.java
+++ b/tests/cts/net/src/android/net/cts/DnsResolverTest.java
@@ -86,7 +86,6 @@
     static final int CANCEL_RETRY_TIMES = 5;
     static final int QUERY_TIMES = 10;
     static final int NXDOMAIN = 3;
-    static final int PRIVATE_DNS_SETTING_TIMEOUT_MS = 6_000;
 
     private ContentResolver mCR;
     private ConnectivityManager mCM;
@@ -107,32 +106,15 @@
         mExecutorInline = (Runnable r) -> r.run();
         mCR = getContext().getContentResolver();
         mCtsNetUtils = new CtsNetUtils(getContext());
-        storePrivateDnsSetting();
+        mCtsNetUtils.storePrivateDnsSetting();
     }
 
     @Override
     protected void tearDown() throws Exception {
-        restorePrivateDnsSetting();
+        mCtsNetUtils.restorePrivateDnsSetting();
         super.tearDown();
     }
 
-    private void storePrivateDnsSetting() {
-        // Store private DNS setting
-        mOldMode = Settings.Global.getString(mCR, Settings.Global.PRIVATE_DNS_MODE);
-        mOldDnsSpecifier = Settings.Global.getString(mCR, Settings.Global.PRIVATE_DNS_SPECIFIER);
-    }
-
-    private void restorePrivateDnsSetting() throws InterruptedException {
-        // restore private DNS setting
-        Settings.Global.putString(mCR, Settings.Global.PRIVATE_DNS_MODE, mOldMode);
-        if ("hostname".equals(mOldMode)) {
-            Settings.Global.putString(
-                mCR, Settings.Global.PRIVATE_DNS_SPECIFIER, mOldDnsSpecifier);
-            mCtsNetUtils.awaitPrivateDnsSetting("restorePrivateDnsSetting timeout",
-                    mCM.getActiveNetwork(), mOldDnsSpecifier, PRIVATE_DNS_SETTING_TIMEOUT_MS, true);
-        }
-    }
-
     private static String byteArrayToHexString(byte[] bytes) {
         char[] hexChars = new char[bytes.length * 2];
         for (int i = 0; i < bytes.length; ++i) {
@@ -416,16 +398,13 @@
         final String msg = "RawQuery " + TEST_NX_DOMAIN + " with private DNS";
         // Enable private DNS strict mode and set server to dns.google before doing NxDomain test.
         // b/144521720
-        Settings.Global.putString(mCR, Settings.Global.PRIVATE_DNS_MODE, "hostname");
-        Settings.Global.putString(mCR,
-                Settings.Global.PRIVATE_DNS_SPECIFIER, GOOGLE_PRIVATE_DNS_SERVER);
+        mCtsNetUtils.setPrivateDnsStrictMode(GOOGLE_PRIVATE_DNS_SERVER);
         for (Network network :  getTestableNetworks()) {
             final Network networkForPrivateDns =
                     (network != null) ? network : mCM.getActiveNetwork();
             assertNotNull("Can't find network to await private DNS on", networkForPrivateDns);
             mCtsNetUtils.awaitPrivateDnsSetting(msg + " wait private DNS setting timeout",
-                    networkForPrivateDns, GOOGLE_PRIVATE_DNS_SERVER,
-                    PRIVATE_DNS_SETTING_TIMEOUT_MS, true);
+                    networkForPrivateDns, GOOGLE_PRIVATE_DNS_SERVER, true);
             final VerifyCancelCallback callback = new VerifyCancelCallback(msg);
             mDns.rawQuery(network, TEST_NX_DOMAIN, CLASS_IN, TYPE_AAAA, FLAG_NO_CACHE_LOOKUP,
                     executor, null, callback);
@@ -688,9 +667,7 @@
         final Network[] testNetworks = getTestableNetworks();
 
         // Set an invalid private DNS server
-        Settings.Global.putString(mCR, Settings.Global.PRIVATE_DNS_MODE, "hostname");
-        Settings.Global.putString(mCR,
-                Settings.Global.PRIVATE_DNS_SPECIFIER, INVALID_PRIVATE_DNS_SERVER);
+        mCtsNetUtils.setPrivateDnsStrictMode(INVALID_PRIVATE_DNS_SERVER);
         final String msg = "Test PrivateDnsBypass " + TEST_DOMAIN;
         for (Network network : testNetworks) {
             // This test cannot be ran with null network because we need to explicitly pass a
@@ -699,7 +676,7 @@
 
