diff --git a/src/main/java/net/onrc/onos/ofcontroller/proxyarp/ArpCache.java b/src/main/java/net/onrc/onos/ofcontroller/proxyarp/ArpCache.java
new file mode 100644
index 0000000..8b9c65a
--- /dev/null
+++ b/src/main/java/net/onrc/onos/ofcontroller/proxyarp/ArpCache.java
@@ -0,0 +1,87 @@
+package net.onrc.onos.ofcontroller.proxyarp;
+
+import java.net.InetAddress;
+import java.util.HashMap;
+import java.util.Map;
+
+import net.floodlightcontroller.util.MACAddress;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Implements a basic ARP cache which maps IPv4 addresses to MAC addresses.
+ * Mappings time out after a short period of time (currently 1 min). We don't
+ * try and refresh the mapping before the entry times out because as a controller
+ * we don't know if the mapping is still needed.
+ *
+ */
+
+/* TODO clean out old ARP entries out of the cache periodically. We currently 
+ * don't do this which means the cache memory size will never decrease. We already
+ * have a periodic thread that can be used to do this in ProxyArpManager.
+ */
+public class ArpCache {
+	private final static Logger log = LoggerFactory.getLogger(ArpCache.class);
+	
+	private final long ARP_ENTRY_TIMEOUT = 60000; //ms (1 min)
+	
+	//Protected by locking on the ArpCache object
+	private final Map<InetAddress, ArpCacheEntry> arpCache;
+	
+	private static class ArpCacheEntry {
+		private final MACAddress macAddress;
+		private long timeLastSeen;	
+
+		public ArpCacheEntry(MACAddress macAddress) {
+			this.macAddress = macAddress;
+			this.timeLastSeen = System.currentTimeMillis();
+		}
+
+		public MACAddress getMacAddress() {
+			return macAddress;
+		}
+
+		public long getTimeLastSeen() {
+			return timeLastSeen;
+		}
+		
+		public void setTimeLastSeen(long time){
+			timeLastSeen = time;
+		}
+	}
+
+	public ArpCache() {
+		arpCache = new HashMap<InetAddress, ArpCacheEntry>();
+	}
+
+	public synchronized MACAddress lookup(InetAddress ipAddress){	
+		ArpCacheEntry arpEntry = arpCache.get(ipAddress);
+		
+		if (arpEntry == null){
+			return null;
+		}
+		
+		if (System.currentTimeMillis() - arpEntry.getTimeLastSeen() 
+				> ARP_ENTRY_TIMEOUT){
+			//Entry has timed out so we'll remove it and return null
+			log.trace("Removing expired ARP entry for {}", ipAddress.getHostAddress());
+			
+			arpCache.remove(ipAddress);
+			return null;
+		}
+		
+		return arpEntry.getMacAddress();
+	}
+
+	public synchronized void update(InetAddress ipAddress, MACAddress macAddress){
+		ArpCacheEntry arpEntry = arpCache.get(ipAddress);
+		
+		if (arpEntry != null && arpEntry.getMacAddress().equals(macAddress)){
+			arpEntry.setTimeLastSeen(System.currentTimeMillis());
+		}
+		else {
+			arpCache.put(ipAddress, new ArpCacheEntry(macAddress));
+		}
+	}
+}
diff --git a/src/main/java/net/onrc/onos/ofcontroller/proxyarp/ArpTableEntry.java b/src/main/java/net/onrc/onos/ofcontroller/proxyarp/ArpTableEntry.java
deleted file mode 100644
index 5830cfd..0000000
--- a/src/main/java/net/onrc/onos/ofcontroller/proxyarp/ArpTableEntry.java
+++ /dev/null
@@ -1,27 +0,0 @@
-package net.onrc.onos.ofcontroller.proxyarp;
-
-
-public class ArpTableEntry {
-	
-	private byte[] macAddress;
-	private long timeLastSeen;	
-
-	public ArpTableEntry(byte[] macAddress, long timeLastSeen) {
-		this.macAddress = macAddress;
-		this.timeLastSeen = timeLastSeen;
-	}
-
-	public byte[] getMacAddress() {
-		return macAddress;
-	}
-
-	public long getTimeLastSeen() {
-		return timeLastSeen;
-	}
-	
-	public void setTimeLastSeen(long time){
-		//TODO thread safety issues?
-		timeLastSeen = time;
-	}
-
-}
diff --git a/src/main/java/net/onrc/onos/ofcontroller/proxyarp/HostArpRequester.java b/src/main/java/net/onrc/onos/ofcontroller/proxyarp/HostArpRequester.java
index 1474d02..fd30574 100644
--- a/src/main/java/net/onrc/onos/ofcontroller/proxyarp/HostArpRequester.java
+++ b/src/main/java/net/onrc/onos/ofcontroller/proxyarp/HostArpRequester.java
@@ -3,6 +3,7 @@
 import java.net.InetAddress;
 
