Intro to IT: Networking

0:00Hello.

0:01My name is Keith Barker.

0:02And on behalf of CBT Nuggets, welcome

0:04to both this video and this short set

0:06of videos on the fundamentals of networking.

0:09Now it's interesting that there's never

0:11been a baby born where the doctor said,

0:13oh my goodness, this baby is going

0:15to be a network engineer or a network technician or a network

0:19architect.

0:20They're just babies.

0:21And most of the skills that we have

0:23in the world of Information Technology, IT, and networking

0:26come from experience and practice and learning.

0:29And so I find it fascinating because I've

0:33had the opportunity to deal with networking and networks

0:36over the last 30 plus years, I find an issue when

0:38somebody's using a computer--

0:40they're doing gaming or something else--

0:41and the computer stops, and they're like full stop.

0:44What do I do?

0:46Well, I just verify the IP address,

0:48verify the default gateway.

0:49Try this.

0:49Try that.

0:50But those actions that or those thoughts

0:52that I have as I'm looking at troubleshooting a computer

0:55network, those come from some basic knowledge of how

0:58that network operates.

0:59So here's what I'd like to do.

1:01One of the biggest benefits I think to a person who's

1:04considering getting into the world of networking

1:06or learning more about what's going on behind the scenes

1:09is to spend a few minutes with me in this short course

1:13as we take a look at the basics and the fundamentals of what

1:16goes into networking.

1:18And then when we're done--

1:19these videos are like--

1:20there's like a dozen of them.

1:21That's it.

1:22And they're all less than 10 minutes.

1:23So just do one a day.

1:25Commit to that.

1:26And then when we're done with these dozen or so videos,

1:28then you can take a look and say, OK, yeah, I get it.

1:31I like it.

1:31I want to pursue it even further.

1:33And at the tail end of this little course,

1:35I'll give you some next steps and recommendations

1:37on where you might go next if you want

1:39to pursue this even further.

1:41So I'm keeping this intro really, really short,

1:43so we get right to the core of the matter.

1:45And we're going to start in the next video

1:46with some benefits of networking.

1:48I mean, why have them in the first place?

1:50And then we'll take a look at some of the building blocks

1:52that make it all possible.

1:53And the knowledge that we learn together

1:56in this little course doesn't apply

1:58to some future job or a future career

2:00but because networks are all around us,

2:03everything we learn about how that network operates

2:06and the basic fundamentals of it is

2:08going to help us become better at configuring

2:10and troubleshooting any network that we might come across.

2:14So I look forward to joining you in the rest of the videos,

2:17including the very next one.

2:18So meanwhile, I hope this has been informative for you.

2:21And I'd like to thank you for viewing.

0:00Have you ever had the experience where

0:01you've watched something, maybe a TV show or a play or a movie,

0:05and then you watch it again and you pick up stuff

0:07that you didn't the first time?

0:09And part of that's because there's so much new information

0:11coming in the first time that maybe it just wasn't

0:13possible to pick it all up.

0:15Well, if you and I want to jump into the world of networking,

0:18which is an amazing field by the way,

0:21sometimes the very first time we see it or talk about it

0:24and we work with others who are in the field

0:26there's terms and acronyms and diagrams

0:29that are being used that we may not

0:31be as familiar with as somebody else who's been in the field.

0:34So in this Nugget here's what I'd like to do,

0:36I'd like to walk you through some of the common devices

0:39that we'd see on a network, take a look at some

0:41of the benefits of why we do networking to kinda ease

0:44into the process of the big picture of why we have networks

0:48and how they function.

0:50So let's go ahead and use this topology,

0:52which is a fancy word for saying like a diagram or a picture

0:56of how the network is connected.

0:57And some of the benefits of having a network

1:00is that if we have a couple of users,

1:01let's imagine we have Bob at this computer right

1:04here computer two and we have a user name Lois

1:08and she's sitting here at computer one,

1:10if those two users need to share something, maybe it's a file

1:14or they need to work with a common like a list of customers

1:18that's kept in the database, instead

1:20of keeping that information locally

1:21on their individual computers that information could

1:24be stored on a server and then Lois

1:26could access that data on the server and Bob could as well.

1:29And that's a huge benefit of having networking

1:32to be able to share resources and access servers that

1:36are providing content without having

1:37to have all that information on each of the local computers.

1:40And some of the common things that we're

1:42going to have on networks include network devices.

1:46And network devices could include

1:47computers like computer one and computer two and computer

1:51three.

1:52It can include servers that are connected to the network,

1:55it could include printers and it could include mobile devices

1:58like iOS and Android devices.

2:01And all these networked devices have something in common,

2:03they have a network interface card and the acronym for that

2:06is a NIC or a Nick.

2:08Sometimes that's referred to also as a network adapter

2:11or network card and most network cards today

2:14are built into the device, to the computer.

2:17In the old days, we had to actually get a separate circuit

2:20board installed in a computer but most of our computers

2:23today, whether they're desktops or laptops or mobile devices,

2:27come with some type of a network interface card already built

2:30into them from the factory.

2:31And regarding network interface cards

2:33they could be either a wired network interface

2:35card where we use a physical cable that

2:37connects to that network interface card

2:39to give it connectivity to the rest of the network,

2:42or it could be wireless.

