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.