diff --git a/src/main/java/net/onrc/onos/graph/GraphDBConnection.java b/src/main/java/net/onrc/onos/graph/GraphDBConnection.java
index 232deed..bf30297 100644
--- a/src/main/java/net/onrc/onos/graph/GraphDBConnection.java
+++ b/src/main/java/net/onrc/onos/graph/GraphDBConnection.java
@@ -7,7 +7,6 @@
 
 import com.thinkaurelius.titan.core.TitanFactory;
 import com.thinkaurelius.titan.core.TitanGraph;
-import com.thinkaurelius.titan.diskstorage.StorageException;
 import com.tinkerpop.blueprints.TransactionalGraph;
 import com.tinkerpop.blueprints.Vertex;
 import com.tinkerpop.blueprints.util.wrappers.event.EventTransactionalGraph;
@@ -82,6 +81,9 @@
 			if (!s.contains("switch_state")) {
 				graph.createKeyIndex("switch_state", Vertex.class);
 			}
+			if (!s.contains("ipv4_address")) {
+				graph.createKeyIndex("ipv4_address", Vertex.class);
+			}
 			graph.commit();
 			eg = new EventTransactionalGraph<TitanGraph>(graph);
 		}
diff --git a/src/main/java/net/onrc/onos/graph/GraphDBOperation.java b/src/main/java/net/onrc/onos/graph/GraphDBOperation.java
index f1e9b46..489eb5e 100644
--- a/src/main/java/net/onrc/onos/graph/GraphDBOperation.java
+++ b/src/main/java/net/onrc/onos/graph/GraphDBOperation.java
@@ -1,11 +1,14 @@
 package net.onrc.onos.graph;
 
 import java.util.ArrayList;
+import java.util.Iterator;
 import java.util.List;
 
+import net.onrc.onos.ofcontroller.core.INetMapTopologyObjects.IBaseObject;
 import net.onrc.onos.ofcontroller.core.INetMapTopologyObjects.IDeviceObject;
 import net.onrc.onos.ofcontroller.core.INetMapTopologyObjects.IFlowEntry;
 import net.onrc.onos.ofcontroller.core.INetMapTopologyObjects.IFlowPath;
+import net.onrc.onos.ofcontroller.core.INetMapTopologyObjects.IIpv4Address;
 import net.onrc.onos.ofcontroller.core.INetMapTopologyObjects.IPortObject;
 import net.onrc.onos.ofcontroller.core.INetMapTopologyObjects.ISwitchObject;
 import net.onrc.onos.ofcontroller.core.ISwitchStorage.SwitchState;
@@ -225,6 +228,44 @@
 		FramedGraph<TitanGraph> fg = conn.getFramedGraph();	
 		if (fg != null) fg.removeVertex(dev.asVertex());		
 	}
+	
+	public IIpv4Address newIpv4Address() {
+		return newVertex("ipv4Address", IIpv4Address.class);
+	}
+	
+	private <T extends IBaseObject> T newVertex(String type, Class<T> vertexType) {
+		FramedGraph<TitanGraph> fg = conn.getFramedGraph();
+		T newVertex = fg.addVertex(null, vertexType);
+		if (newVertex != null) {
+			newVertex.setType(type);
+		}
+		return newVertex;
+	}
+	
+	public IIpv4Address searchIpv4Address(int intIpv4Address) {
+		return searchForVertex("ipv4_address", intIpv4Address, IIpv4Address.class);
+	}
+	
+	private <T> T searchForVertex(String propertyName, Object propertyValue, Class<T> vertexType) {
+		FramedGraph<TitanGraph> fg = conn.getFramedGraph();
+		if (fg != null) {
+			Iterator<T> it = 
+					fg.getVertices(propertyName, propertyValue, vertexType).iterator();
+			if (it.hasNext()) {
+				return it.next();
+			}
+		}
+		return null;
+	}
+	
+	public IIpv4Address ensureIpv4Address(int intIpv4Address) {
+		IIpv4Address ipv4Vertex = searchIpv4Address(intIpv4Address);
+		if (ipv4Vertex == null) {
+			ipv4Vertex = newIpv4Address();
+			ipv4Vertex.setIpv4Address(intIpv4Address);
+		}
+		return ipv4Vertex;
+	}
 