2:43So in the case of a wired connection

2:45it would look something like this,

2:46there would be a little connection

2:48here on the computer on the network interface card,

2:50they would run a cable that leads to this device that's

2:52referred to as a switch.

2:54So that's the example of a wired connection.

2:57On mobile devices and devices that

2:59have built in wireless network interface cards the way

3:01they connect to the network is they

3:03use wireless signals, radio frequency,

3:05to connect from themselves or to a device known as an access

3:09point, an AP for short.

3:12And then that access point it has physical connectivity

3:16to the network and that's how a wireless device using Wi-Fi

3:20gets its access to the network.

3:22And so if we have a user here, like Bob, and let

3:24me actually use a different color.

3:26I'm going to use black there.

3:27So if we have Bob here who's trying

3:28to access the internet his traffic, the information

3:31that he's requesting, is going to leave his network interface

3:34card, go up through the cable that

3:36goes up to what's referred to as a switch.

3:39Now a switch is just a network device

3:41that is purpose built to move data across the network.

3:45We'll take another Nugget and we'll

3:46take a look at the details of how a switch operates

3:48but for now just realized that the switch is a network

3:51device that's often used in networks to forward data

3:54towards its destination.

3:56So the traffic from Bob would go up to the switch,

3:58the switch would forward it over here to the router,

4:01the router would forward over here to the firewall,

4:03I'm just following the direction from Bob's computer

4:06out to the internet to the server.

4:07And then the firewall would forward it to this router.

4:10This router and forward it to another set of routers

4:12until finally that data arrives at the server.

4:15And once it arrives at the server,

4:16the return traffic then could go back all the way

4:19through the network until that reply traffic gets back to Bob.

4:23And each of these devices in the path, routers and firewalls

4:25and switches, they all have their unique responsibilities

4:29as far as how do they move that data towards the server

4:32or back to Bob respectively.

4:33So in this Nugget I just wanted to chat with you

4:35and introduce you to a few details about the computer

4:38networks, including that the devices that

4:41connect to the network are going to do so using a network

4:43interface card, sometimes called a network adapter or a NIC

4:47and those cards could be either using a physical cable that

4:50connects over to a switch or they

4:52could be using a wireless technology that connects over

4:55to an access point, which is connected to a switch.

4:57Then furthermore we're going to have switches, routers,

5:00and firewalls.

5:01I just wanted to point out what those

5:03look like from a graphical representation,

5:05from a topology page.

5:06And in the next video, we'll take a look

5:08at what some of the physical devices

5:10actually look like that are being

5:11represented by this topology.

5:13So I'll see you in that next Nugget.

5:15Meanwhile, I hope this has been informative for you

5:18and I'd like to thank you for viewing.

0:00I know it's very likely that we've all seen a computer

0:03before or a mobile device.

0:04But what we may not have seen or least recognized

0:07is some of the other network devices

0:08that are commonly used in computer networks,

0:10so check this out.

0:11In this Nugget, we're going to take look

0:13at the topology diagram and pictures

0:15of things like switches and routers and firewalls.

0:18And then, I'll show you side-by-side

0:20what some of those physical devices actually look like.

0:23So using this topology diagram once again,

0:26let's start off with a computer, and let's start off

0:28with this one right here.

0:30And this is computer 2 that is connected with a network

0:33interface card into a switch.

0:36So let's bring in exhibit number one.

0:38So we're going to start here with a computer.

0:40So here's a laptop computer.

0:42It's kind of an older one.

0:43I'm keeping it around for sentimental reasons.

0:45Anyway, this computer has two network interface cards.

0:48It has one for a wired connection right here using

0:50this connector.

0:51That's an RJ45 connector or an ethernet cable connector

0:55goes in there.

0:56An RJ45 is just--

0:58the RJ stands for registered jack and number 45.

1:02So an RJ45 is a typical type of connector

1:04we'd have on a network interface card.

1:06It also has built into it a wireless network interface

1:09card if we want to connect via Wi-Fi to an access

1:12point on the network.

1:12So from this computer, we would connect to a switch.

1:16So I have some cables here.

1:17And these are what they refer to as unshielded twisted pair.

1:21So in these cables, there's actually

1:23eight sets of contacts or groupings

1:26of wires that are all terminated to each of the pins.

1:30So if we take-- and these are all the same by the way except

1:32for the color.

1:33So if I take one of these-- let's take blue.

1:37So if we take blue and we connect

1:40from the network interface card on this laptop,

1:43and we just click that into place.

1:46Then, we take the other end of that cable,

1:48and we plug it into our switch.

1:50So here's our switch right here.

1:52And we just take an unused port on the switch, and plug it in.

1:56Bada bing bada boom.

1:57We now have our first leg of connectivity

1:59from the computer via a network interface

2:02card to the physical switch.

2:04Now for clients that are not using a wired network interface

2:07card like this computer right here,

2:10they're going to connect over a radio frequency via wireless

2:13through an access point.

2:14So if we want to use an access point,

2:16we need to make sure our access point is also

2:18connected to the network.

2:19So let's go ahead and walk through that next.

2:22So to do the access point, we need to have an access point.

2:24So I happen to-- ta-da--

2:26I happen to have one.

2:27This is an access point from Cisco Systems.

2:29There's a lot of different flavors and models and vendors

2:32and so forth.

2:33But basically, it's a device that

2:36sends and receives radio frequencies

2:37and also connects to a switch.

