All language subtitles for Free-CCNA-Wireless-Fundamentals-Day-55-CCNA-200-301-Complete-Course_en

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In this video we’ll take a look at the fundamentals\n

The exam topics we will cover are 1.1.d, access\n

We will cover these and other wireless exam\n

but this video will be a general overview\n

Here’s what we’ll cover in this video.

I’ll introduce radio frequency, RF.

RF is a range of electromagnetic wave frequencies\n

including AM and FM radio, microwaves, radar,\nand Wi-Fi.

The last one is of most interest to us, of\n

I’ll talk about Wi-Fi standards as defined\nin IEEE 802.11.

Just like various Ethernet standards are defined\n

We’ll look at some fundamentals of wireless\n

We’re going to cover a lot of new concepts\n

When learning new concepts taking notes is\n

organized without feeling overwhelmed.

Make sure to watch until the end of the video\n

ExSim for CCNA, my recommended practice exams\nfor the CCNA.

First let me introduce wireless networks,\n

Although we will briefly look at other types\n

course we will be focusing on wireless LANs\n

The standards we use for wireless LANs are\n

Ethernet LANs are defined in IEEE 802.3.

Note that the term Wi-Fi is a trademark of\n

The Wi-Fi Alliance tests and certifies equipment\n

Devices which have been Wi-Fi certified can\n

For example, this is a photo of the back side\n

that I will be using to make these videos.

As you can see, it has been certified by the\nWi-Fi alliance.

So, although the Wi-Fi alliance certifies\n

Wi-Fi isn’t technically the correct term\n

However, Wi-Fi has become the common term\n

LANs and I will use both terms throughout\nthese videos.

Wireless networks have some issues that we\nneed to deal with.

First of all, all devices within range receive\n

When using an Ethernet switch, the switch\n

In addition, switches allow devices to function\n

and receive frames at the same time and collisions\n

However when using an ethernet hub, the hub\n

and collisions can occur when multiple devices\n

Like devices connected to an Ethernet hub,\n

wireless-enabled devices within range will\n

The signal isn’t contained within a physical\n

waves radiating out from the transmitting\ndevice.

This can lead to data privacy concerns, as\n

on the same channel at the same time.

So, because all devices within range receive\n

In wired networks we don’t usually encrypt\n

over a shared network such as the Internet.

However, for wireless networks it is very\n

LAN, or else anyone with a device in range\n

Also, to avoid collisions and facilitate half-duplex\n

access with collision avoidance, is used.

That’s similar to another term I mentioned\n

CSMA/CD is used in wired networks to detect\n

CSMA/CA is used in wireless networks to avoid\n

Basically, when using CSMA/CA a device will\n

before it transmits data itself.

Let’s look at a simple flowchart of the\nprocess.

The transmitting device assembles the frame,\n

Then it listens to check if the channel is\nfree.

If the channel is not free, it will wait for\n

If the channel is free this time, it will\ntransmit the frame.

Note that this is a simplification of the\n

in which the transmitting device sends a ‘request\n

to send’, CTS, packet from the receiver\n

But this is just extra information, not something\n

But make sure you know the term CSMA/CA and\n

Another issue that we must deal with is that\n

international and national bodies.

You aren’t allowed to transmit data on any\n

allowed to use can vary depending on the country.

Fortunately, the 802.11 standard outlines\n

LANs, and devices are designed to use those\nfrequencies.

We also must consider the wireless signal\ncoverage area.

In wired connections we do have to consider\n

interference, but with wireless connections\n

First of all, the signal range, how far the\n

And there are several factors that effect\n

Absorption, reflection, refraction, diffraction,\nand scattering.

Let’s briefly look at each of them.

Absorption happens when a wireless signal\n

into heat, weakening the original signal.

By the way, I took this screenshot from EMANIM,\n

Check out the link I put below the image to\n

So, a wireless access point sends a signal,\n

The wall absorbs some of the signal, resulting\n

Reflection happens when a signal bounces off\n

This is why Wi-Fi reception is usually poor\n

the metal and very little penetrates into\nthe elevator.

