So guys, we have just learned that L2 switches separates the collision domain.
That is, it splits the bigger collision domain into smaller ones and make the network more efficient.
Now let us see that.
How L3 Routers impact the broadcast domain and collision domain.
So in this topology, you can see that we have an L3 router here and this L3 router actually hosts three
different subnets on its three physical interfaces.
Now, because they are three different subnets, it means that they are three different broadcast domains.
The broadcast packet that is generated by the host, one will be confined to this subnet and therefore
it is a broadcast domain for the host H1.
Similarly for the host H2, this will be the broadcast domain.
And similarly for the host H3, this will be the broadcast domain.
So you can see that L3 routers separate the broadcast domain.
In fact, each subnet is a broadcast domain.
So this is pretty much simple that every interface on an L3 router is a one complete subnet and that
subnet is a one complete broadcast domain.
Now I have once again mentioned the standard definition of broadcast domain and collision domain.
So in this topology we will going to find the broadcast domain and collision domains.
So let us take a host machine B, and let us try to find the broadcast domain with respect to the host
machine B.
So if Host Machine B generates an ARP broadcast message, what are the machines which will going to
receive that are broadcast message?
That machine will going to be the machine, a machine.
E And this particular interface of this L3 router, it means that the broadcast domain of the host machine
B will going to be this region which is enclosed by this pink borderline.
Similarly, apply the same concept.
What will be the broadcast domain for the host machine?
See the broadcast domain for the host machine C.
Is demarcated by this pink border line.
Now, coming to this link between these two L3 routers.
Now, if this L3 router generates an ARP broadcast message and place that message on this physical wire,
that message will going to be received by only the L3 router on the other side.
So the broadcast domain will be confined in between these two L3 routers.
So you can see that in total there are three broadcast domains.
In fact, there are three different subnets.
Hence there are three different broadcast domains.
Now let us try to find the collision domain.
Now let us try to find the collision domain with respect to the host machine B.
Now, when the host machine B places its frame on the physical wire, then rest of the machines which
are connected to this physical wire is the host machine A and the L2 switch.
Therefore, the collision domain of host machine B is shown by this shaded region.
Similarly, the collision domain with respect to the host machine e will include this particular interface
of an L2 switch and the host machine E itself.
Right.
Similarly, the collision domain for host Machine C and D are shown by these shaded regions.
Similarly, applying the same concept, you can find that this is one collision domain.
This is another collision domain.
And.
The link between two L3 routers is also a collision domain.
So in total there are three broadcast domain and seven collision domains.
Note the point that P2P links are both broadcast domain and collision domains.