2:38So if we open it up, it has a connection

2:41for a ethernet connection to go to the switch.

2:44So we'll go ahead and take--

2:45and, again, the colors are just for convenience sake

2:49for these cables.

2:51So I'll take this cable, and I will plug it in here.

2:56So that's our Access Point, or AP for short.

2:58And we'll plug the other end of this cable

3:00into the switch just like this.

3:04And there we have it.

3:05Now an access point, because it's sending and receiving

3:07wireless signals for the clients,

3:10it needs to have some source of power.

3:11And so power can be delivered a couple of ways to this device.

3:14We can have a transformer and plug it

3:16in with an adapter right here.

3:18That's one way of giving it power.

3:19Or if our switch supports it, we can also

3:22deliver power to this access point

3:24over the existing ethernet cable that

3:27is currently using to connect.

3:28So this would-- and close that up.

3:31I'm going to do this right.

3:32So I would want to put this connection down here.

3:36It goes through the bottom, so I can actually close this.

3:41And this can be mounted on the ceiling.

3:43As far as the cable links, we'd have

3:45cables that run along the ceiling

3:47or in the floor somewhere between usually

3:49some kind of a wiring closet on that floor of the building

3:52and the location, whether it's an outlet in the office

3:55for a computer or going to an access point that's

3:58mounted off of the ceiling if that's

4:00where we're going to place it.

4:01So we're two down.

4:03We have our computer connected and our access point connected

4:05both connected to a switch.

4:08Next, if we had a need for more switch ports that

4:11were on one physical switch, we could connect switches together

4:14by running a cable between the two switches.

4:17So let's take a look at that next.

4:19So to put the two switches together,

4:21we'd use the appropriate cable.

4:22It is a little cable that goes between two switches.

4:25And I plug it into one switch and then the other switch.

4:28And now we have them logically connected together.

4:30Now there would be some configuration

4:32to do on each of those respective ports

4:34to make that all work correctly.

4:35But that's the basis of connecting it.

4:37We also have the option, depending on the switch,

4:40to connect via something other than copper cabling.

4:42We could also use fiber.

4:44So depending on your switch and what modules it has,

4:47we could also connect them together using fiber.

4:49And that's often done if we have long, long distances to go

4:52and extremely tall buildings, for example.

4:54We can use fiber to interconnect our switches together

4:57from floor all the way down to the data center, which

4:59may be in the lower floors or in the basement of that building.

5:03Next, let's take a look at connecting a switch over

5:05to a router and what the connection there

5:07and the router looks like.

5:09So this bottom device here is a router.

5:12Now physically, it's a rectangular box.

5:16Physically, it kind of looks like it

5:17might-- it could be a switch.

5:19So we'll take a closer look at the functionality,

5:21which is the important part, between a switch and a router.

5:23We'll save that for a couple separate Nuggets.

5:25But for the connectivity between a switch and the router,

5:28we get yet, again, a cable.

5:30And we plug into one of the ports on the switch,

5:33and we'd plug in to one of the ports on the router.

5:36And that's how we get our physical connectivity

5:38between the switch and the router.

5:39And once again, the router would need a little bit

5:41of configuration based on the specific vendor

5:43that we're working with to get it operating and correctly

5:47working in our network.

5:48Next, let's take a look again at connectivity

5:50between our router and a firewall

5:53to see what that physical device could look like.

5:56And what we do to connect from the router,

6:00we can use one of the ports on the router.

6:01And we go ahead and connect to a firewall.

6:05Now, this is an example of a Palo Alto firewall.

6:08This is like their baby bear version.

6:10And all these devices--

6:11the routers and firewalls-- they have

6:13various sizes based on the vendors and what's needed.

6:16So this is a little entry level firewall

6:19from Palo Alto Networks, which by the way,

6:22Palo Alto makes a fantastic firewall.

6:24So what we do is connect from the router to the firewall.

6:28And that's how we get our connectivity there.

6:30So the play by play is the PC is physically connected to switch.

6:34The switch is physically connected to the router.

6:36The router is physically connected to the firewall.

6:38And the firewall can then connect out

6:40to the next router or next device

6:42on the path to the other networks

6:44that we need to go ahead and reach.

6:45Now one other thing before we go here is that sometimes

6:48in a small office/home office-- and there's an acronym for that

6:51like SOHO, small office/home office--

6:54we have devices that have integrated everything.

6:57So we could have, for example, switch

7:00ports, a switch built in to this device.

7:04We could have the routing function

7:05built into this device.

7:07We could have the access point built in to this device.

7:12And that's why most home routers have those three

7:15components built in.

7:16Switching ports, routing capability,

7:19and wireless access point capability all

7:22built in to one easy to configure device that's

7:26affordable for most homeowners.

7:27So we'll take a closer look at that one

7:29as well too as we proceed through this course together.

7:32So thanks for joining me in this tour of the physical devices

7:35and how they map to the devices in our topology.

7:37And I'll see you, my friend, in the very next Nugget

7:40as we take a look at more details on networks.

7:42Meanwhile, I hope this has been informative for you.

7:45And I'd like to thank you for viewing.

0:00I thought to myself in preparation for our time

0:02together and enjoying this Nugget, what can

0:04we do to get the most bang for the buck?

0:06And so here's our plan.