             // wait for private DNS setting propagating
             mCtsNetUtils.awaitPrivateDnsSetting(msg + " wait private DNS setting timeout",
-                    network, INVALID_PRIVATE_DNS_SERVER, PRIVATE_DNS_SETTING_TIMEOUT_MS, false);
+                    network, INVALID_PRIVATE_DNS_SERVER, false);
 
             final CountDownLatch latch = new CountDownLatch(1);
             final DnsResolver.Callback<List<InetAddress>> errorCallback =
diff --git a/tests/cts/net/src/android/net/cts/MultinetworkApiTest.java b/tests/cts/net/src/android/net/cts/MultinetworkApiTest.java
index f123187..985e313 100644
--- a/tests/cts/net/src/android/net/cts/MultinetworkApiTest.java
+++ b/tests/cts/net/src/android/net/cts/MultinetworkApiTest.java
@@ -41,7 +41,6 @@
 
     private static final String TAG = "MultinetworkNativeApiTest";
     static final String GOOGLE_PRIVATE_DNS_SERVER = "dns.google";
-    static final int PRIVATE_DNS_SETTING_TIMEOUT_MS = 2_000;
 
     /**
      * @return 0 on success
@@ -69,7 +68,7 @@
         mCM = (ConnectivityManager) getContext().getSystemService(Context.CONNECTIVITY_SERVICE);
         mCR = getContext().getContentResolver();
         mCtsNetUtils = new CtsNetUtils(getContext());
-        storePrivateDnsSetting();
+        mCtsNetUtils.storePrivateDnsSetting();
     }
 
     @Override
@@ -77,18 +76,6 @@
         super.tearDown();
     }
 
-    private void storePrivateDnsSetting() {
-        // Store private DNS setting
-        mOldMode = Settings.Global.getString(mCR, Settings.Global.PRIVATE_DNS_MODE);
-        mOldDnsSpecifier = Settings.Global.getString(mCR, Settings.Global.PRIVATE_DNS_SPECIFIER);
-    }
-
-    private void restorePrivateDnsSetting() {
-        // restore private DNS setting
-        Settings.Global.putString(mCR, Settings.Global.PRIVATE_DNS_MODE, mOldMode);
-        Settings.Global.putString(mCR, Settings.Global.PRIVATE_DNS_SPECIFIER, mOldDnsSpecifier);
-    }
-
     private Network[] getTestableNetworks() {
         final ArrayList<Network> testableNetworks = new ArrayList<Network>();
         for (Network network : mCM.getAllNetworks()) {
@@ -239,17 +226,15 @@
         // Enable private DNS strict mode and set server to dns.google before doing NxDomain test.
         // b/144521720
         try {
-            Settings.Global.putString(mCR, Settings.Global.PRIVATE_DNS_MODE, "hostname");
-            Settings.Global.putString(mCR,
-                    Settings.Global.PRIVATE_DNS_SPECIFIER, GOOGLE_PRIVATE_DNS_SERVER);
+            mCtsNetUtils.setPrivateDnsStrictMode(GOOGLE_PRIVATE_DNS_SERVER);
             for (Network network : getTestableNetworks()) {
               // Wait for private DNS setting to propagate.
               mCtsNetUtils.awaitPrivateDnsSetting("NxDomain test wait private DNS setting timeout",
-                        network, GOOGLE_PRIVATE_DNS_SERVER, PRIVATE_DNS_SETTING_TIMEOUT_MS, true);
+                        network, GOOGLE_PRIVATE_DNS_SERVER, true);
               runResNnxDomainCheck(network.getNetworkHandle());
             }
         } finally {
-            restorePrivateDnsSetting();
+            mCtsNetUtils.restorePrivateDnsSetting();
         }
     }
 }
diff --git a/tests/cts/net/util/java/android/net/cts/util/CtsNetUtils.java b/tests/cts/net/util/java/android/net/cts/util/CtsNetUtils.java
index 824146f..f39b184 100644
--- a/tests/cts/net/util/java/android/net/cts/util/CtsNetUtils.java
+++ b/tests/cts/net/util/java/android/net/cts/util/CtsNetUtils.java
@@ -17,6 +17,7 @@
 package android.net.cts.util;
 
 import static android.Manifest.permission.NETWORK_SETTINGS;
+import static android.net.ConnectivityManager.PRIVATE_DNS_MODE_OPPORTUNISTIC;
 import static android.net.NetworkCapabilities.NET_CAPABILITY_INTERNET;
 import static android.net.NetworkCapabilities.TRANSPORT_CELLULAR;
 
@@ -28,6 +29,7 @@
 import android.annotation.NonNull;
 import android.content.BroadcastReceiver;
 import android.content.Context;
+import android.content.ContentResolver;
 import android.content.Intent;
 import android.content.IntentFilter;
 import android.net.ConnectivityManager;
@@ -39,6 +41,7 @@
 import android.net.NetworkInfo.State;
 import android.net.NetworkRequest;
 import android.net.wifi.WifiManager;
+import android.provider.Settings;
 import android.system.Os;
 import android.system.OsConstants;
 import android.util.Log;
@@ -59,6 +62,7 @@
     private static final int SOCKET_TIMEOUT_MS = 2000;
     private static final int PRIVATE_DNS_PROBE_MS = 1_000;
 
