- When Cisco discusses switching
in regards to their exam objectives,
they're talking about Layer 2 Switching,
unless they say otherwise.
Layer 2 Switching is the process
of using the hardware address
of a device on a LAN to segment a network.
Since we already covered the basic idea of how that works,
we're going to dive deeper into the particulars
of Layer 2 Switching to ensure that the concept
of how it works is solid and complete.
Switches break up large collision domains into smaller ones.
And a collision domain is a network segment
with two or more devices sharing the same bandwidth.
A hub network is a typical example
of this type of technology.
But, since each port on a switch
is actually its own collision domain,
we were able to create a better Ethernet network
by simply replacing our hubs with switches.
Switches truly have changed the way
networks are designed and implemented.
If a pure switch design is implemented correctly,
it will result in a clean, cost-effective,
and resilient inter-network.
In this video, we'll survey and compare
how networks were designed before
and after switching technologies were introduced.
Unlike old bridges, which use software to create
and manage a content-addressable memory filter table,
our new fast switches use something called
application-specific integrated circuits, or ASICs,
to build and maintain their MAC filter tables.
If you're familiar with multi-port bridges,
it's still okay to think
of a Layer 2 Switch as a multi-port bridge
because their basic reason for being is the same.
To break up collision domains.
Layer 2 Switches and bridges are faster than routers
because they don't take up time
looking at the network layer header information.
Instead, they look at the frame's
hardware addresses before deciding
to either forward the frame to the intended host,
flood the frame out to all the other switchboards,
or even drop the frame.
Unlike hubs, switches create private,
dedicated collision domains
and provide independent bandwidth exclusive to each port.
There are four important advantages to Layer 2 Switching.
Hardware-based bridging with ASICs.
Wire speed.
Low latency.
And now, low cost.
A big reason Layer 2 Switching is so efficient,
is that no modification to the data packet takes place.
The device only reads the frame encapsulating the packet
which makes the switching process considerably faster
and less error-prone than routing processes.
And if you use Layer 2 Switching
for both work group connectivity and network segmentation,
which is breaking up collision domains
and Cisco calls this Microsegmentation,
you can create more network segments
than you can with traditional routed networks.
Plus, Layer 2 Switching increases bandwidth for each user
because, again, each connection or interface into the switch
is its own, self-contained collision domain.