 	/**
 	 * Create and return a flow path object.
diff --git a/src/main/java/net/onrc/onos/ofcontroller/core/IDeviceStorage.java b/src/main/java/net/onrc/onos/ofcontroller/core/IDeviceStorage.java
index 7310d8c..be495b9 100644
--- a/src/main/java/net/onrc/onos/ofcontroller/core/IDeviceStorage.java
+++ b/src/main/java/net/onrc/onos/ofcontroller/core/IDeviceStorage.java
@@ -9,7 +9,7 @@
 	public IDeviceObject updateDevice(IDevice device);
 	public void removeDevice(IDevice device);
 	public IDeviceObject getDeviceByMac(String mac);
-	public IDeviceObject getDeviceByIP(String ip);
+	public IDeviceObject getDeviceByIP(int ipv4Address);
 	public void changeDeviceAttachments(IDevice device);
 	public void changeDeviceIPv4Address(IDevice device);	
 }
diff --git a/src/main/java/net/onrc/onos/ofcontroller/core/INetMapTopologyObjects.java b/src/main/java/net/onrc/onos/ofcontroller/core/INetMapTopologyObjects.java
index 7b38fef..b54f6b9 100644
--- a/src/main/java/net/onrc/onos/ofcontroller/core/INetMapTopologyObjects.java
+++ b/src/main/java/net/onrc/onos/ofcontroller/core/INetMapTopologyObjects.java
@@ -149,12 +149,6 @@
 		@Property("dl_addr")
 		public void setMACAddress(String macaddr);
 		
-		@JsonProperty("ipv4")
-		@Property("nw_addr")
-		public String getIPAddress();
-		@Property("nw_addr")
-		public void setIPAddress(String ipaddr);
-		
 		@JsonIgnore
 		@Adjacency(label="host",direction = Direction.IN)
 		public Iterable<IPortObject> getAttachedPorts();
@@ -171,6 +165,23 @@
 		@GremlinGroovy("it.in('host').in('on')")
 		public Iterable<ISwitchObject> getSwitch();
 		
+		//
+		// IPv4 Addresses
+		//
+		@JsonProperty("ipv4addresses")
+		@Adjacency(label="hasAddress")
+		public Iterable<IIpv4Address> getIpv4Addresses();
+
+		@JsonIgnore
+		@GremlinGroovy("it.out('hasAddress').has('ipv4', ipv4Address)")
+		public IIpv4Address getIpv4Address(@GremlinParam("ipv4Address") final int ipv4Address);
+		
+		@Adjacency(label="hasAddress")
+		public void addIpv4Address(final IIpv4Address ipv4Address);
+		
+		@Adjacency(label="hasAddress")
+		public void removeIpv4Address(final IIpv4Address ipv4Address);
+		
 /*		@JsonProperty("dpid")
 		@GremlinGroovy("_().in('host').in('on').next().getProperty('dpid')")
 		public Iterable<String> getSwitchDPID();
@@ -183,7 +194,21 @@
 		@GremlinGroovy("_().in('host').in('on').path(){it.number}{it.dpid}")
 		public Iterable<SwitchPort> getAttachmentPoints();*/
 	}
-
+		
+	public interface IIpv4Address extends IBaseObject {
+		
+		@JsonProperty("ipv4")
+		@Property("ipv4_address")
+		public int getIpv4Address();
+		
+		@Property("ipv4_address")
+		public void setIpv4Address(int ipv4Address);
+		
+		@JsonIgnore
+		@GremlinGroovy("it.in('hasAddress')")
+		public IDeviceObject getDevice();
+	}
+	
 public interface IFlowPath extends IBaseObject {
 		@JsonProperty("flowId")
 		@Property("flow_id")
diff --git a/src/main/java/net/onrc/onos/ofcontroller/core/internal/DeviceStorageImpl.java b/src/main/java/net/onrc/onos/ofcontroller/core/internal/DeviceStorageImpl.java
index 63eaacb..256008a 100644
--- a/src/main/java/net/onrc/onos/ofcontroller/core/internal/DeviceStorageImpl.java
+++ b/src/main/java/net/onrc/onos/ofcontroller/core/internal/DeviceStorageImpl.java
@@ -1,30 +1,31 @@
 package net.onrc.onos.ofcontroller.core.internal;
 