+    public static final int PRIVATE_DNS_SETTING_TIMEOUT_MS = 6_000;
     public static final int HTTP_PORT = 80;
     public static final String TEST_HOST = "connectivitycheck.gstatic.com";
     public static final String HTTP_REQUEST =
@@ -69,15 +73,19 @@
     public static final String NETWORK_CALLBACK_ACTION =
             "ConnectivityManagerTest.NetworkCallbackAction";
 
-    private Context mContext;
-    private ConnectivityManager mCm;
-    private WifiManager mWifiManager;
+    private final Context mContext;
+    private final ConnectivityManager mCm;
+    private final ContentResolver mCR;
+    private final WifiManager mWifiManager;
     private TestNetworkCallback mCellNetworkCallback;
+    private String mOldPrivateDnsMode;
+    private String mOldPrivateDnsSpecifier;
 
     public CtsNetUtils(Context context) {
         mContext = context;
         mCm = (ConnectivityManager) mContext.getSystemService(Context.CONNECTIVITY_SERVICE);
         mWifiManager = (WifiManager) mContext.getSystemService(Context.WIFI_SERVICE);
+        mCR = context.getContentResolver();
     }
 
     // Toggle WiFi twice, leaving it in the state it started in
@@ -249,9 +257,51 @@
         return s;
     }
 
+    public void storePrivateDnsSetting() {
+        // Store private DNS setting
+        mOldPrivateDnsMode = Settings.Global.getString(mCR, Settings.Global.PRIVATE_DNS_MODE);
+        mOldPrivateDnsSpecifier = Settings.Global.getString(mCR,
+                Settings.Global.PRIVATE_DNS_SPECIFIER);
+        // It's possible that there is no private DNS default value in Settings.
+        // Give it a proper default mode which is opportunistic mode.
+        if (mOldPrivateDnsMode == null) {
+            mOldPrivateDnsSpecifier = "";
+            mOldPrivateDnsMode = PRIVATE_DNS_MODE_OPPORTUNISTIC;
+            Settings.Global.putString(mCR,
+                    Settings.Global.PRIVATE_DNS_SPECIFIER, mOldPrivateDnsSpecifier);
+            Settings.Global.putString(mCR, Settings.Global.PRIVATE_DNS_MODE, mOldPrivateDnsMode);
+        }
+    }
+
+    public void restorePrivateDnsSetting() throws InterruptedException {
+        if (mOldPrivateDnsMode == null || mOldPrivateDnsSpecifier == null) {
+            return;
+        }
+        // restore private DNS setting
+        if ("hostname".equals(mOldPrivateDnsMode)) {
+            setPrivateDnsStrictMode(mOldPrivateDnsSpecifier);
+            awaitPrivateDnsSetting("restorePrivateDnsSetting timeout",
+                    mCm.getActiveNetwork(),
+                    mOldPrivateDnsSpecifier, true);
+        } else {
+            Settings.Global.putString(mCR, Settings.Global.PRIVATE_DNS_MODE, mOldPrivateDnsMode);
+        }
+    }
+
+    public void setPrivateDnsStrictMode(String server) {
+        // To reduce flake rate, set PRIVATE_DNS_SPECIFIER before PRIVATE_DNS_MODE. This ensures
+        // that if the previous private DNS mode was not "hostname", the system only sees one
+        // EVENT_PRIVATE_DNS_SETTINGS_CHANGED event instead of two.
+        Settings.Global.putString(mCR, Settings.Global.PRIVATE_DNS_SPECIFIER, server);
+        final String mode = Settings.Global.getString(mCR, Settings.Global.PRIVATE_DNS_MODE);
+        // If current private DNS mode is "hostname", we only need to set PRIVATE_DNS_SPECIFIER.
+        if (!"hostname".equals(mode)) {
+            Settings.Global.putString(mCR, Settings.Global.PRIVATE_DNS_MODE, "hostname");
+        }
+    }
+
     public void awaitPrivateDnsSetting(@NonNull String msg, @NonNull Network network,
-            @NonNull String server, int timeoutMs,
-            boolean requiresValidatedServers) throws InterruptedException {
+            @NonNull String server, boolean requiresValidatedServers) throws InterruptedException {
         CountDownLatch latch = new CountDownLatch(1);
         NetworkRequest request = new NetworkRequest.Builder().clearCapabilities().build();
         NetworkCallback callback = new NetworkCallback() {
@@ -266,7 +316,7 @@
             }
         };
         mCm.registerNetworkCallback(request, callback);
-        assertTrue(msg, latch.await(timeoutMs, TimeUnit.MILLISECONDS));
+        assertTrue(msg, latch.await(PRIVATE_DNS_SETTING_TIMEOUT_MS, TimeUnit.MILLISECONDS));
         mCm.unregisterNetworkCallback(callback);
         // Wait some time for NetworkMonitor's private DNS probe to complete. If we do not do
         // this, then the test could complete before the NetworkMonitor private DNS probe