0:07What we're going to do is let's take a look at the big picture

0:09of how a network operates.

0:11We'll remove some of the mystery of how it works.

0:14And as we do so, we'll also touch on some vocabulary terms

0:17so that when you and I hear those terms,

0:19we'll say, ah, I get it.

0:20I know what that means.

0:22Let's begin.

0:23And let's use this topology.

0:24Let's imagine we have a user Bob right here at computer 2

0:28and that this server right here on this local network

0:31is a web server.

0:34So let's imagine that Bob, using a browser,

0:37wants to open up that browser and connect to this server

0:40and get a web page.

0:41That's our objective.

0:43Now from an oversimplified way of looking at it,

0:45we just tell Bob to put in the name of the website

0:47he wants to reach, press Enter, and, poof,

0:50it just happens like magic.

0:51But for you and I, it would make sense

0:54to peel back the onion a little bit

0:56and take a look at some of the other details that are

0:58happening behind the scenes.

1:00And as we pull back these layers,

1:01let's go ahead and draw a table.

1:03And if you want to do this along with me,

1:05that would be fantastic.

1:06I'm going to start with a fairly, big box.

1:09And then I'm going to draw four lines inside of that--

1:111, 2, 3, and 4.

1:17And then just for grins, I'm going

1:18to go ahead and put a little line here

1:21and also a little line right here.

1:23And we'll start from the top down

1:24as we identify behind the scenes a lot of the work and details

1:28that are going on.

1:29So Bob's computer is--

1:30when he's going onto a website, his browser

1:33is requesting a service.

1:34Now there's lots of services that we can get on a network.

1:38We can have web services.

1:39We could have file services.

1:43We could have streaming services for music and video

1:46and a lot of other types of things as well.

1:48So Bob's computer is going to be requesting

1:50some type of service.

1:51In this example with a web page that Bob's trying to get to,

1:54he would be looking for some type of a web service.

1:56Also, sometimes that's called an application.

1:59So the application may be web services or an application,

2:02maybe file services, or an application may be streaming.

2:06And that's the application or the service

2:08that Bob is trying to use.

2:09So whenever we hear the concept of a network service,

2:12we can also kind of think of a network application

2:14or what the network is being used for, what it's delivering.

2:17Also in that light, Bob, in this case,

2:18would be a client who is making the request.

2:22And the server would be considered

2:23a server who's delivering results back to the client.

2:26So Bob is asking a web server for a web page.

2:29In the request, it needs to be clear about what

2:31he's asking for.

2:32So before he sends that request over,

2:34somewhere in that request, we have

2:35to identify the application that Bob is asking for.

2:38And so we'll put that up here.

2:40And also over here on the left, I'll just write app.

2:43That's the app that Bob is looking for.

2:45Now, in addition to that, when we make requests

2:47over the network, there are a lot of other details

2:50that need to go into the request for that web service,

2:53including something called a transport layer protocol.

2:57And that's what we're going to call this layer right here,

2:59the transport layer.

3:00And our computers are going to choose the correct transport

3:03layer protocol.

3:04Now protocol is just a fancy word for a set of rules.

3:08And the two major protocols that are in use today

3:11on the internet are TCP.

3:14These are transport layer protocols.

3:16And TCP stands for Transmission Control Protocol, or UDP, which

3:20is User Datagram Protocol.

3:22There are a few others, but those are the two main ones

3:24that are in use.

3:25And for now, let me tell you about two major attributes

3:28or things about these two protocols.

3:31TCP is the protocol that cares.

3:34What do you mean, Keith, the protocol that cares?

3:36With transmission control protocol,

3:38if TCP identifies that something was dropped like some packet

3:43or message was sent to the other side but it never arrived,

3:46there was never an acknowledgment,

3:48the Transmission Control Protocol

3:50will, in the background, automatically

3:52identify that it did not make it and will facilitate a reason.

3:56And one of the secrets about TCP of how it's reliable and can

4:00identify that maybe all the messages didn't get

4:02sent is that it has a lot of overhead,

4:05meaning it's sending extra packets to confirm,

4:07did you get it, did you get it?

4:08Yes, I got it.

4:09Good.

4:09And all that extra overhead makes TCP a little bit slower,

4:13but it is reliable.

4:14The other big protocol at this layer here,

4:17at this section of our network protocols is UDP.

4:19And with User Datagram Protocol, there's not a lot of overhead,

4:23meaning it doesn't check to see whether stuff arrived or not.

4:26And as a result, it's not reliable.

4:28Sort of like throwing a brick over the wall and you

4:31hope it lands because there's no acknowledgments.

4:33There's no checking to see whether or not

4:35that information made it to the server

4:38that we're sending the data to.

4:39So in a protocol stack-- a protocol simply meaning a set

4:42of rules--

4:43in a protocol stack or a grouping of protocols,

4:46these are protocols that can all work together

4:48to facilitate communication across the network,

4:51in this case, between Bob and the web server.

4:53So this section right here where TCP and UDP live,

4:56that's called the transport layer.

4:58And I really like the idea of the word layer

5:01because it's just one component in this protocol

5:03stack, a group of layers that work together

5:06to send and receive messages across the network.

5:08Now the good news is that once we have an application layer

5:11service like web services that we're asking for,

5:14those application layer services are

5:16written to use a specific transport layer protocols.

