- [Man] Poodle, what is this? - [Poodle] It's a bridge for
all the cars to drive over. - [Man] It's a bridge
for cars to drive over? - [Poodle] Mm hmm. - [Man] Isn't it actually Ethernet bridge? - [Poodle] Yes. - [Man] Ethernet bridge, well done. What is this? - [Poodle] A hub. - [Man] A hub. What is this then, Poodle? - [Poodle] A switch. - [Man] No, this is a hub. - [Poodle] Oh, I'm sorry. - [Man] It looks like
a switch, doesn't it? - [Poodle] These two hubs are for a pub. - [Man] (man laughing)
Are they hubs for a pub? Oh I like that, what is this? - [Poodle] A router. - [Man] A router. What is this one? This is a funny one. - [Poodle] A repeater. - [Man] A repeater, it repeats signals. - [Poodle] It repeats stories. - [Man] It repeats stories? What is this one, you
know what this one is. - [Poodle] A switch, it will
turn on the light in the roof. - [Man] It's a switch that
turns on the light in the roof. Well done, and what about this one? - [Poodle] This one also is
a switch, a better switch. - [Man] It's a better switch. Here we have a whole bunch
of networking devices and in this video, we're going to learn about network devices. Oh, you've got a book, Kali Linux Hacking. You love to hack. - [Poodle] Mm hmm. - Well done, Poodle. The thing to remember
is, basic definition, routing switching, dumb device. So no intelligence here. Intelligence based on MAC addresses. Intelligence based on IP addresses. (upbeat synth music) I'll go through this in more detail later. Let's just look briefly at
some of the devices that we had in the past and then some modern devices. The original Ethernet was
10BASE5 using this really big yellow cable, so this cable
was restricted in distance. The signal would attenuate
from one end of the cable to the other and what they
developed were repeaters. This is an example of
a very early repeater. This would repeat the signal
from one port to another. We could use 10BASE5 here or 10BASE2. So this amplified the signal, basically. Didn't understand the actual
signal, but it just amplified the signal from one port to another. Now you'll notice it doesn't
have many ports on it. We've only got two ports. So it was simply repeating
from one port to another. So example of a repeater. They then developed what was
called a multiport repeater. This is a Cisco FastHub 400 series. So we've got RJ45 connectors on the front. We've got power on the
back, but the idea is a hub is essentially a multiport repeater. We've got multiple ports and we are simply repeating the signal. We would connect RJ45
unshielded twisted pair as an example, to these
ports and what a hub does is once again, it simply
repeats the signal without understanding what's going on. So it doesn't understand
the frames that it receives or the information that it receives. It simply amplifies it, so a
repeater here would amplify the signal, amplify it
from one port to another. Here, we've got a multiport repeater. It's repeating the signal from one port to multiple other ports. So if traffic was received
on port one on this hub, it would simply amplify the signal out of all of those ports. So it repeats the signal
out of every other port without understanding any of the details. Here is an example of a NETGEAR hub. On the front, we have 24 RJ45 ports and on the back, we've got 10BASE2, as well as 10BASE5. So again, this would allow me to connect different cable types on the back. We could connect 10BASE5 as an example and then on the front, we could have UTP RJ45 cabling as we know today. This has no intelligence. There is no intelligence in the hub. There's no intelligence in the repeater. Remember this is just repeating the signal from one port to another. This is a multiport repeater. If something is received on this port, it just amplifies it out
of all the other ports, or repeats it out of all the other ports. Otherwise we get attenuation of signals and the signals degrade
over a period of time, which restricts the length of a cable. This allows me to increase
the length of the cable. Now the problem in those
days is the more devices that you have on the
network, the more collisions that you're going to have,
which causes problems and slows the network down. I'll talk more about that later, but the idea is that this is
a hub, this is a repeater. We don't worry too much about these days. A lot of people say, David
don't even show me hubs because they're pointless, but they forget that wireless, this is an example of a wireless access point, very modern wireless access point supports Wi-Fi 6, the latest version of Wi-Fi
at the time of this recording, a WiFi network or a wireless
network is essentially a hub in the air, we are sharing the air. So whatever I'm saying can be heard by you if you're within range,
both of us can't speak at the same time because
it's a shared medium. We are sharing the air. Now Wi-Fi 6 does try and
implement some very clever stuff to allow multiple devices
to talk at the same time. So it kind of approaches a switch, but it's still acting as a hub. So what is a switch? Here's an example of a switch,
this is an older switch, 3750, very popular for
doing labs, cisco labs. Notice, lots of ports on the switch. We've got 48 ports on the switch. The number of ports on your switch varies. You can have very small switches. You could have larger switches. Here as an example, is a five
port switch, TP-Link switch. Very small switch, here's
another four port switch from TP-Link, so you don't
necessarily have lots of ports, but in an enterprise
environment, you typically will. You'll have a lot of ports on a switch. These are smaller switches. The point is, is that the form factor or the way that these devices look varies, but the big difference between a switch and a hub, is a switch has intelligence. A switch actually reads what are called the frames received on Ethernet. When you send data onto
Ethernet, we are sending what's called a frame, so this device uses what's called a MAC address table. It's the same as these
devices at the top here. They basically receive frames
and they have the intelligence to only forward the frames
out of the correct ports. So if there was a device
with a certain MAC address on this port, and traffic
was received on this port, going to that MAC address,
it would only be sent out of that port rather than out of all ports. A hub or multiport repeater is
dumb when traffic is received on one port, it just simply amplifies it, or floods it is the
term, out of all ports. So everyone receives that frame. Here, a switch has a MAC address table. It has some intelligence and it learns where MAC addresses are in the network and then it will only forward the traffic out of the relevant ports
based on the destination MAC address and a frame. So if traffic comes in this