 import net.floodlightcontroller.packet.ARP;
+import net.floodlightcontroller.util.MACAddress;
 
 public class HostArpRequester implements IArpRequester {
 
@@ -21,7 +22,7 @@
 	}
 
 	@Override
-	public void arpResponse(InetAddress ipAddress, byte[] macAddress) {
+	public void arpResponse(InetAddress ipAddress, MACAddress macAddress) {
 		arpService.sendArpReply(arpRequest, dpid, port, macAddress);
 	}
 
diff --git a/src/main/java/net/onrc/onos/ofcontroller/proxyarp/IArpRequester.java b/src/main/java/net/onrc/onos/ofcontroller/proxyarp/IArpRequester.java
index 90da2ba..66a17a2 100644
--- a/src/main/java/net/onrc/onos/ofcontroller/proxyarp/IArpRequester.java
+++ b/src/main/java/net/onrc/onos/ofcontroller/proxyarp/IArpRequester.java
@@ -2,6 +2,20 @@
 
 import java.net.InetAddress;
 
+import net.floodlightcontroller.util.MACAddress;
+
+/**
+ * Callback interface for modules using the {@link IProxyArpService} to
+ * send ARP requests.
+ *
+ */
 public interface IArpRequester {
-	public void arpResponse(InetAddress ipAddress, byte[] macAddress);
+	/**
+	 * Callback method that will be called by the {@link IProxyArpService} 
+	 * when it receives a reply for a request previously submitted by this
+	 * {@code IArpRequester}.
+	 * @param ipAddress The IP address than an ARP request was sent for
+	 * @param macAddress The MAC address mapped to the requested IP address
+	 */
+	public void arpResponse(InetAddress ipAddress, MACAddress macAddress);
 }
diff --git a/src/main/java/net/onrc/onos/ofcontroller/proxyarp/IProxyArpService.java b/src/main/java/net/onrc/onos/ofcontroller/proxyarp/IProxyArpService.java
index 2bb32f4..7dde89b 100644
--- a/src/main/java/net/onrc/onos/ofcontroller/proxyarp/IProxyArpService.java
+++ b/src/main/java/net/onrc/onos/ofcontroller/proxyarp/IProxyArpService.java
@@ -3,6 +3,7 @@
 import java.net.InetAddress;
 
 import net.floodlightcontroller.packet.ARP;
+import net.floodlightcontroller.util.MACAddress;
 
 public interface IProxyArpService {
 	
@@ -16,7 +17,7 @@
 	 * @param port
 	 * @param targetMac
 	 */
-	public void sendArpReply(ARP arpRequest, long dpid, short port, byte[] targetMac);
+	public void sendArpReply(ARP arpRequest, long dpid, short port, MACAddress targetMac);
 	
 	/**
 	 * Returns the mac address if there is a valid entry in the cache.
@@ -24,7 +25,7 @@
 	 * @param ipAddress
 	 * @return
 	 */
-	public byte[] getMacAddress(InetAddress ipAddress);
+	public MACAddress getMacAddress(InetAddress ipAddress);
 	
 	/**
 	 * Tell the IProxyArpService to send an ARP request for the IP address.
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 6e12f28..fe16144 100644
--- a/src/main/java/net/onrc/onos/ofcontroller/proxyarp/ProxyArpManager.java
+++ b/src/main/java/net/onrc/onos/ofcontroller/proxyarp/ProxyArpManager.java
@@ -5,7 +5,6 @@
 import java.net.UnknownHostException;
 import java.util.ArrayList;
 import java.util.Collection;
-import java.util.HashMap;
 import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
@@ -44,21 +43,19 @@
 public class ProxyArpManager implements IProxyArpService, IOFMessageListener {
 	private final static Logger log = LoggerFactory.getLogger(ProxyArpManager.class);
 	