5:19So for web services, they're using

5:21at the transport layer, TCP.

5:22So, in this example, UDP wouldn't be used.

5:25The web service is going to use TCP

5:27for reliable communications.

5:29So in addition to Bob's computer identifying the service

5:31that he wants and also including the transport protocol

5:35that's going to be used based on that service.

5:37Bob's computer also needs to include

5:39the address of the server.

5:40And I'm going to call that right here IP address.

5:44Now an IP address is very similar to an address

5:47that we have in a place that you live.

5:50There's two major parts.

5:51There's the house number, which identifies an individual house

5:54on a street.

5:55And there's also a street name.

5:56And IP addresses are very similar to that.

5:58IP addresses identify a specific device on a network,

6:02like a house number.

6:03It also identifies the street, or the network

6:06address where that host or device is sitting.

6:08And this logical layer or section

6:11where Bob's computer adds the IP address of the server

6:14is called the network layer.

6:19And a good reminder for that is that the IP address identifies

6:22the network where that computer is, along

6:25with the individual host on that network.

6:27Now regarding Bob's request, in addition to

6:29adding the server's IP address to the request

6:32that he's going to send out, he also needs to include,

6:35if it's a local server, the network interface card layer 2

6:39or Mac address.

6:41Now mac is an acronym that stands for Media Access

6:45Control.

6:45And it basically boils down to on an ethernet network, which

6:48is traditionally what we're using in high speed wired

6:51networks, every network interface card

6:53has its own burned in address from the factory.

6:56It's 12 digits long.

6:58Sometimes, it's called a Mac address.

7:00Sometimes it's called a physical address.

7:02And Bob's computer, before it sends out the request,

7:04also needs to include that as part of the request

7:07so that the network can deliver it to the correct network

7:10interface card, which is attached to the server,

7:12so the server can get the message.

7:14And they call this section where we have Mac addresses

7:17on an ethernet network, they call that the data link layer.

7:24And once Bob has collected all that information

7:26and is ready to send his request.

7:28It then get spit out into the network

7:30in the form of individual bits.

7:32The network forwards that to the correct device,

7:34who then receives it.

7:35And if it's a web server and it's a web request,

7:37the intention is for that web server

7:38to respond back to that client.

7:41And the actual sending of the data

7:42back and forth is referred to as the physical layer.

7:46And when we say bits of data, a bit is like a light switch.

7:50It's either on or off, little individual

7:52signals that are being sent one by one across a network.

7:55So as a quick review, Bob's computer

7:57would logically identify, in the browser specifically,

7:59that we're making a request of a web service.

8:01It would automatically associate TCP

8:03as the transport protocol in use.

8:05It would add the IP address of the server.

8:07It would add the Mac address, the ethernet address

8:10of the server.

8:10And then it would send those bits on the wire.

8:13And one of the benefits of chopping these up

8:15into logical pieces like this, these layers

8:17is that it's easier to understand

8:19as we continue to work with and study networking.

8:22It's also a lot easier to troubleshoot

8:25if we know what parts work and don't

8:26work when two computers are trying to talk with each other.

8:29And then if you'll bear with me one more moment,

8:31I want to share with you one more reveal.

8:33And that is this.

8:35In protocol stacks, these protocols

8:37that all work together, one of the protocols stacks

8:39is called TCP/IP.

8:42And that's this one, what we just described.

8:44And it gets that name of the TCP/IP protocol stack

8:46or the TCP/IP protocol suite because of two protocols

8:50that are quite often used, including

8:52TCP at the transport layer and IP at the network layer.

8:57And that's why it's called TCP/IP.

8:59So when somebody refers to a TCP/IP protocol

9:02stack or a network running TCP/IP,

9:04they're really referring to this whole chain of events

9:07with each of these protocols, these sets of rules

9:10playing their respective roles.

9:11And one other thing that's pretty darn cool

9:13is that we also have layer numbers associated with this.

9:16The physical layer, we'll often refer to it

9:17as layer number one.

9:19And the data link layer with the ethernet addresses or Mac

9:22addresses, we refer to that as layer 2.

9:24The network layer where we have IP

9:26addresses, we refer to that as layer 3.

9:29And the transport layer where TCP or UDP is used respectively

9:32based on the application that's being used, that's layer 4.

9:35And the application layer, we just

9:37call that the application layer.

9:39We don't call it layer five.

9:40It's just called the application layer.

9:42In this Nugget, we had the opportunity

9:43to open the kimono a little bit and take a closer

9:46look at the logic in the TCP/IP protocol suite that's

9:49being used when a computer like a client, like Bob's computer,

9:52is talking to a web server.

9:54So my homework assignment that I would love for you to do

9:57is to go back about 30 seconds in this video,

9:59freeze the frame, and I'd like you to draw out that table

10:02that we created together, which will help

10:04you reinforce the concepts.

10:05So please take this opportunity to do that,

10:07and I'll see you in the next video.

10:09Meanwhile, I hope this has been informative for you.

10:11And I'd like to thank you for viewing.

0:00It is pretty darn cool to be able to walk

0:02into a troubleshooting scenario and-- because we understand how

0:06a network operates and how it works--

0:08we can very quickly identify the problem

0:10and hopefully resolve it for our customer.

