Original subtitles

Now that we've discussed address Klosters in IP version 4 we're going to continue the discussion looking

at special addresses such as the local broadcaster trace loopback addresses and other special addresses

that you'll encounter in IP version 4.

We also look at network mosques and Sajda or close listening to the main routing and we'll see how that

affects the network and host portion of addresses in IP version 4.

So now let's look at some of the special addresses that you'll encounter in your networking Korea.

The first one is directed broad cost address a directed broad cost address is used by hosts to send

data to all devices on the specific subnet or specific network in direct broadcast addresses the entire

host portion of the address is populated with binary ones.

So as an example if we have a network of 172 docked thirty one 0.0 the directed broadcast address is

1 7 to Dr 31 to 2 5 5 2 2 5 5 notice because this is a class be it race.

The first two octets denotes network and the last two octets denotes host portion of the address.

So the host portion is filled with binary ones 255 in decimal equates to eight binary ones.

So the host portion is therefore populated with binary ones in both the third and fourth octet.

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

broadcasts but by default directed broadcasts are not routed from one physical interface to another

physical interface or from one villain to another villain.

They are hacking utilities that you can download and use to launch denial of service attacks or decrease

attacks by using directed fraud costs and thus for security reasons it's recommended that the forwarding

of directed proved costs be disabled.

This is the default on modern versions of the Cisco IOS.

So routers and switches will not forward directed broadcasts from one villain to another we'll run them

from wanting to face to another interface.

So he has a sample network.

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

so the network portion of the address is 170 to 31 and the host portion of the address is 0.0.

This device is sending a directive to broadcast to 1 7 2 or 31 or 255 255 using a hacking tool such

as Smurf as an example.

In other words it's sending a broadcast to this subnet 1 7 2.30 1.0 its era.

Now a router will switch configured to forward directed broadcasts will forward that directed broadcast

to network 1 7 2 or 31 0.0 and all devices on that subnet including this device 173 1.0 that one will

receive back to port cost.

So it all hosts on that segment will receive the directed broadcast who will accept it.

So in other words the network interface cards will accept the broadcast and forward it to highlight

protocols for processing the s.p use of every device will be interrupted to process the directed broadcast.

Now normally attackers would say and the directed broadcast from the device that they want to attack

in other words they may be using a different IP address.

For example one 1:53 16.00 or ten.

But if they wanted to attack this device one 17:16 zero or one they would say and directed broadcasts

to the subnet one 1:53 at 31 that 0.0.

In other words they would launch lots of traffic with a source IP address of one 17:16 0 to 1 to destination

1 7 2 30 1 2 5 5 2 4 5.

All devices on the subnet would then reply back to the source address.

One 17:16 0 to 1 causing a denial of service attack on that device.

So a hacker is getting legitimate hosts on the network to cause a denial of service attack on another

host on the network.

Now once again directed broadcasts are not permitted by Cisco devices these days to prevent these kind

of attacks using applications such as smurf.

Smurf is an example of an application that allows you to launch a denial of service attacks using directed

broadcasts.

That's not as common today because the rod isn't switches drop directed broadcast traffic by default.