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Now that we've discussed address Klosters in IP version 4 we're going to continue the discussion looking
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at special addresses such as the local broadcaster trace loopback addresses and other special addresses
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that you'll encounter in IP version 4.
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We also look at network mosques and Sajda or close listening to the main routing and we'll see how that
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affects the network and host portion of addresses in IP version 4.
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So now let's look at some of the special addresses that you'll encounter in your networking Korea.
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The first one is directed broad cost address a directed broad cost address is used by hosts to send
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data to all devices on the specific subnet or specific network in direct broadcast addresses the entire
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host portion of the address is populated with binary ones.
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So as an example if we have a network of 172 docked thirty one 0.0 the directed broadcast address is
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1 7 to Dr 31 to 2 5 5 2 2 5 5 notice because this is a class be it race.
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The first two octets denotes network and the last two octets denotes host portion of the address.
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So the host portion is filled with binary ones 255 in decimal equates to eight binary ones.
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So the host portion is therefore populated with binary ones in both the third and fourth octet.
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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
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broadcasts but by default directed broadcasts are not routed from one physical interface to another
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physical interface or from one villain to another villain.
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They are hacking utilities that you can download and use to launch denial of service attacks or decrease
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attacks by using directed fraud costs and thus for security reasons it's recommended that the forwarding
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of directed proved costs be disabled.
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This is the default on modern versions of the Cisco IOS.
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So routers and switches will not forward directed broadcasts from one villain to another we'll run them
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from wanting to face to another interface.
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So he has a sample network.
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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
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so the network portion of the address is 170 to 31 and the host portion of the address is 0.0.
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This device is sending a directive to broadcast to 1 7 2 or 31 or 255 255 using a hacking tool such
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as Smurf as an example.
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In other words it's sending a broadcast to this subnet 1 7 2.30 1.0 its era.
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Now a router will switch configured to forward directed broadcasts will forward that directed broadcast
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to network 1 7 2 or 31 0.0 and all devices on that subnet including this device 173 1.0 that one will
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receive back to port cost.
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So it all hosts on that segment will receive the directed broadcast who will accept it.
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So in other words the network interface cards will accept the broadcast and forward it to highlight
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protocols for processing the s.p use of every device will be interrupted to process the directed broadcast.
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Now normally attackers would say and the directed broadcast from the device that they want to attack
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in other words they may be using a different IP address.
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For example one 1:53 16.00 or ten.
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But if they wanted to attack this device one 17:16 zero or one they would say and directed broadcasts
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to the subnet one 1:53 at 31 that 0.0.
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In other words they would launch lots of traffic with a source IP address of one 17:16 0 to 1 to destination
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1 7 2 30 1 2 5 5 2 4 5.
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All devices on the subnet would then reply back to the source address.
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One 17:16 0 to 1 causing a denial of service attack on that device.
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So a hacker is getting legitimate hosts on the network to cause a denial of service attack on another
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host on the network.
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Now once again directed broadcasts are not permitted by Cisco devices these days to prevent these kind
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of attacks using applications such as smurf.
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Smurf is an example of an application that allows you to launch a denial of service attacks using directed
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broadcasts.
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That's not as common today because the rod isn't switches drop directed broadcast traffic by default.
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