0:12Well, in this Nugget, we're going

0:13to pick up where we left off in the previous one

0:15and take a look at some additional application

0:17layer services, and also the underlying layers

0:20that make them function.

0:22Let's jump in.

0:23And let's use our scenario here with Bob

0:25right here at computer two and Bob

0:28wants to access a web server.

0:30Now Let's back up just a moment.

0:32When you or I or somebody else tries

0:34to access a web server from the browser,

0:36normally they're going to type in a name,

0:38like the name of the server.

0:39Maybe it's Google.com or whatever the website name is,

0:46and behind the scenes when the types in Google.com com,

0:50somebody--

0:50I'm talking about the computer that Bob sitting at--

0:52that computer needs to figure out

0:54what exactly is the IP address associated with the server

0:59Google.com.

1:00Because computers on IP networks are talking to other IP devices

1:05and so these names are just a convenience.

1:07There needs to be some kind of a translation

1:09or a look-up for Google.com to a corresponding IP address,

1:13and that's happening behind the scenes millions of times

1:16a day on computer across the world.

1:19And in the TCP/IP protocol stack,

1:21there is an application layer or service and that is called DNS.

1:26And that is an acronym that stands for domain name service.

1:30And in effect, DNS--

1:31this domain name service--

1:33what it does, it gives the ability

1:35to give it a name like Google.com

1:37and get an IP address associated with that name.

1:40So that our computer can then try

1:41to connect to that server based on its IP address.

1:45So in addition to web services and file services,

1:49another service that we have in the TCP/IP protocol suite

1:52is the application layer service of DNS, domain name system.

1:56And when DNS was created, it was created to automatically use

1:59the transport protocol of UDP.

2:03So when Bob is sitting his computer

2:05and he types in www.remoteserver.com some other

2:08name in the browser, behind the scenes DNS is being used

2:12and DNS is going to use the transport layer protocol

2:15of User Datagram Protocol.

2:17Now let's also presume that this is the DNS server

2:19that Bob is going to be using behind the scenes

2:21to resolve that name into an IP address.

2:24If this server is running web services and DNS and four

2:28or five other services, if Bob makes a request over

2:31to the server, how is the server going to know?

2:34What you're looking for, Bob?

2:35Do you want DNS services or do you want file services or web

2:38services?

2:39What do you need?

2:40A primary way of identifying the service that Bob is asking for

2:44is to use what's known as a well-known port.

2:47Sometimes abbreviated as WKP, and for application layer

2:52services a lot of them have a well-known port, a transport

2:55layer port, associated with them.

2:57So in the case of DNS, that request

3:00when it goes over to the server is not only going to use UDP.

3:03But it's also going to have a destination UDP port of 53.

3:07Now the only magic of memorizing a service's well-known port

3:11is to see it a few times.

3:12So at this stage of the game, it's

3:14not too important to memorize that a DNS uses UDP port

3:1853 as its well-known port, because if we have access

3:21to a computer and we can use Google, we could find that out.

3:24We could search that very, very easily.

3:26But I wanted to share with you behind the scenes what's

3:28going on.

3:28So in Bob's request, when it's making a DNS request

3:31over to the server, it's going to include the transport layer

3:34protocol of UDP--

3:35based on the application layer service being used--

3:37and a destination port of 53.

3:40Another challenge is that Bob's computer could

3:42be making lots of requests.

3:43And so to keep them straight, Bob's computer

3:45is also going to include a source port--

3:48a source UDP port--

3:49when it makes that request.

3:50And you might ask, OK, well, Keith how

3:52does computer 2 choose a port?

3:54And it just spins the wheel.

3:56So it chooses a port that's currently not in use

3:59on this computer that's greater than 1024.

4:03And it simply starts to use that for this session.

4:05So in this example, let's say that Bob's computer spun

4:08the magic wheel and said, hey, port 58,777 isn't in use.

4:14I'll use that one.

4:15And so it'll include that in the request.

4:17So when the server receives this request,

4:18it would be going to the server on port 53,

4:21where the DNS server is listening and waiting.

4:23And it would also see it as coming from, logically,

4:26port 58,777-- which Bob chose to use when he made the request.

4:32And before Bob's computer sends that DNS

4:34request he's going to have to include

4:36the IP address of the server.

4:37And to make this a little bit simplified,

4:39I'm going to say that the server is IP address B,

4:45and that Bob's computer is IP address A.

4:50So before Bob sends other requests

4:51he's going to include in this request

4:53the destination IP address, which is this guy right here.

4:56I'll just put an arrow.

4:58And Bob will also include his own IP address as the source.

5:01And by Bob including his source address,

5:02it's sort of like a return address on an envelope.

5:04That way somebody, when they get the message

5:06or get the envelope, they can look at the return address.

5:09If they want to respond back, they

5:10can use that return address to respond back--

5:12in this case back to Bob.

5:14And at layer two, the data link layer,

5:16we have the Mac address information.

5:18That's the 12-digit hard-coded addresses

5:21that are built into the ethernet adapters.

5:23And if the computer and the internal server

5:25are both on the same network, Bob

5:27would put his source layer two ethernet address as the source.

5:32And he would put these server's layer two ethernet address

5:35as the destination.

5:37So when Bob sends his request and is trying to resolve

5:39Google.com or some other name to an IP address,

5:42when the server gets it, it will respond back to Bob--

5:45or back to computer two, in this case, more specifically--

5:47with the answer regarding the IP address behind Google.com.