-import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.List;
+
+import net.floodlightcontroller.devicemanager.IDevice;
+import net.floodlightcontroller.devicemanager.SwitchPort;
+import net.onrc.onos.graph.GraphDBOperation;
+import net.onrc.onos.ofcontroller.core.IDeviceStorage;
+import net.onrc.onos.ofcontroller.core.INetMapTopologyObjects.IDeviceObject;
+import net.onrc.onos.ofcontroller.core.INetMapTopologyObjects.IIpv4Address;
+import net.onrc.onos.ofcontroller.core.INetMapTopologyObjects.IPortObject;
+
 import org.openflow.util.HexString;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import com.google.common.collect.Lists;
 import com.thinkaurelius.titan.core.TitanException;
-import net.floodlightcontroller.devicemanager.IDevice;
-import net.floodlightcontroller.devicemanager.SwitchPort;
-import net.floodlightcontroller.packet.IPv4;
-import net.onrc.onos.graph.GraphDBOperation;
-import net.onrc.onos.ofcontroller.core.IDeviceStorage;
-import net.onrc.onos.ofcontroller.core.INetMapTopologyObjects.IDeviceObject;
-import net.onrc.onos.ofcontroller.core.INetMapTopologyObjects.IPortObject;
-import net.onrc.onos.ofcontroller.core.internal.SwitchStorageImpl;
 
 /**
  * This is the class for storing the information of devices into CassandraDB
  * @author Pankaj
  */
 public class DeviceStorageImpl implements IDeviceStorage {
+	protected final static Logger log = LoggerFactory.getLogger(SwitchStorageImpl.class);
 	
 	private GraphDBOperation ope;
-	protected final static Logger log = LoggerFactory.getLogger(SwitchStorageImpl.class);
 
 	/***
 	 * Initialize function. Before you use this class, please call this method
@@ -32,10 +33,10 @@
 	 */
 	@Override
 	public void init(String conf) {
-		try{
+		try {
 			ope = new GraphDBOperation(conf);
-		} catch(Exception e) {
-			log.error(e.getMessage());
+		} catch (TitanException e) {
+			log.error("Couldn't open graph operation", e);
 		}
 	}	
 	
@@ -67,39 +68,31 @@
 		IDeviceObject obj = null;
  		try {
  			if ((obj = ope.searchDevice(device.getMACAddressString())) != null) {
- 				log.debug("Adding device {}: found existing device",device.getMACAddressString());
+ 				log.debug("Adding device {}: found existing device", device.getMACAddressString());
             } else {
             	obj = ope.newDevice();
-                log.debug("Adding device {}: creating new device",device.getMACAddressString());
+                log.debug("Adding device {}: creating new device", device.getMACAddressString());
             }
-	            changeDeviceAttachments(device, obj);
-	
-				String multiIntString = "";
-				for(Integer intValue : device.getIPv4Addresses()) {
-				   if (multiIntString == null || multiIntString.isEmpty()){
-				     multiIntString = IPv4.fromIPv4Address(intValue);
-				     multiIntString = "[" + IPv4.fromIPv4Address(intValue);
-				   }else{
-				        multiIntString += "," + IPv4.fromIPv4Address(intValue);
-				   }
-				}
-	 	            
-	            if(multiIntString.toString() != null && !multiIntString.toString().isEmpty()){
-	            	obj.setIPAddress(multiIntString + "]");
-	            }
-	            
-	 			obj.setMACAddress(device.getMACAddressString());
-	 			obj.setType("device");
-	 			obj.setState("ACTIVE");
-	 			ope.commit();
  			
