diff --git a/src/test/dhcp/dhcpTest.py b/src/test/dhcp/dhcpTest.py
index 76416de..a8d7c7f 100644
--- a/src/test/dhcp/dhcpTest.py
+++ b/src/test/dhcp/dhcpTest.py
@@ -242,13 +242,159 @@
 	if cip == self.dhcp.seed_ip:
 		log.info('Got dhcp client IP %s from server %s for mac %s as desired .' %  
 		  (cip, sip, mac) )
+		assert_equal(cip, self.dhcp.seed_ip) #Negative Test Case
+
 	elif cip != self.dhcp.seed_ip:
 		log.info('Got dhcp client IP %s from server %s for mac %s .' %  
 		  (cip, sip, mac) )
 		log.info('The desired ip was: %s .' % self.dhcp.seed_ip)
-		assert_equal(cip, self.dhcp.seed_ip)
+		assert_not_equal(cip, self.dhcp.seed_ip)
+
 	elif cip == None:
 		log.info('Got DHCP NAK')
 	
 			
+    def test_dhcp_server_nak_packet(self, iface = 'veth0'):
+	''' Client sends DHCP Request for ip that is different from DHCP offer packet.'''
+	config = {'startip':'20.20.20.30', 'endip':'20.20.20.69', 
+                 'ip':'20.20.20.2', 'mac': "ca:fe:ca:fe:ca:fe",
+                 'subnet': '255.255.255.0', 'broadcast':'20.20.20.255', 'router':'20.20.20.1'}
+        self.onos_dhcp_table_load(config)
+        self.dhcp = DHCPTest(seed_ip = '20.20.20.45', iface = iface)
+	cip, sip, mac = self.dhcp.only_discover()
+	log.info('Got dhcp client IP %s from server %s for mac %s .' %  
+		  (cip, sip, mac) )
+	
+	log.info("Verifying Client 's IP and mac in DHCP Offer packet. Those should not be none, which is expected.")
+	if (cip == None and mac != None):
+		log.info("Verified that Client 's IP and mac in DHCP Offer packet are none, which is not expected behavior.")
+		assert_not_equal(cip, None)
+	else:
+		new_cip, new_sip = self.dhcp.only_request('20.20.20.31', mac)
+		if new_cip == None:
+			
+			log.info("Got DHCP server NAK.")
+			assert_equal(new_cip, None)  #Negative Test Case
+		
+	
+    def test_dhcp_lease_packet(self, iface = 'veth0'):
+	''' Client sends DHCP Discover packet for particular lease time.'''
+	config = {'startip':'20.20.20.30', 'endip':'20.20.20.69', 
+                 'ip':'20.20.20.2', 'mac': "ca:fe:ca:fe:ca:fe",
+                 'subnet': '255.255.255.0', 'broadcast':'20.20.20.255', 'router':'20.20.20.1'}
+        self.onos_dhcp_table_load(config)
+        self.dhcp = DHCPTest(seed_ip = '20.20.20.45', iface = iface)
+	log.info('Sending DHCP discover with lease time of 700')
+	cip, sip, mac, lval = self.dhcp.only_discover(lease_time = True)
+
+	log.info("Verifying Client 's IP and mac in DHCP Offer packet. Those should not be none, which is expected.")
+	if (cip == None and mac != None):
+		log.info("Verified that Client 's IP and mac in DHCP Offer packet are none, which is not expected behavior.")
+		assert_not_equal(cip, None)
+	elif lval != 700:
+		log.info('Getting dhcp client IP %s from server %s for mac %s with lease time %s. That is not 700.' %  
+		 	 (cip, sip, mac, lval) )
+		assert_not_equal(lval, 700)
+
+    def test_dhcp_client_request_after_reboot(self, iface = 'veth0'):
+	#''' Client sends DHCP Request after reboot.'''
+	
+	config = {'startip':'20.20.20.30', 'endip':'20.20.20.69', 
+                 'ip':'20.20.20.2', 'mac': "ca:fe:ca:fe:ca:fe",
+                 'subnet': '255.255.255.0', 'broadcast':'20.20.20.255', 'router':'20.20.20.1'}
+        self.onos_dhcp_table_load(config)
+        self.dhcp = DHCPTest(seed_ip = '20.20.20.45', iface = iface)
+	cip, sip, mac = self.dhcp.only_discover()
+	log.info('Got dhcp client IP %s from server %s for mac %s .' %  
+		  (cip, sip, mac) )
+	
+	log.info("Verifying Client 's IP and mac in DHCP Offer packet. Those should not be none, which is expected.")
+	
+	if (cip == None and mac != None):
+		log.info("Verified that Client 's IP and mac in DHCP Offer packet are none, which is not expected behavior.")
+		assert_not_equal(cip, None)
+		
+	else:
+		new_cip, new_sip = self.dhcp.only_request(cip, mac)
+		if new_cip == None:
+			log.info("Got DHCP server NAK.")
+		os.system('ifconfig '+iface+' down')
+		log.info('Client goes down.')
+		log.info('Delay for 5 seconds.')
+		
+		time.sleep(5)
+		
+		os.system('ifconfig '+iface+' up')
+		log.info('Client is up now.')
+		
+		new_cip, new_sip = self.dhcp.only_request(cip, mac)
+		if new_cip == None:
+			log.info("Got DHCP server NAK.")
+			assert_not_equal(new_cip, None)
+		elif new_cip != None:
+			log.info("Got DHCP ACK.")
+    
+	
+     
+    def test_dhcp_server_after_reboot(self, iface = 'veth0'):
+	''' DHCP server goes down.'''
+	config = {'startip':'20.20.20.30', 'endip':'20.20.20.69', 
+                 'ip':'20.20.20.2', 'mac': "ca:fe:ca:fe:ca:fe",
+                 'subnet': '255.255.255.0', 'broadcast':'20.20.20.255', 'router':'20.20.20.1'}
+        self.onos_dhcp_table_load(config)
+        self.dhcp = DHCPTest(seed_ip = '20.20.20.45', iface = iface)
+	cip, sip, mac = self.dhcp.only_discover()
+	log.info('Got dhcp client IP %s from server %s for mac %s .' %  
+		  (cip, sip, mac) )
+	
+	log.info("Verifying Client 's IP and mac in DHCP Offer packet. Those should not be none, which is expected.")
+	
+	if (cip == None and mac != None):
+		log.info("Verified that Client 's IP and mac in DHCP Offer packet are none, which is not expected behavior.")
+		assert_not_equal(cip, None)
+		
+	else:
+		new_cip, new_sip = self.dhcp.only_request(cip, mac)
+		if new_cip == None:
+			log.info("Got DHCP server NAK.")
+			assert_not_equal(new_cip, None)
+		log.info('Getting DHCP server Down.')
+        	
+		self.onos_ctrl.deactivate()
+
+		for i in range (0,4):
+			log.info('Checking DHCP request')
+			log.info('')
+
+			cip, sip = self.dhcp.only_request(new_cip, mac)
+
+			if cip == None and sip == None:
+				log.info('')
+				log.info('DHCP request timed out. DHCP server is down')
+			elif cip != None:
+				break
+		
+		log.info('Getting DHCP server Up.')
+        
+		status, _ = self.onos_ctrl.activate()
+        	assert_equal(status, True)
+        	time.sleep(3)
+		
+		log.info('DHCP server is Up.')
+
+		for i in range (0,4):
+			log.info('Checking DHCP request')
+			log.info('')
+
+			cip, sip, mac = self.dhcp.only_discover()
+
+			if cip == None and sip == None and mac == None:
+				log.info('')
+				log.info('DHCP request timed out.')
+			elif cip != None:
+				log.info('Got reply from DHCP server. DHCP server is down')
+				break
+
+	
+ 
 
