So guys, we have already understood the concept of VLANs.
Now let us discuss that.
What other benefits VLANs can provide us.
So you can see in this diagram the host, A, E, B and F, that is host A host.
E, host B and host F are completely unaware of any communication taking place between the host C and
host D, Right.
And this property of VLANs is called segmentation.
So you can see that the host C and host D are present in Vlan ten, whereas host A and host F are present
in Vlan 12, whereas host E and host B are present in Vlan 11.
Right.
So basically we have splitted up this entire network into three different isolated Subnetworks.
So host C and D are present in Vlan ten and host A and F are present in Vlan 12.
Similarly, host B and E are present in Vlan 11.
So any kind of communication that is data exchange taking place between the machines present in one
Vlan is completely isolated from any machine which is present outside that Vlan.
So basically using the concept of VLANs, we have split it up one physical layer to switch into multiple
logical L2 switches.
So let us map this scenario to a real world problem.
You would definitely want the finance and research department of your company to work in complete isolation
with each other.
Right.
And this is what is accomplished here.
Now coming to the point that villains create an illusion that a physical Layer two switch is split up
into multiple logical switches.
So you can see in this diagram that we have one L2 switch and the host, H1 and the host H4 are present
in the same Vlan.
In other words, they are present in the same network, whereas host H2 and host S3 are present in Vlan
11.
So you can see that different colors of these lines actually represent the isolation.
Any traffic or data that is placed on red line will never be leaked to pink line, and any data that
is placed on pink line will never be leaked on red line.
So you can see in this diagram we have an L2 switch which has actually splitted up the network into
two isolated subnetworks.
These two subnetworks are Vlan ten and Vlan 11.
Right.
So no traffic ever leaks from Vlan ten to Vlan 11 in this topology.
Host machines present in one subnet that is in one Vlan.
Never ever communicate with the host machines present in another vlan.
Now this topology can be thought of equivalent to the topology on the right hand side.
Now, on the right hand side, the L2 switches that we are using are actually Vlan unaware L2 switches.
That is, they do not know the concept of VLANs.
So in order to keep the host machines which are connected to red lines, that is Vlan ten completely
isolated from the host machines which are present in Vlan 11.
That is, which are connected to pink lines.
We would need two Vlan unaware L2 switches in order to preserve isolation.
So you can see that in this example we VLANs split one physical L2 switch into two logical switches.
So here you can see that the concept of VLANs has actually helped us to simulate the behavior of multiple
logical switches onto one physical layer two switch.