-	 			log.debug("Adding device {}",device.getMACAddressString());
-		} catch (Exception e) {
+            changeDeviceAttachments(device, obj);
+	            
+            for (Integer intIpv4Address : device.getIPv4Addresses()) {
+            	obj.addIpv4Address(ope.ensureIpv4Address(intIpv4Address));
+            }
+            
+ 			obj.setMACAddress(device.getMACAddressString());
+ 			obj.setType("device");
+ 			obj.setState("ACTIVE");
+ 			ope.commit();
+		
+ 			//log.debug("Adding device {}",device.getMACAddressString());
+		} catch (TitanException e) {
 			ope.rollback();
 			log.error(":addDevice mac:{} failed", device.getMACAddressString());
 			obj = null;
-		}	
- 			return obj;		
+		}
+ 		
+		return obj;		
 	}
 
 	/***
@@ -125,7 +118,7 @@
              	ope.commit();
             	log.error("DeviceStorage:removeDevice mac:{} done", device.getMACAddressString());
             }
-		} catch (Exception e) {
+		} catch (TitanException e) {
 			ope.rollback();
 			log.error("DeviceStorage:removeDevice mac:{} failed", device.getMACAddressString());
 		}
@@ -147,23 +140,15 @@
 	 * @return IDeviceObject you want to get.
 	 */
 	@Override
-	public IDeviceObject getDeviceByIP(String ip) {
-		try
-		{
-			for(IDeviceObject dev : ope.getDevices()){
-				String ips;
-				if((ips = dev.getIPAddress()) != null){
-					String nw_addr_wob = ips.replace("[", "").replace("]", "");
-					ArrayList<String> iplists = Lists.newArrayList(nw_addr_wob.split(","));	
-					if(iplists.contains(ip)){
-						return dev;
-					}
-				}
+	public IDeviceObject getDeviceByIP(int ipv4Address) {
+		try {
+			IIpv4Address ipv4AddressVertex = ope.searchIpv4Address(ipv4Address);
+			if (ipv4AddressVertex != null) {
+				return ipv4AddressVertex.getDevice();
 			}
 			return null;
 		}
-		catch (Exception e)
-		{
+		catch (TitanException e) {
 			log.error("DeviceStorage:getDeviceByIP:{} failed");
 			return null;
 		}
@@ -178,14 +163,14 @@
 		IDeviceObject obj = null;
  		try {
             if ((obj = ope.searchDevice(device.getMACAddressString())) != null) {
-                log.debug("Changing device ports {}: found existing device",device.getMACAddressString());
+                log.debug("Changing device ports {}: found existing device", device.getMACAddressString());
                 changeDeviceAttachments(device, obj);
                 ope.commit();
             } else {
-   				log.debug("failed to search device...now adding {}",device.getMACAddressString());
+   				log.debug("failed to search device...now adding {}", device.getMACAddressString());
    				addDevice(device);
-            }            			
-		} catch (Exception e) {
+            }
+		} catch (TitanException e) {
 			ope.rollback();
 			log.error(":addDevice mac:{} failed", device.getMACAddressString());
 		}	
@@ -199,33 +184,33 @@
 	public void changeDeviceAttachments(IDevice device, IDeviceObject obj) {
 		SwitchPort[] attachmentPoints = device.getAttachmentPoints();
 		List<IPortObject> attachedPorts = Lists.newArrayList(obj.getAttachedPorts());
-		
-        for (SwitchPort ap : attachmentPoints) {
-        	//Check weather there is the port
-          	 IPortObject port = ope.searchPort( HexString.toHexString(ap.getSwitchDPID()),
-												(short) ap.getPort());
-          	 log.debug("New Switch Port is {},{}", HexString.toHexString(ap.getSwitchDPID()),(short) ap.getPort());
-	       	 
-	       	 if(port != null){
-	   			if(attachedPorts.contains(port))
-	       		{
-		       		log.debug("This is the port you already attached {}: do nothing",device.getMACAddressString());
-		       		//This port will be remained, so remove from the removed port lists.
-		       		attachedPorts.remove(port);
-		       	} else {
-	     		   log.debug("Adding device {}: attaching to port",device.getMACAddressString());
-		       		port.setDevice(obj);  
-		        }
-	    	
-		       	log.debug("port number is {}", port.getNumber().toString());
-		        log.debug("port desc is {}", port.getDesc());  
-	       	 }
-        }      		 
-	            
-	    for (IPortObject port: attachedPorts) {
-            log.debug("Detouching the device {}: detouching from port",device.getMACAddressString());
-       		port.removeDevice(obj);
-        }
+
+		for (SwitchPort ap : attachmentPoints) {
+			//Check if there is the port
+			IPortObject port = ope.searchPort(HexString.toHexString(ap.getSwitchDPID()),
+					(short) ap.getPort());
+			log.debug("New Switch Port is {},{}", 
+					HexString.toHexString(ap.getSwitchDPID()), (short) ap.getPort());
+
+			if (port != null){
+				if (attachedPorts.contains(port)) {
+					log.debug("This is the port you already attached {}: do nothing", device.getMACAddressString());
+					//This port will be remained, so remove from the removed port lists.
+					attachedPorts.remove(port);
+				} else {
+					log.debug("Adding device {}: attaching to port", device.getMACAddressString());
+					port.setDevice(obj);  
+				}
+
+				log.debug("port number is {}", port.getNumber().toString());
+				log.debug("port desc is {}", port.getDesc());  
+			}
+		}      		 
+
+		for (IPortObject port: attachedPorts) {
+			log.debug("Detaching the device {}: detaching from port", device.getMACAddressString());
+			port.removeDevice(obj);
+		}
 	}
 