diff --git a/src/test/utils/DHCP.py b/src/test/utils/DHCP.py
index 6c151ca..500c918 100644
--- a/src/test/utils/DHCP.py
+++ b/src/test/utils/DHCP.py
@@ -27,7 +27,7 @@
                 self.seed_ip = self.incIP(self.seed_ip)
                 self.seed_mac = self.ipToMac(self.seed_ip)
                 mac = self.seed_mac
-                
+
         chmac = self.macToChaddr(mac)
 	self.bootpmac = chmac
         L2 = Ether(dst="ff:ff:ff:ff:ff:ff", src=mac)
@@ -53,61 +53,86 @@
                 subnet_mask = val
             elif(op == 'server_id'):
                 server_id = val
-            
+
         L5 = BOOTP(chaddr=chmac, yiaddr=srcIP)
-        L6 = DHCP(options=[("message-type","request"), ("server_id",server_id), 
+        L6 = DHCP(options=[("message-type","request"), ("server_id",server_id),
                            ("subnet_mask",subnet_mask), ("requested_addr",srcIP), "end"])
         srp(L2/L3/L4/L5/L6, filter="udp and port 68", timeout=10, iface=self.iface)
         self.mac_map[mac] = (srcIP, serverIP)
         self.mac_inverse_map[srcIP] = (mac, serverIP)
         return (srcIP, serverIP)
 
-    def only_discover(self, mac = None, desired = False):  
+    def only_discover(self, mac = None, desired = False, lease_time = False):  
         '''Send a DHCP discover'''
 
         if mac is None:
             mac = self.seed_mac
 
         chmac = self.macToChaddr(mac)
+	self.bootpmac = chmac
         L2 = Ether(dst="ff:ff:ff:ff:ff:ff", src=mac)
         L3 = IP(src="0.0.0.0", dst="255.255.255.255")
         L4 = UDP(sport=68, dport=67)
-        L5 = BOOTP(ciaddr=self.seed_ip, chaddr=chmac)
+        L5 = BOOTP(chaddr=chmac)
 	if desired:
 		L6 = DHCP(options=[("message-type","discover"),("requested_addr",self.seed_ip),"end"])
-	else:
+	
+	elif time:
+		L6 = DHCP(options=[("message-type","discover"),("lease_time",700),"end"])
+		
+	elif lease_time:
         	L6 = DHCP(options=[("message-type","discover"),"end"])
 