For example if there is a metal wall between\n

will not receive a good signal from the AP\n

Refraction happens when a wave is bent when\n

For example, glass and water can refract waves.

Try putting a straw into a clear glass of\nwater.

It will appear as if the straw is bent.

That’s because the light waves travel at\n

Diffraction happens when a wave encounters\n

This can result in blind spots behind the\nobstacle.

For example, this PC is blocked by some object,\n

travel around the object to some degree, but\n

sufficient signal from the access point.

Scattering happens when a material causes\n

Dust, smog, uneven surfaces, etc can cause\nscattering.

Forgive the unprofessional diagram again,\n

point strikes this uneven surface, the signal\n

All of those, absorption, reflection, refraction,\n

When planning the positioning of wireless\n

One more issue I want to mention is interference.

Other devices using the same channels can\ncause interference.

For example, a wireless LAN in your neighbor’s\n

So, I think you can see that there are various\n

a wireless network that we don’t have to\n

Now let’s talk about radio frequency, and\n

To send wireless signals, the sender applies\n

This creates electromagnetic fields which\n

Electromagnetic waves can be measured in multiple\n

Amplitude is the maximum strength of the electric\n

For example, look at these two waves.

The red one has a higher amplitude, and the\n

Although these two waves have different amplitudes,\n

Frequency measures the number of up/down cycles\n

the most common measurement of frequency is\nhertz.

Hertz is simply the number of cycles per second.

Then of course there are kilohertz, thousands\n

Megahertz, millions of cycles per second.

Gigahertz, billions of cycles per second.

And terahertz, trillions of cycles per second.

Of course there are more, but these are the\ncommon ones.

Although they both have the same amplitude\n

and the blue one has a lower frequency.

The red one goes through more cycles per second\n

Let’s say this represents one second.

What is the frequency of this wave?

So, this is 4 cycles per second, 4 hertz.

By the way, another important term is period,\n

So, if the frequency is 4 Hz, the period is\n

The visible frequency range is from about\n400 THz to 790 THz.

But the range we’re concerned with, radio\n

and it’s used for many purposes.

Actually we’re only concerned with a couple\n

Thanks to Wikipedia for this chart of the\n

The text is a bit small so it might be hard\n

I just want to point out the two ranges used\nfor wireless LANs.

IEEE 802.11 wireless LANs use a few sections\n

Wi-Fi uses two main bands, meaning frequency\nranges.

First is called the 2.4 GHz band.

The name is 2.4 GHz, but the actual range\n

This time the actual range is from 5.150 GHz\nto 5.825 GHz.

But it’s further divided into four smaller\nbands.

Note that you don’t have to memorize any\n

If you want to become a wireless network expert\n

and bands, but for the CCNA that’s not necessary.

The 2.4 GHz band typically provides further\n

However, more devices tend to use the 2.4\n

Modern devices typically support both, and\n

Note that Wi-Fi 6, which is IEEE standard\n

to include a band in the 6 GHz range.

I’m not sure if you’ll be asked about\n

Now, each band is divided up into multiple\n

and receive traffic on one or more of these\nchannels.

I say ‘or more’ because something called\n

channels together, but I don’t think you\n

For example, the 2.4 GHz band is divided into\n

Here are the channels, and note that it differs\nby country.

Thanks to wikipedia for the chart again, by\nthe way.

Note that the ‘11b only’ here for channel\n

old and slow standard not used much any more.

Now, an important aspect of these channels\nis that they overlap.

For example, channel 1 is from 2401 MHz to\n

To avoid interference between adjacent wireless\n

which channels we configure our access points\nto use.

In a small wireless LAN with only a single\n

there are no other access points that can\ncause interference.

However, in larger wireless LANs with multiple\n

This helps avoid interference between devices\n

If overlapping channels are used, it will\n

In the 2.4 GHz band, it is recommended to\n

Here is a diagram of the channels in the 2.4\nGHz band.

Notice that channels 1, 6, and 11 don’t\noverlap with each other.

So, we can have an AP using channel 1, an\n

11 and they won’t interfere with each other.