5:51And then once Bob's computer has the IP address for Google.com,

5:55Bob can then choose to connect to Google.com

5:58or whatever website Bob's trying to reach.

6:00And if Bob is using a browser and wants to go to a web page

6:03at Google.com or to another web server,

6:05he would then be using-- or his computer would be using--

6:08for that web request--

6:09he would be using Web services.

6:11Now in the world of IP networking at the application

6:15layer, a major protocol for web services is called HTTP.

6:22And HTTP, the acronym stands for hypertext transfer protocol.

6:27And it is what's used quite commonly for access

6:30to web pages.

6:31So if we're going to www dot anything,

6:33there's a very good chance that our computer behind the scenes

6:35is going to be using HTTP or for security, maybe

6:39HTTPS as the application layer service.

6:42For this example, well imagine Bob is simply

6:44going to a website that doesn't have the security involved

6:48with it, and is just using HTTP.

6:50For web services using HTTP, the transport layer protocol

6:53that's built in to support HTTP is TCP--

6:57transmission control protocol.

6:59And the well-known port that a web server would be listening

7:03on, would be TCP port 80.

7:06So when Bob formulates this request

7:08to go to the web server, Bob's going

7:10to use the destination port of 80--

7:12which the web server is listening on.

7:14And then Bob-- it is very similar to what we do with DNS,

7:16is going to spin the magic wheel.

7:18Find a port that is currently not being used, logically,

7:21on Bob's computer, and use that as the TCP source port.

7:25So let's imagine we use 1,553.

7:29And then for the IP addresses, Bob

7:31would include the web server's IP address here,

7:34his own source address here.

7:36And if they're both on the same local network,

7:38Bob would include his local layer two address,

7:40his ethernet address here, and the servers designation

7:43layer two address there.

7:45And then all of that information as a request

7:47would be sent out, in this case, to the web

7:50server that Bob wanted to go ahead and communicate with.

7:53So let's take a moment and identify what we've reinforced

7:56and discovered in this Nugget.

7:57We've taken a look at two application layer services

8:00in the TCP/IP protocol suite.

8:02One is DNS.

8:03Its intention is to help us discover the IP

8:07address behind a web server name like www.google.com.

8:11The transport layer protocol for DNS is UDP.

8:14The well-known port is 53.

8:17And for web services and the popular protocol

8:19HTTP as an application layer protocol or service,

8:23it uses TCP at the transport layer.

8:26And it has a well-known port of TCP port 80.

8:28Which means that if a web server is running,

8:31it is going to be listening on TCP port

8:3380 for any incoming requests.

8:36And when those requests come in, the intention

8:38is for the web server to respond back

8:40to the client to provide that service-- in this example, web

8:42services-- that the client was after in the first place.

8:46In this video, we took a look at a couple of application layer

8:48services, the transport protocols they use,

8:51and their well-known ports.

8:53In the next video, we're going to answer the question can you

8:55prove that's really happening?

8:57And the answer is yes.

8:58I'll see you in the very next Nugget.

8:59Meanwhile, I hope this has been informative for you,

9:02and I'd like to thank you for viewing.

0:00There is an interesting set of tools that we can use to both

0:04troubleshoot networks and also verify that networks are

0:07operating the way we think they are.

0:09So, in this Nugget, I'd like to introduce you to a couple

0:11of tools, including a protocol analyzer,

0:14which sounds cool and is, and why it's useful.

0:17And also ways to help verify that features and services like

0:21DNS and HTTP are actually working.

0:24So, let's imagine that you and I are working together at a help

0:28desk or a service desk where we take people's calls.

0:31They have network challenges.

0:32And one of our users, Bob, he calls in, and Bob says,

0:35hey I can't open a browser to the server

0:39remoteserver.nuggetlab.com, or whatever site it is.

0:43One of the things that we could do on that computer,

0:45if we go visit him, is on his computer we could get a CLI,

0:49a command line interface, like a command prompt.

0:52And there's command prompts available on Windows,

0:54on Macintosh, or Linux.

0:56And if we wanted to start troubleshooting that,

0:58one thing we could do is we could use a tool called ping.

1:02Now, ping is just a basic connectivity test.

1:05And if Bob was trying to get to www.remoteserver.com--

1:11I'll just make it short here-- or some other website that we

1:14ping and the response comes back,

1:17and it shows us the IP address that it's trying to reach,

1:21we can pretty much rule out DNS as being a primary problem

1:25because whether or not the ping actually functions,

1:27if ping shows us the IP address is 67.83.4.9,

1:32or whatever IP address, we know that DNS,

1:35the application-layer service DNS,

1:37is working because it resolved the name to an IP address.

1:40Or maybe there is a challenge somewhere else in the network,

1:43but with a very quick ping to that name,

1:46we can very quickly see whether or not, based on the results--

1:49whether or not DNS is working.

1:51Another good troubleshooting tip would be, from Bob's computer,

1:54to actually verify and see for ourselves that he is not able

1:58to reach the website that he's trying to reach just to verify

2:01that the problem exists.

2:02Now, another amazing tool that we can use in computer networks

2:06for both learning purposes and for troubleshooting is called

2:09a protocol analyzer.