-        resp = srp1(L2/L3/L4/L5/L6, filter="udp and port 68", timeout=10, iface=self.iface)
-	
-	if(resp.lastlayer().options [0][1] == 2):
-        	try:
-            		srcIP = resp.yiaddr
-            		serverIP = resp.siaddr
-        	except AttributeError:
-           		 print "In Attribute error."
-            		 print("Failed to acquire IP via DHCP for %s on interface %s" %(mac, self.iface))
-            		 return (None, None, None)
-		return (srcIP, serverIP, mac)
-	
-	elif(resp.lastlayer().options [0][1] == 5):
 		
-		return (None, None, None)
+
+        resp = srp1(L2/L3/L4/L5/L6, filter="udp and port 68", timeout=10, iface=self.iface)
+	if resp == None:
+        	return (None, None, None)
+		
+	self.dhcpresp = resp
+        for x in resp.lastlayer().options:
+            if(x == 'end'):
+                break
+            op,val = x
+            if(op == "message-type"):
+            	
+	    	if(val == 2):
+		
+			try:
+            			srcIP = resp.yiaddr
+            			serverIP = resp.siaddr
+        		except AttributeError:
+           			print "In Attribute error."
+            		 	print("Failed to acquire IP via DHCP for %s on interface %s" %(mac, self.iface))
+            		 	return (None, None, None)
+			
+			if lease_time == True:
+				for x in resp.lastlayer().options:
+            				if(x == 'end'):
+                				break
+            				op,val = x
+            				if(op == "lease_time"):
+						return (srcIP, serverIP, mac, val)
+			else:
+				return (srcIP, serverIP, mac)
+	
+		elif(val == 6):
+		
+			return (None, None, mac)
 
 	
     def only_request(self, cip, mac):
         '''Send a DHCP offer'''
         
-	
 	subnet_mask = "0.0.0.0"
         for x in self.dhcpresp.lastlayer().options:
-            if(x == 'end'):
-                break
-            op,val = x
-            if(op == "subnet_mask"):
-                subnet_mask = val
-            elif(op == 'server_id'):
-                server_id = val
+            	if(x == 'end'):
+                	break
+            	op,val = x
+            	if(op == "subnet_mask"):
+                	subnet_mask = val
+            	elif(op == 'server_id'):
+                	server_id = val
 
         L2 = Ether(dst="ff:ff:ff:ff:ff:ff", src=mac)
         L3 = IP(src="0.0.0.0", dst="255.255.255.255")
@@ -116,18 +141,34 @@
         L6 = DHCP(options=[("message-type","request"), ("server_id",server_id),
                            ("subnet_mask",subnet_mask), ("requested_addr",cip), "end"])
 	resp=srp1(L2/L3/L4/L5/L6, filter="udp and port 68", timeout=10, iface=self.iface)
-	if(resp.lastlayer().options [0][1] == 5):
-        	try:
-            		srcIP = resp.yiaddr
-            		serverIP = resp.siaddr
-        	except AttributeError:
-           		 print "In Attribute error."
-            		 print("Failed to acquire IP via DHCP for %s on interface %s" %(mac, self.iface))
-            		 return (None, None)
-		return (srcIP, serverIP)
-	else:
-		return (None, None)
+	if resp == None:
+        	return (None, None)
+        
+	for x in resp.lastlayer().options:
+            	if(x == 'end'):
+                	break
+            	op,val = x
+            	if(op == "message-type"):
+	
+			if(val == 5):
+        	
+				try:
+            				srcIP = resp.yiaddr
+            				serverIP = resp.siaddr
+        			except AttributeError:
+           				print "In Attribute error."
+            				print("Failed to acquire IP via DHCP for %s on interface %s" %(mac, self.iface))
+            				return (None, None)
+	        		self.mac_map[mac] = (srcIP, serverIP)
+        			self.mac_inverse_map[srcIP] = (mac, serverIP)
 
+				return (srcIP, serverIP)
+	
+			elif(val == 6):
+		
+				return (None, None)
+	
+		
 
     def discover_next(self):
         '''Send next dhcp discover/request with updated mac'''
@@ -185,14 +226,14 @@
     def incIP(self, ip, n=1):
         '''Increment an IP'''
 
-        if n < 1: 
+        if n < 1:
             return ip
         o = ip.split(".")
         for ii in range(3,-1,-1):
             if int(o[ii]) < 255:
                 o[ii] = str(int(o[ii]) + 1)
                 break
-            else: 
+            else:
                 o[ii] = str(0)
 
         n -= 1