We've got a quick and to the point video
for you today, and it's all about power. Imagine you need to connect a few desk
phones, wireless access points
and security cameras to your network. They will require power, of course,
but you don't necessarily want to put a big power socket
next to each device. They take up a lot of space. They can look a bit ugly
and the cabling can get messy. Fortunately, we have an alternative,
which is power over Ethernet. That is where we supply power
over a regular network cable. Any device that connects to our network
that we can power using power over
Ethernet is called a power device, or PD. The generally smaller devices
like this phone that only require a few watts of power to stop. We simply connect the network cable to the back of our phone, and we'll see
that it starts booting up automatically . No extra power needed. Cisco originally introduced
powered interfaces over 20 years ago. It was called Cisco inline power,
and it could deliver up to seven watts of power per port. The maximum port speed for
this standard was 100 Meg. This was a Cisco only technology, so if you wanted it,
you needed to have a Cisco switch. It was a pretty good idea, though. So since then, the EA has released several standards that any vendor can use. The original Pope standard was 80, 2.3 a f, which is now known as type one p o e. It uses two powered YS and provides 15.4 watts of power per port. Type one power is still used
quite commonly, and he's really good for powering small appliances like desk
phones and small wireless access points. You probably
know that we measure power in Watts. Like any power solution, there is a little
power loss as power runs over the cable. It's no different with network cables. So type one power supply is a 15.4
watts at the port, but only guarantees
12.95 watts at the power device. Just to explain this terminology a bit. Any device that supplies power is called
a PC or power sourcing equipment. Any device that consumes the power is called a PD or power device. There are some other devices that simply
need more power in order to run. These include
things like a four in one security camera, tablets, LCD screens and plenty more soap plus was developed. This supplies 30 watts of power per port. But why stop there? We now have two additional POW plus plus
standards called type three and type four. And they can deliver
61 hundred watts per port. Cisco have their own versions of these call ups and UPO Plus. Most notably, these standards power up to two pairs of wires
in the network cable. These higher powered standards are good
for teleconferencing solutions. Kiosk terminals, small switches, laptops
and small TV screens. Each of these standards is a power class power devices can change their power
class over time if needed. For example, a device may need
only type one to power up later on. It might need to turn on a screen,
so it might signal a switch that needs a change to type
two, three or four. The next question is, does it matter
what kind of cabling we use? Yeah, a bit. It obviously has to be copper cabling. You simply can't supply power over fiber. Also, it
should be no longer than 100 meters long, and ideally
it needs to be cat five or better. But here's the really big question, is Pope safe? Well, it is a much smaller amount of power
than you would have in your average wall socket. Also, it uses DC power, not AC, which makes it much safer at small power
levels. Additionally,
the Tripoli Standard says that iPSC will only supply power to a device
that requests it. So if you plug in a device that doesn't
have a need for power, it won't get fried. So it was relatively safe. It is still power, so you still should use
appropriate caution. Don't go looking your network cables
or anything like that, although to be fair, if you're the kind of person that leaks
power cables, you're probably in the wrong industry. OK, we have a few quiz questions,
but they're pretty easy in this video, I'm sure you're happy for a break. We've been talking about using switches
as power sourcing equipment. This is the nicer solution,
but there are other options. For example, this play injector. This is a separate device that combines
the network signal from the switch with power from some other power source. So if you have a switch,
it doesn't support power. This might be a suitable alternative. one common use of this power injector would be to power
an outdoor wireless access point, which are often too far away
from the switch for regular power to work. Similar to an injector,
you can also get a splitter. This is where you have something
providing power, but the device doesn't natively support
being powered through power. For example, a Raspberry Pi, it has a power source
that's separate to the networking device, so a split up will separate the power from the data, allowing you to plug
in both cables separately. The advantage to this
is that you don't need a wall socket to power all your devices,
even if they don't support Bowie. But please remember, there isn't a
bottomless pit of power available to you. Each switch has a power budget. The power budget is the maximum amount of power that it can supply with poetry,
for example, ones which I've use in past is a small twelve port switch
and has a power budget of about 100 watts. This means
I could enable power on only six ports or I could have power
plus on up to three ports. Or some combination
thereof that is less than 100 watts. So keep this in mind
when you're buying a new switch. Generally, you can get the
which is datasheet like the one shown here from the switch vendor,
which gives you this information. I think the interesting takeaway from this
is how the power budget is calculated. Let's say you have a desk phone
connected to an interface. You enable play on the interface, which can supply up to 15.4 watts. However, a simple desk phone is unlikely to draw all 15 watts. It may draw only five watts
when calculating your power budget. Work with the amount of power
that the interface can supply. What I mean is assume that the phone
will consume all 15.4 watts of power. If you had
that switch with a budget of 100 watts, you wouldn't assume that you could run
two phones at five watts each. You need to assume
that you can only have six phones at 15.4 watts each. This is because each connected
device may start drawing more power than you expect
up to the limit of that port. Also, when looking at data sheets,
they may provide two values the total power of the switch consumes
and the power budget. For example, a switch
may consume up to 830 watts of power. Remember, though, that it needs to consume
some power itself just to turn on run. So while it may consume up
to 830 watts of power, 720 watts, maybe for power, while 110 watts
may be for the switch itself. Some switches allow you to add a second power supply,
depending on the model adding a second power supply
will increase your total power budget. So our 830 watts,
which may then consume up to 1550 watts of power, still 110 watts for the switch itself, but now 14 140 watts of power, a budget that makes sense. And here are the last two quiz questions. I really hope these quizzes have been helpful to you
and you've been learning from them. We've reached the end of our section
on layer two technology and switching in the next section, we're going to look
at layer three and routing, starting with a basic review
on IP addresses and the routing table. Please join me there.