Note that outside of north america you can\n

should really remember the 1, 6, and 11 combination.

And as for the 5 GHz band, it consists of\n

to avoid interference between adjacent wireless\naccess points.

Using those three channels in the 2.4 GHz\n

pattern to provide complete coverage of an\n

The diagram on the left shows how you can\n

as other patterns for those outside of north\namerica.

Here’s a large version of the 1-6-11 honeycomb\npattern.

Note that the coverage area of each AP overlaps\n

but the frequencies don’t overlap, which\n

When you have to provide wireless coverage\n

Just like there have been various 802.3 Ethernet\n

standards too that use different frequencies\n

Starting with the original 802.11 which was\n

also known as Wi-Fi 6, which was released\n

I know it’s a lot of work, but I do recommend\n

they use, and their maximum theoretical data\nrates for the test.

Note that these maximum data rates are theoretical.

For many reasons you’re probably going to\n

Also notice that 802.11n is known as Wi-Fi\n

as Wi-Fi 6, however there is no official Wi-Fi\n1, 2, or 3.

That’s all I have to say about this.

Take some time to memorize these different\n

Of course, I recommend using the flashcards\nto help you do that.

By the way, 802.11-enabled devices might support\n

So, I recommend checking which standards are\n

Also, for some homework try looking up the\n

For example, if you have an iPhone you can\n

Here’s an example for the iPhone 10.

It supports 802.11 A, B, G, N, and AC.

Finally let’s look at another important\n

802.11 defines different kinds of service\n

There are three main types, independent service\n

All devices in a service set share the same\n

You might have heard that term before.

The SSID is a human-readable name which identifies\n

And it does not have to be unique, although\n

that’s what you’ll be looking at when\n

Here are the SSIDs my phone can detect as\nI sit here at my desk.

Now, I said SSIDs are human-readable, meaning\n

‘Jeremy’s Wi-Fi’ or something like that.

In this case, these names aren’t exactly\n

However, I could easily change the SSID of\n

Anyway, let’s look at the different types\nof service sets.

First, an IBSS, independent basic service\n

more wireless devices connect directly without\n

These are also called ad hoc networks.

They be used, for example, for file transfer\n

However they are not scalable beyond a few\n

purposes such as quick file transfers like\nairdrop.

Next, a BSS, basic service set, is a kind\n

connect to each other via an AP, access point,\n

Remember I said there are three kinds of service\nsets?

First is independent, which I just showed\n

BSS is a kind of infrastructure service set.

The AP serves as network infrastructure connecting\n

A BSSID, basic service set ID, is used to\n

Other APs can use the same SSID, which is\n

The BSSID is the MAC address of the AP’s\n

To be part of the BSS, wireless devices request\n

Wireless devices that have associated with\n

Another important term is BSA, basic service\narea.

This is the area around the AP where it’s\nsignal is usable.

What’s different between a BSS and a BSA?

Well, a BSS is a group of devices which are\n

BSA just refers to the physical area around\n

So, BSS is a group of devices, and BSA is\na physical area.

And note that clients must communicate via\n

The traffic must flow through the AP before\n

client is in range of the sender’s signal.

To create larger wireless LANs beyond the\n

This is the second kind of infrastructure\nservice set.

Note how there are two BSSs, BSS1 and BSS2,\n

APs with their own BSSs are connected by a\nwired network.

Notice how the APs for BSS1 and BSS2 are connected\nby a switch.

Each BSS uses the same SSID, Jeremy’s Wi-Fi\nin this case.

However each BSS has a unique BSSID, notice\n

Also, each BSS uses a different channel to\navoid interference.

Notice that BSS1 is using 2.4 GHz channel\n

Clients can pass between APs without having\n

This is called roaming, when you move between\n

Note that there should be some overlap in\n

the connectivity can be lost when moving between\nAPs.

The final kind of service set we’ll look\n

An MBSS can be used in situations where it’s\n

One to provide a BSS to wireless clients so\n

to form the mesh network between the APs,\n

For example if this PC wants to send traffic\n

AP, which then bridges the traffic from AP\n

At least one switch is connected to the wired\n

This is the RAP in this network.