 	/***
@@ -234,22 +219,24 @@
 	 */
 	@Override
 	public void changeDeviceIPv4Address(IDevice device) {
+		log.debug("Changing IP address for {} to {}", device.getMACAddressString(),
+				device.getIPv4Addresses());
 		IDeviceObject obj;
   		try {
   			if ((obj = ope.searchDevice(device.getMACAddressString())) != null) {
-
-  				String multiIntString = "";
-  				for(Integer intValue : device.getIPv4Addresses()){
-  				   if (multiIntString == null || multiIntString.isEmpty()){
-  				     multiIntString = "[" + IPv4.fromIPv4Address(intValue);
-  				   } else {
-  				        multiIntString += "," + IPv4.fromIPv4Address(intValue);
-  				   }
+  				for (int ipv4Address : device.getIPv4Addresses()) {
+  					if (obj.getIpv4Address(ipv4Address) == null) {
+  						IIpv4Address dbIpv4Address = ope.ensureIpv4Address(ipv4Address);
+  						obj.addIpv4Address(dbIpv4Address);
+  					}
   				}
   				
-  	            if(multiIntString != null && !multiIntString.isEmpty()){
-  	            	obj.setIPAddress(multiIntString + "]");
-  	            }
+  				List<Integer> deviceIpv4Addresses = Arrays.asList(device.getIPv4Addresses());
+  				for (IIpv4Address dbIpv4Address : obj.getIpv4Addresses()) {
+  					if (!deviceIpv4Addresses.contains(dbIpv4Address.getIpv4Address())) {
+  						obj.removeIpv4Address(dbIpv4Address);
+  					}
+  				}
   	            
               	ope.commit();
   			} else {
@@ -257,7 +244,7 @@
             }		
   		} catch (TitanException e) {
   			ope.rollback();
-			log.error(":changeDeviceIPv4Address mac:{} failed due to exception {}", device.getMACAddressString(),e);
+			log.error(":changeDeviceIPv4Address mac:{} failed due to exception {}", device.getMACAddressString(), e);
 		}
 	}
 
diff --git a/src/main/java/net/onrc/onos/ofcontroller/core/internal/SwitchStorageImpl.java b/src/main/java/net/onrc/onos/ofcontroller/core/internal/SwitchStorageImpl.java
index 26d4e40..8d93acf 100644
--- a/src/main/java/net/onrc/onos/ofcontroller/core/internal/SwitchStorageImpl.java
+++ b/src/main/java/net/onrc/onos/ofcontroller/core/internal/SwitchStorageImpl.java
@@ -333,6 +333,11 @@
         }
 	}
 