-	private final long ARP_ENTRY_TIMEOUT = 600000; //ms (== 10 mins)
-	
 	private final long ARP_TIMER_PERIOD = 60000; //ms (== 1 min) 
 			
-	private IFloodlightProviderService floodlightProvider;
-	private ITopologyService topology;
-	private ILayer3InfoService layer3;
+	private final IFloodlightProviderService floodlightProvider;
+	private final ITopologyService topology;
+	private final ILayer3InfoService layer3;
 	
-	private Map<InetAddress, ArpTableEntry> arpTable;
+	private final ArpCache arpCache;
 
-	private SetMultimap<InetAddress, ArpRequest> arpRequests;
+	private final SetMultimap<InetAddress, ArpRequest> arpRequests;
 	
-	private class ArpRequest {
+	private static class ArpRequest {
 		private final IArpRequester requester;
-		private boolean retry;
+		private final boolean retry;
 		private long requestTime;
 		
 		public ArpRequest(IArpRequester requester, boolean retry){
@@ -82,7 +79,7 @@
 			return retry;
 		}
 		
-		public void dispatchReply(InetAddress ipAddress, byte[] replyMacAddress) {
+		public void dispatchReply(InetAddress ipAddress, MACAddress replyMacAddress) {
 			requester.arpResponse(ipAddress, replyMacAddress);
 		}
 	}
@@ -93,7 +90,7 @@
 		this.topology = topology;
 		this.layer3 = layer3;
 		
-		arpTable = new HashMap<InetAddress, ArpTableEntry>();
+		arpCache = new ArpCache();
 
 		arpRequests = Multimaps.synchronizedSetMultimap(
 				HashMultimap.<InetAddress, ArpRequest>create());
@@ -226,16 +223,16 @@
 						target.getHostAddress(), layer3.getRouterMacAddress());
 				
 				sendArpReply(arp, sw.getId(), pi.getInPort(), 
-						layer3.getRouterMacAddress().toBytes());
+						layer3.getRouterMacAddress());
 			}
 			
 			return;
 		}
 		
-		byte[] mac = lookupArpTable(arp.getTargetProtocolAddress());
+		MACAddress macAddress = arpCache.lookup(target);
 		
-		if (mac == null){
-			//Mac address is not in our arp table.
+		if (macAddress == null){
+			//MAC address is not in our ARP cache.
 			
 			//Record where the request came from so we know where to send the reply
 			arpRequests.put(target, new ArpRequest(
@@ -249,11 +246,11 @@
 			if (log.isTraceEnabled()) {
 				log.trace("Sending reply: {} => {} to host at {}/{}", new Object [] {
 						inetAddressToString(arp.getTargetProtocolAddress()),
-						MACAddress.valueOf(mac).toString(),
+						macAddress.toString(),
 						HexString.toHexString(sw.getId()), pi.getInPort()});
 			}
 			
-			sendArpReply(arp, sw.getId(), pi.getInPort(), mac);
+			sendArpReply(arp, sw.getId(), pi.getInPort(), macAddress);
 		}
 	}
 	
@@ -265,18 +262,20 @@
 					HexString.toHexString(sw.getId()), pi.getInPort()});
 		}
 		
-		updateArpTable(arp);
-		
-		//See if anyone's waiting for this ARP reply
-		InetAddress addr;
+		InetAddress senderIpAddress;
 		try {
-			addr = InetAddress.getByAddress(arp.getSenderProtocolAddress());
+			senderIpAddress = InetAddress.getByAddress(arp.getSenderProtocolAddress());
 		} catch (UnknownHostException e) {
 			log.debug("Invalid address in ARP reply", e);
 			return;
 		}
 		
-		Set<ArpRequest> requests = arpRequests.get(addr);
+		MACAddress senderMacAddress = MACAddress.valueOf(arp.getSenderHardwareAddress());
+		
+		arpCache.update(senderIpAddress, senderMacAddress);
+		
+		//See if anyone's waiting for this ARP reply
+		Set<ArpRequest> requests = arpRequests.get(senderIpAddress);
 		