The other APs are called MAPs, Mesh Access\nPoints.

A protocol is used to determine the past path\n

similar to how dynamic routing protocols are\n

Now, most wireless networks aren’t standalone\nnetworks.

Rather, they are a way for wireless clients\n

and the AP serves to translate between the\ntwo mediums.

In 802.11, the upstream wired network is called\n

Each wireless BSS or ESS is mapped to a VLAN\n

The SSID Jeremy’s Wi-Fi is translated to\n

The wired hosts in VLAN 10 will be able to\n

And it’s possible for an AP to provide multiple\n

This is the same as how a switch can divide\n

Each wireless LAN is mapped to a separate\n

There are two wireless LANs with their own\n

Although as I said before, SSIDs don’t have\n

Jeremy’s Wi-Fi is mapped to VLAN 10, and\n

AP is connected to the switch via a trunk\n

Also, notice that each wireless LAN uses a\n

last digit of the BSSID by one.

So, the BSSID of Jeremy’s Wi-Fi ends with\n

The final thing we’ll cover is a few more\n

First, an AP in repeater mode can be used\n

The repeater will simply retransmit any signal\n

A repeater with a single radio must operate\n

drastically reduce the overall throughput\n

repeating the AP’s signals back to it using\n

This cuts the effective throughput of the\nchannel by 50%.

A repeater with two radios fixes this weakness,\n

then retransmit on another channel.

So, that’s how a wireless repeater works.

Next, an AP operating as a workgroup bridge\n

and can be used to connect wired devices to\n

In the example below, PC1 does not have wireless\n

to a wired connection to SW1.

However, PC1 has a wired connection to the\n

Now, there are two kinds of WGBs.

Universal WGB, uWGB, is an 802.11 standard\n

However what Cisco simply calls WGB is their\n

wired clients to be bridged to the wireless\nnetwork.

To summarize, this is a solution which allows\n

to connect to the wireless network via an\n

The final mode I’m going to introduce is\noutdoor bridge.

An outdoor bridge can be used to connect networks\n

The APs will use specialized antennas that\n

which allows the wireless connection to be\n

The connection can be point-to-point as in\n

Or it can be point-to-multipoint, in which\n

site, forming a hub-and-spoke topology.

Okay, since we covered so many different topics\n

Now, although this summarizes the topics in\n

of each topic that we covered.

If you didn’t take notes I recommend going\n

and also using the flashcards to memorize\nsome of the details.

Okay, in this video we covered the basics\n

LANs, including radio frequency, wi-fi standards,\n

There is still a lot more to cover about wireless\n

wireless network security, and wireless network\nconfiguration.

Those topics will be in the next few videos.

As always, watch until the end of the quiz\n

ExSim for CCNA, the best practice exams for\nthe CCNA.

Okay, now let’s go to quiz question 1.

When using the 2.4 GHz band, which channels\n

Pause the video now to select the best answer.

Okay, the answer is B, 1, 6, and 11.

As this diagram shows, channels 1, 6, and\n

each other interference can be avoided.

Okay, let’s go to question 2.

If an enterprise’s network is mostly wired,\n

Pause the video now to select the best answer.

Okay, the answer is to connect wireless devices\n

In 802.11, the wired network is called the\n

role is to connect wireless devices to the\nwired network.

Which of the following bands are commonly\nused by wireless LANs?

Pause the video now to select the best answers.

Okay, the answers are A, 2.4 GHz, and D, 5\nGHz.

These bands are divided into channels which\n

Which of the following statements about an\n

Pause the video now to select the best answers.

Okay, the answers are B, each BSS uses a unique\n

connectivity when moving between APs.

A is not correct because each BSS in an ESS\n

because adjacent APs should use nonoverlapping\n

Which of the following statements is not true\n

Pause the video now to select the best answer.

Okay, the answer is B, each BSS shares the\nsame BSSID.

Although it is possible for each BSS to share\n

With that said, however, it is best practice\n

Okay, that’s all for the quiz.

Now let’s try a bonus practice question\n