1 00:00:00,510 --> 00:00:07,290 Now that we've discussed address Klosters in IP version 4 we're going to continue the discussion looking 2 00:00:07,410 --> 00:00:15,840 at special addresses such as the local broadcaster trace loopback addresses and other special addresses 3 00:00:16,050 --> 00:00:18,720 that you'll encounter in IP version 4. 4 00:00:18,990 --> 00:00:25,890 We also look at network mosques and Sajda or close listening to the main routing and we'll see how that 5 00:00:26,040 --> 00:00:32,740 affects the network and host portion of addresses in IP version 4. 6 00:00:32,750 --> 00:00:39,690 So now let's look at some of the special addresses that you'll encounter in your networking Korea. 7 00:00:40,040 --> 00:00:48,020 The first one is directed broad cost address a directed broad cost address is used by hosts to send 8 00:00:48,020 --> 00:00:57,980 data to all devices on the specific subnet or specific network in direct broadcast addresses the entire 9 00:00:57,980 --> 00:01:02,680 host portion of the address is populated with binary ones. 10 00:01:02,720 --> 00:01:12,470 So as an example if we have a network of 172 docked thirty one 0.0 the directed broadcast address is 11 00:01:12,580 --> 00:01:20,650 1 7 to Dr 31 to 2 5 5 2 2 5 5 notice because this is a class be it race. 12 00:01:20,720 --> 00:01:28,460 The first two octets denotes network and the last two octets denotes host portion of the address. 13 00:01:28,640 --> 00:01:37,450 So the host portion is filled with binary ones 255 in decimal equates to eight binary ones. 14 00:01:37,520 --> 00:01:44,820 So the host portion is therefore populated with binary ones in both the third and fourth octet. 15 00:01:45,020 --> 00:01:54,470 So the address now becomes 1 7 2 or 3 1 2 2 4 5 2 2 4 5 rodders can be configured to route directed 16 00:01:54,500 --> 00:02:01,790 broadcasts but by default directed broadcasts are not routed from one physical interface to another 17 00:02:01,790 --> 00:02:06,540 physical interface or from one villain to another villain. 18 00:02:06,860 --> 00:02:15,470 They are hacking utilities that you can download and use to launch denial of service attacks or decrease 19 00:02:15,530 --> 00:02:23,180 attacks by using directed fraud costs and thus for security reasons it's recommended that the forwarding 20 00:02:23,300 --> 00:02:26,140 of directed proved costs be disabled. 21 00:02:26,150 --> 00:02:30,590 This is the default on modern versions of the Cisco IOS. 22 00:02:30,680 --> 00:02:36,680 So routers and switches will not forward directed broadcasts from one villain to another we'll run them 23 00:02:36,680 --> 00:02:38,980 from wanting to face to another interface. 24 00:02:39,380 --> 00:02:41,230 So he has a sample network. 25 00:02:41,240 --> 00:02:53,700 Notice that this device 170 or 30 1.0 that one is on network 1 7 2 0 or 31 0 0 1 7 2 is a Class B network 26 00:02:54,050 --> 00:03:02,300 so the network portion of the address is 170 to 31 and the host portion of the address is 0.0. 27 00:03:03,140 --> 00:03:12,560 This device is sending a directive to broadcast to 1 7 2 or 31 or 255 255 using a hacking tool such 28 00:03:12,560 --> 00:03:14,840 as Smurf as an example. 29 00:03:14,870 --> 00:03:23,370 In other words it's sending a broadcast to this subnet 1 7 2.30 1.0 its era. 30 00:03:23,390 --> 00:03:30,590 Now a router will switch configured to forward directed broadcasts will forward that directed broadcast 31 00:03:31,070 --> 00:03:43,430 to network 1 7 2 or 31 0.0 and all devices on that subnet including this device 173 1.0 that one will 32 00:03:43,430 --> 00:03:45,780 receive back to port cost. 33 00:03:45,860 --> 00:03:52,550 So it all hosts on that segment will receive the directed broadcast who will accept it. 34 00:03:52,550 --> 00:03:57,770 So in other words the network interface cards will accept the broadcast and forward it to highlight 35 00:03:57,800 --> 00:04:06,850 protocols for processing the s.p use of every device will be interrupted to process the directed broadcast. 36 00:04:06,860 --> 00:04:13,700 Now normally attackers would say and the directed broadcast from the device that they want to attack 37 00:04:14,120 --> 00:04:17,860 in other words they may be using a different IP address. 38 00:04:17,900 --> 00:04:21,430 For example one 1:53 16.00 or ten. 39 00:04:21,510 --> 00:04:28,610 But if they wanted to attack this device one 17:16 zero or one they would say and directed broadcasts 40 00:04:28,790 --> 00:04:33,280 to the subnet one 1:53 at 31 that 0.0. 41 00:04:33,290 --> 00:04:42,590 In other words they would launch lots of traffic with a source IP address of one 17:16 0 to 1 to destination 42 00:04:42,680 --> 00:04:46,110 1 7 2 30 1 2 5 5 2 4 5. 43 00:04:46,190 --> 00:04:51,760 All devices on the subnet would then reply back to the source address. 44 00:04:51,790 --> 00:04:58,340 One 17:16 0 to 1 causing a denial of service attack on that device. 45 00:04:58,370 --> 00:05:05,420 So a hacker is getting legitimate hosts on the network to cause a denial of service attack on another 46 00:05:05,420 --> 00:05:07,370 host on the network. 47 00:05:07,370 --> 00:05:14,060 Now once again directed broadcasts are not permitted by Cisco devices these days to prevent these kind 48 00:05:14,060 --> 00:05:17,240 of attacks using applications such as smurf. 49 00:05:17,240 --> 00:05:24,050 Smurf is an example of an application that allows you to launch a denial of service attacks using directed 50 00:05:24,050 --> 00:05:25,640 broadcasts. 51 00:05:25,760 --> 00:05:33,170 That's not as common today because the rod isn't switches drop directed broadcast traffic by default.