 		//Synchronize on the Multimap while using an iterator for one of the sets
 		List<ArpRequest> requestsToSend = new ArrayList<ArpRequest>(requests.size());
@@ -291,57 +290,7 @@
 		
 		//Don't hold an ARP lock while dispatching requests
 		for (ArpRequest request : requestsToSend) {
-			request.dispatchReply(addr, arp.getSenderHardwareAddress());
-		}
-	}
-
-	private synchronized byte[] lookupArpTable(byte[] ipAddress){
-		InetAddress addr;
-		try {
-			addr = InetAddress.getByAddress(ipAddress);
-		} catch (UnknownHostException e) {
-			log.debug("Unable to create InetAddress", e);
-			return null;
-		}
-		
-		ArpTableEntry arpEntry = arpTable.get(addr);
-		
-		if (arpEntry == null){
-			return null;
-		}
-		
-		if (System.currentTimeMillis() - arpEntry.getTimeLastSeen() 
-				> ARP_ENTRY_TIMEOUT){
-			//Entry has timed out so we'll remove it and return null
-			log.trace("Removing expired ARP entry for {}", 
-					inetAddressToString(ipAddress));
-			
-			arpTable.remove(addr);
-			return null;
-		}
-		
-		return arpEntry.getMacAddress();
-	}
-	
-	private synchronized void updateArpTable(ARP arp){
-		InetAddress addr;
-		try {
-			addr = InetAddress.getByAddress(arp.getSenderProtocolAddress());
-		} catch (UnknownHostException e) {
-			log.debug("Unable to create InetAddress", e);
-			return;
-		}
-		
-		ArpTableEntry arpEntry = arpTable.get(addr);
-		
-		if (arpEntry != null 
-				&& arpEntry.getMacAddress() == arp.getSenderHardwareAddress()){
-			arpEntry.setTimeLastSeen(System.currentTimeMillis());
-		}
-		else {
-			arpTable.put(addr, 
-					new ArpTableEntry(arp.getSenderHardwareAddress(), 
-										System.currentTimeMillis()));
+			request.dispatchReply(senderIpAddress, senderMacAddress);
 		}
 	}
 	
@@ -514,11 +463,12 @@
 	 * IProxyArpService methods
 	 */
 	
-	public void sendArpReply(ARP arpRequest, long dpid, short port, byte[] targetMac) {
+	@Override
+	public void sendArpReply(ARP arpRequest, long dpid, short port, MACAddress targetMac) {
 		if (log.isTraceEnabled()) {
 			log.trace("Sending reply {} => {} to {}", new Object[] {
 					inetAddressToString(arpRequest.getTargetProtocolAddress()),
-					HexString.toHexString(targetMac),
+					targetMac,
 					inetAddressToString(arpRequest.getSenderProtocolAddress())});
 		}
 		
@@ -528,14 +478,14 @@
 			.setHardwareAddressLength((byte)Ethernet.DATALAYER_ADDRESS_LENGTH)
 			.setProtocolAddressLength((byte)IPv4.ADDRESS_LENGTH)
 			.setOpCode(ARP.OP_REPLY)
-			.setSenderHardwareAddress(targetMac)
+			.setSenderHardwareAddress(targetMac.toBytes())
 			.setSenderProtocolAddress(arpRequest.getTargetProtocolAddress())
 			.setTargetHardwareAddress(arpRequest.getSenderHardwareAddress())
 			.setTargetProtocolAddress(arpRequest.getSenderProtocolAddress());
 		
 		Ethernet eth = new Ethernet();
 		eth.setDestinationMACAddress(arpRequest.getSenderHardwareAddress())
-			.setSourceMACAddress(targetMac)
+			.setSourceMACAddress(targetMac.toBytes())
 			.setEtherType(Ethernet.TYPE_ARP)
 			.setPayload(arpReply);
 		
@@ -571,8 +521,8 @@
 	}
 
 	@Override
-	public byte[] getMacAddress(InetAddress ipAddress) {
-		return lookupArpTable(ipAddress.getAddress());
+	public MACAddress getMacAddress(InetAddress ipAddress) {
+		return arpCache.lookup(ipAddress);
 	}
 
 	@Override