diff --git a/Tethering/src/com/android/networkstack/tethering/PrivateAddressCoordinator.java b/Tethering/src/com/android/networkstack/tethering/PrivateAddressCoordinator.java
index 6c0ca82..6f3e865 100644
--- a/Tethering/src/com/android/networkstack/tethering/PrivateAddressCoordinator.java
+++ b/Tethering/src/com/android/networkstack/tethering/PrivateAddressCoordinator.java
@@ -79,6 +79,7 @@
     private final TetheringConfiguration mConfig;
     // keyed by downstream type(TetheringManager.TETHERING_*).
     private final ArrayMap<AddressKey, LinkAddress> mCachedAddresses;
+    private final Random mRandom;
 
     public PrivateAddressCoordinator(Context context, TetheringConfiguration config) {
         mDownstreams = new ArraySet<>();
@@ -95,6 +96,7 @@
 
         mTetheringPrefixes = 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")));
+        mRandom = new Random();
     }
 
     /**
@@ -263,12 +265,13 @@
         // is less than 127.0.0.0 = 0x7f000000 = 2130706432.
         //
         // Additionally, it makes debug output easier to read by making the numbers smaller.
-        final int randomPrefixStart = getRandomInt() & ~prefixRangeMask & prefixMask;
+        final int randomInt = getRandomInt();
+        final int randomPrefixStart = randomInt & ~prefixRangeMask & prefixMask;
 
         // A random offset within the prefix. Used to determine the local address once the prefix
         // is selected. It does not result in an IPv4 address ending in .0, .1, or .255
-        // For a PREFIX_LENGTH of 255, this is a number between 2 and 254.
-        final int subAddress = getSanitizedSubAddr(~prefixMask);
+        // For a PREFIX_LENGTH of 24, this is a number between 2 and 254.
+        final int subAddress = getSanitizedSubAddr(randomInt, ~prefixMask);
 
         // Find a prefix length PREFIX_LENGTH between randomPrefixStart and the end of the block,
         // such that the prefix does not conflict with any upstream.
@@ -310,12 +313,12 @@
     /** Get random int which could be used to generate random address. */
     @VisibleForTesting
     public int getRandomInt() {
-        return (new Random()).nextInt();
+        return mRandom.nextInt();
     }
 
     /** Get random subAddress and avoid selecting x.x.x.0, x.x.x.1 and x.x.x.255 address. */
-    private int getSanitizedSubAddr(final int subAddrMask) {
-        final int randomSubAddr = getRandomInt() & subAddrMask;
+    private int getSanitizedSubAddr(final int randomInt, final int subAddrMask) {
+        final int randomSubAddr = randomInt & subAddrMask;
         // If prefix length > 30, the selecting speace would be less than 4 which may be hard to
         // avoid 3 consecutive address.
         if (PREFIX_LENGTH > 30) return randomSubAddr;