port, it's going to you, based on your MAC address. It's learned that you're
connected to this port. When traffic arrives on this port, going to your MAC address,
it's only gonna be sent out of this port, whereas,
if it arrived on a hub, it would send it out of all ports. So a big difference
between a switch and a hub is a switch has intelligence. It works at what's called layer two. We'll talk about that later in a moment. So it has some intelligence
and it'll only forward the frames out of the correct ports. Now, some people would say, "But hold on a minute,
David, what is a bridge?" A bridge you can think of
as an intermediate device between a switch and a hub. So we had repeaters
first, then we got hubs and then we had bridges, which basically did things in software. They learned where the MAC addresses were of devices in the network,
and then someone rebranded their devices as switches
because they could learn MAC addresses in hardware. So they use something called an application specific
integrated circuit or ASIC. So the lines are a little bit
blurred, but for the CCNA, you don't have to worry about that. The switch learns where devices are. It learns where their MAC addresses are, and they will only forward the traffic out of the relevant ports. A bridge was an intermediate device between a switch and a hub. So historically, we had
repeaters, then we had hubs, then we had bridges, software
switches, if you like, and then we have switches today. Now notice the number
of ports on the switch. There are many, many ports on the switch. So that's one of the features of switches. They allow us to connect many devices in our local area network. They're essentially
used for sending traffic within a local area network or LAN. We're not going to try and
send it from one network to another. These operate on MAC addresses
using what's called layer two in the OSI model or TCP/IP model. Hubs are layer one devices,
they are basically dumb devices. They don't understand what they receive. These are called layer two
devices because they use Ethernet frames and then we have routers, which use IP addresses to route
from one network to another. They are called layer three devices. We'll talk about those
terms in a separate video, layer one, layer two,
layer three, layer four, and layer five to seven, you
need to know those layers. You need to know the
TCP/IP and OSI models. So don't worry too much
about that for the moment. Just get an understanding,
dumb device repeats, everything that it receives on one port out of all other ports. More intelligent device
uses MAC addresses, learns where devices are,
and then we have routers. Now your home device might look
something like this TP-Link. This is a little TP-Link router. It allows us to route from
one network to another. Typically, little routers
like this allow us to go from our Ethernet
LAN, local area network, onto the internet, so
to what's called a WAN, wide area network. So Ethernet ports, this is
how we connect our devices to the router, wireless, and then we've got a
connection to the internet. Here's a Cisco router. What you'll notice is the router is as big as the switch, but it has
far fewer ports in it. We've only got a few Ethernet ports, and then we've got other types of ports. These are what are called serial ports. Now, fortunately in the new CCNA, you don't have to learn about
these serial interfaces. They were very slow, older interfaces. The most common WAN technology
and LAN technology today is Ethernet, so Ethernet
is what you need to know. So that's why I'm spending so
much time discussing Ethernet. These older interfaces,
aren't that important today, but think of your home router. How do you connect to the internet? Maybe you've got an ADSL connection. So your service provider
mine here in the UK is British Telecom. They've given me an ADSL connection. Now some of you may be fortunate enough to have fiber to your home. So in actual fact, your
WAN connection is Ethernet in that case, but in the old days, it might've been something
like this serial interface, but notice this router, here. This is an interesting
router, 1800 Series router. This is an older router that would be used in a small medium business
or in a remote branch office of a large corporate. This device does a lot of things. It has old telephone connections here where you could put old analog phones in. So these ports here, these
FXS ports would allow you to connect an old analog
phone to the router and then this would allow
you to make telephone calls to your service provider like AT&T or British Telecom, et cetera. It's also got a WAN interface. So one of these interfaces could go here. It also allows us to
connect to the internet. It's also got like a switch part to it. So the idea here is this is
kind of like a hybrid device. Routers today mix a lot
of switching with them. Like I said, nothing is
as simple as it seems. In its purest form, a router will route from one network to another. So as an example, we are
routing from Ethernet to serial, or we are routing from
physical Ethernet to wireless, or we are routing from one
connection type to another. So as an example, this router
could support Voice over IP. We could have IP phones
talking to analog phones, but this is where it gets a
little bit less clear-cut. This is what you need to remember. A router has routing functionality. In its most basic form, a router routes from one IP network to another. So here we're talking about IP addresses such as IP version four, or
IP version six addresses. We are routing from
one network to another, as in one IP network to another. In a lot of cases, we would be routing from one physical media to
a different physical media. This is typically used for
connections to the internet or to wide area networks. So we're connecting from
a local area network to a wide area network. Switches are typically used
in the local area network, so local within the
building, as an example, local at your home. You're not gonna use this
to route to the internet or route to other sites, a
router does that function. So it routes from one network to another. Layer two switch, as this is
called, uses MAC addresses, but switches today have
routing functionality. So a switch like this is
called a layer three switch because it has routing
capabilities built into it and then it'll route from one VLAN or virtual local area network to another virtual local area network. Basically, from one
subnet to another subnet we'll talk about that later. Thing to remember is basic definition: routing, switching, dumb device. So no intelligence here. Intelligence based on MAC addresses. Intelligence based on IP addresses. ♪ 'Cause we both deserve it all ♪ (uplifting synth music)
