- So if we don't have routers
and we have switches or microsegmentations
like Cisco likes to call it
where every host is in a switch port,
we can see here that Bob is shouting or
sending out a broadcast.
This is transmitted out all ports on a switch by default.
So we can see that this is one big broadcast domain
but this is the functions of switch.
We don't break up broadcast domains by default.
We do break up collision domains.
Now in this case here we're going to create
an internetwork by placing a router between
these two lans and by creating two different
subnets or lans.
In this case here when Bob is to send a broadcast
then it's sent only to the router and then discarded.
Routers do not forward broadcasts by default.
In this case here Sally does not receive any of the data
from Bob unless he specifically
is sending data to her IP address.
Now it's important to remember for the objectives
that you have different networking devices.
Let's take a look at some of the devices
that are new to the objectives.
First, we have our wireless networks.
We have an access point which is just basically a hub
but instead of sending digital signals
we have digital signals here coming in
but coming out this way is analog signaling.
Right, so this really is truly a modem
or modulator demodulator.
In this case here, it's going to run half duplex.
Now we could run full duplex from here to here
but in this case here the AP is going to connect
our wireless hosts to the switch
and just extend this collision domain.
We also have our VOIP or our IP phones.
We have our wireless lan controllers.
Now this is somewhat new for the CCNA
but a wireless lan controller manages my wireless
access points and frames, wireless frames,
on the network.
They control the wireless traffic.
We also have our firewalls.
And this is referred to today as our next generation
firewall or next generation IPS.
Firewalls are absolutely essential for todays's networks.
So what's new on here again?
Our wireless lan controller which manages
our wireless frames and our access points
and provides the configuration and codes for access points.
Our IP phones and our firewalls.
Now we can create a large switched network.
We call this a flat network because by default
it's one large broadcast domain.
But in this example here we have our router
and then we have our layer two switching it
unless Cisco tells you differently
when you see a switch everything is referred to as
layer two switching.
Now in this example here we'd have our different connections
to our hosts and these switches then connect up to
this would be considered our access layer.
This is considered our distribution layer
and in this case here we could run a layer three switch
to provide inter VLAN routing, IVR,
which provides routing between VLANs.
So a VLAN is a breaking up of broadcast domains
in a layer two switch network.
So in this example here where I can have this one
in different broadcast domains, this one would be in
say VLAN 2.
This one would be in 3 and this one would be in 2 and 3.
And these guys could both be in 4.
There in different subnets, different broadcast domains.
And we just refer to them as being in different VLANs
or virtual lans.
For example, a host in VLAN 2 can communicate
to a host in VLAN 3.
Now we'll talk about this later
but just understand that for a host to talk from
one VLAN to another they have to go through some
sort of layer three device such as a layer three switch
or through a router.