+	// TODO There's an issue here where a port with that ID could already
+	// exist when we try to add this one (because it's left over from an
+	// old topology). We need to remove an old port with the same ID when
+	// we add the new port. Also it seems that old ports like this are 
+	// never cleaned up and will remain in the DB in the ACTIVE state forever.
 	private IPortObject addPortImpl(ISwitchObject sw, short portNum) {
 		IPortObject p = op.newPort(sw.getDPID(), portNum);
 		p.setState("ACTIVE");
diff --git a/src/main/java/net/onrc/onos/ofcontroller/proxyarp/ProxyArpManager.java b/src/main/java/net/onrc/onos/ofcontroller/proxyarp/ProxyArpManager.java
index a745aaf..a5dabc9 100644
--- a/src/main/java/net/onrc/onos/ofcontroller/proxyarp/ProxyArpManager.java
+++ b/src/main/java/net/onrc/onos/ofcontroller/proxyarp/ProxyArpManager.java
@@ -17,7 +17,6 @@
 import net.floodlightcontroller.core.IFloodlightProviderService;
 import net.floodlightcontroller.core.IOFMessageListener;
 import net.floodlightcontroller.core.IOFSwitch;
-import net.floodlightcontroller.devicemanager.IDevice;
 import net.floodlightcontroller.devicemanager.IDeviceService;
 import net.floodlightcontroller.packet.ARP;
 import net.floodlightcontroller.packet.Ethernet;
@@ -26,7 +25,10 @@
 import net.floodlightcontroller.topology.ITopologyService;
 import net.floodlightcontroller.util.MACAddress;
 import net.onrc.onos.ofcontroller.bgproute.Interface;
+import net.onrc.onos.ofcontroller.core.IDeviceStorage;
+import net.onrc.onos.ofcontroller.core.INetMapTopologyObjects.IDeviceObject;
 import net.onrc.onos.ofcontroller.core.config.IConfigInfoService;
+import net.onrc.onos.ofcontroller.core.internal.DeviceStorageImpl;
 
 import org.openflow.protocol.OFMessage;
 import org.openflow.protocol.OFPacketIn;
@@ -57,6 +59,8 @@
 	private IConfigInfoService configService;
 	private IRestApiService restApi;
 	
+	private IDeviceStorage deviceStorage;
+	
 	private short vlan;
 	private static final short NO_VLAN = 0;
 	
@@ -141,6 +145,9 @@
 		restApi.addRestletRoutable(new ArpWebRoutable());
 		floodlightProvider.addOFMessageListener(OFType.PACKET_IN, this);
 		
+		deviceStorage = new DeviceStorageImpl();
+		deviceStorage.init("");
+		
 		Timer arpTimer = new Timer("arp-processing");
 		arpTimer.scheduleAtFixedRate(new TimerTask() {
 			@Override
@@ -285,13 +292,15 @@
 		//MACAddress macAddress = arpCache.lookup(target);
 		
 		//IDevice dstDevice = deviceService.fcStore.get(cntx, IDeviceService.CONTEXT_DST_DEVICE);
-		Iterator<? extends IDevice> it = deviceService.queryDevices(
-				null, null, InetAddresses.coerceToInteger(target), null, null);
+		//Iterator<? extends IDevice> it = deviceService.queryDevices(
+				//null, null, InetAddresses.coerceToInteger(target), null, null);
 		
-		IDevice targetDevice = null;
-		if (it.hasNext()) {
-			targetDevice = it.next();
-		}
+		//IDevice targetDevice = null;
+		//if (it.hasNext()) {
+			//targetDevice = it.next();
+		//}
+		IDeviceObject targetDevice = 
+				deviceStorage.getDeviceByIP(InetAddresses.coerceToInteger(target));
 		
 		if (targetDevice != null) {
 			//We have the device in our database, so send a reply