diff --git a/apps/t3/src/main/java/org/onosproject/t3/impl/Subnet.java b/apps/t3/src/main/java/org/onosproject/t3/impl/Subnet.java
new file mode 100644
index 0000000..ac5a741
--- /dev/null
+++ b/apps/t3/src/main/java/org/onosproject/t3/impl/Subnet.java
@@ -0,0 +1,133 @@
+/*
+ * Copyright 2017-present Open Networking Foundation
+ *
+ * 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 org.onosproject.t3.impl;
+
+import java.math.BigInteger;
+import java.net.InetAddress;
+import java.net.UnknownHostException;
+
+/**
+ * Utility class to test if an Ip is in a given subnet.
+ */
+public class Subnet {
+    private final int bytesSubnetCount;
+    private final BigInteger bigMask;
+    private final BigInteger bigSubnetMasked;
+
+    /**
+     * Constructor for use via format "192.168.0.0/24" or "2001:db8:85a3:880:0:0:0:0/57".
+     * @param subnetAddress the address
+     * @param bits the mask
+     */
+    public Subnet(InetAddress subnetAddress, int bits) {
+        bytesSubnetCount = subnetAddress.getAddress().length; // 4 or 16
+        bigMask = BigInteger.valueOf(-1).shiftLeft(bytesSubnetCount * 8 - bits); // mask = -1 << 32 - bits
+        bigSubnetMasked = new BigInteger(subnetAddress.getAddress()).and(bigMask);
+    }
+
+    /**
+     * Constructor for use via format "192.168.0.0/255.255.255.0" or single address.
+     * @param subnetAddress the address
+     * @param mask the mask
+     */
+    public Subnet(InetAddress subnetAddress, InetAddress mask) {
+        bytesSubnetCount = subnetAddress.getAddress().length;
+        // no mask given case is handled here.
+        bigMask = null == mask ? BigInteger.valueOf(-1) : new BigInteger(mask.getAddress());
+        bigSubnetMasked = new BigInteger(subnetAddress.getAddress()).and(bigMask);
+    }
+
+    /**
+     * Subnet factory method.
+     *
+     * @param subnetMask format: "192.168.0.0/24" or "192.168.0.0/255.255.255.0"
+     *                   or single address or "2001:db8:85a3:880:0:0:0:0/57"
+     * @return a new instance
+     * @throws UnknownHostException thrown if unsupported subnet mask.
+     */
+    public static Subnet createInstance(String subnetMask)
+            throws UnknownHostException {
+        final String[] stringArr = subnetMask.split("/");
+        if (2 > stringArr.length) {
+            return new Subnet(InetAddress.getByName(stringArr[0]), (InetAddress) null);
+        } else if (stringArr[1].contains(".") || stringArr[1].contains(":")) {
+            return new Subnet(InetAddress.getByName(stringArr[0]), InetAddress.getByName(stringArr[1]));
+        } else {
+            return new Subnet(InetAddress.getByName(stringArr[0]), Integer.parseInt(stringArr[1]));
+        }
+    }
+
+    /**
+     * Tests if the address is in the given subnet.
+     * @param address the address to test.
+     * @return true if inside the subnet
+     */
+    public boolean isInSubnet(InetAddress address) {
+        byte[] bytesAddress = address.getAddress();
+        if (this.bytesSubnetCount != bytesAddress.length) {
+            return false;
+        }
+        BigInteger bigAddress = new BigInteger(bytesAddress);
+        return bigAddress.and(this.bigMask).equals(this.bigSubnetMasked);
+    }
+
+    @Override
+    public final boolean equals(Object obj) {
+        if (!(obj instanceof Subnet)) {
+            return false;
+        }
+        final Subnet other = (Subnet) obj;
+        return bigSubnetMasked.equals(other.bigSubnetMasked) &&
+                bigMask.equals(other.bigMask) &&
+                bytesSubnetCount == other.bytesSubnetCount;
+    }
+
+    @Override
+    public final int hashCode() {
+        return bytesSubnetCount;
+    }
+
+    @Override
+    public String toString() {
+        final StringBuilder buf = new StringBuilder();
+        bigInteger2IpString(buf, bigSubnetMasked, bytesSubnetCount);
+        buf.append('/');
+        bigInteger2IpString(buf, bigMask, bytesSubnetCount);
+        return buf.toString();
+    }
+
+    private void bigInteger2IpString(StringBuilder buf, BigInteger bigInteger, int displayBytes) {
+        boolean isIPv4 = 4 == displayBytes;
+        byte[] bytes = bigInteger.toByteArray();
+        int diffLen = displayBytes - bytes.length;
+        byte fillByte = 0 > (int) bytes[0] ? (byte) 0xFF : (byte) 0x00;
+
+        int integer;
+        for (int i = 0; i < displayBytes; i++) {
+            if (0 < i && !isIPv4 && i % 2 == 0) {
+                buf.append(':');
+            } else if (0 < i && isIPv4) {
+                buf.append('.');
+            }
+            integer = 0xFF & (i < diffLen ? fillByte : bytes[i - diffLen]);
+            if (!isIPv4 && 0x10 > integer) {
+                buf.append('0');
+            }
+            buf.append(isIPv4 ? integer : Integer.toHexString(integer));
+        }
+    }
+}