2:11And what a protocol analyzer can do,

2:13it can capture all of the packets that are being used

2:16and then we can dissect those packets and see the actual

2:19layers.

2:20We can see the transport layer with TCP or UDP.

2:23We can see the Layer 3 information with the IP

2:26addresses.

2:27We can see the Layer 2 information.

2:28And a protocol analyzer is going to rely on us capturing packets

2:31somewhere on the network.

2:32Maybe we're running it on his computer and we're capturing it

2:34here.

2:35Or we're tied into this switch and we're pulling the packets

2:38from there, we're capturing it there.

2:40Or maybe we're capturing the packets in the path somewhere

2:43between Bob and where the final destination is.

2:45But a protocol analyzer is a great way to look

2:48at the packets and see what's going on inside of them.

2:51So without further ado, let me you a quick demonstration

2:54of a protocol analyzer as we look at both a DNS request

2:58and also an HTTP web session.

3:02So I have in this folder here on the desktop some capture files

3:05that have captured various sessions or packets,

3:08and the first one I'd like to show you and walk you through

3:10is the DNS request and reply--

3:13that's when a client was trying to resolve the name of a server

3:16to an IP address.

3:18So it could contact that server based on its IP address.

3:20So, if we open this up, here in the first entry we have the DNS

3:24request, and then we have the DNS reply below it.

3:27And the cool part is we can open up--

3:29in this section right here, we can open up the details.

3:32So, here in the application layer service,

3:33we have the DNS query.

3:35And if we open up that query, this guy was looking

3:38for remoteserver.nuggetlab.com, that was the request.

3:41So that's the application layer information from the protocol

3:44stack.

3:45If we go to the transport layer, Layer 4,

3:48we have information about the transport protocol being used.

3:50Here, it's UDP, and the destination port was

3:53the well-known port of 53 for this request.

3:56If we collapse that at Layer 3, we have the IP information,

4:00including the source and destination IP address.

4:03And then at Layer 2, we have the Ethernet header information,

4:06including the source and destination Layer 2 addresses

4:09involved with this frame of data being sent on the network.

4:12And if we close that packet capture--

4:15so, I'll open up this one for HTTP and we can see it.

4:18So here with this first entry selected the application layer

4:21service is HTTP, the Hypertext Transfer Protocol.

4:25The application layer service of HTTP--

4:26Hypertext Transfer Protocol uses that Layer 4 TCP,

4:30so here's the TCP information, including the destination port

4:33of 80, which is the well-known port that web servers are

4:37listening on.

4:38And then if we collapse that and take a look at the Layer 3

4:41information, the network layer that has the IP information,

4:44and at Layer 2 we have the Ethernet information.

4:47And my first exposure and delight with using a protocol

4:50analyzer was back in the 90s at Paramount Pictures when we had

4:53a client-server application and we were trying to discover why

4:57isn't it working?

4:58Is it the server, or the client that is sending a malformed

5:01request, or not replying to a request?

5:03And we were able to, using a protocol analyzer,

5:05identify where the problem was, talk to the programmers,

5:09and get that network-based application corrected and back

5:11on track.

5:12And before we end this video, let me also show you a really

5:15quick way that we can verify if Bob was having a problem

5:18reaching remoteserver.nuggetlab.com.

5:22A quick way of verifying whether or not DNS is working--

5:24and that is simply going to a command prompt.

5:27So here, I'm going to right-click on the Windows icon

5:29in the bottom left-hand corner, select Command Prompt,

5:31and from the command prompt if we do a ping and then the name

5:34of the server that Bob's trying to reach,

5:36in this case it was remoteserver.nuggetlab.com,

5:41and press Enter.

5:42So that actually worked.

5:44But here's the part regarding DNS because we are pinging this

5:47name, but in the output, it showed us that we were actually

5:51trying to ping this IP address, that implies that name

5:54resolution, in this case, DNS, was working correctly.

5:58Even if the pings had failed, but yet we had an IP address

6:01that it gave us, that would at least tell us that DNS is not

6:04the problem that we need to solve.

6:06It's something else in the network,

6:07and we can leave DNS alone

6:09In this video, we've taken a look at some tools that we can

6:11use to verify network functionality, including ping--

6:14we could ping a name, and if it returns an IP address,

6:17we know that DNS is probably working OK.

6:20We also identified that we could use a protocol analyzer

6:22to collect packets and then take a very detailed look at those

6:26packets.

6:27And that tool will become more and more useful the more

6:30experience and opportunity you have to work in a computer

6:33network.

6:34So, thanks for joining me in this Nugget.

6:36I hope it's been informative for you,

6:37and I'd like to thank you for viewing.

0:00Learning new things is fun.

0:01And oftentimes, if we are learning something new

0:03and we see a couple of different perspectives of it,

0:06it helps it to stick more and be remembered more in our minds.

0:09In the previous few Nuggets, we've

0:11taken a look at the concept of a protocol stack.

0:15And just as a quick summary, with a protocol stack,

0:17we have the application layer in the TCP/IP protocol stack.

0:21We have application layer services, functions, and things

0:24that we want-- things like name resolution with DNS.

0:27That way, when Bob types in www.remoteserver.com,

0:31a DNS server can respond back and say, oh,

0:33that's this IP address, and then Bob can continue on his way.

0:37Or, if Bob wants to go to a web page,

0:39the application layer service is going

0:41to be something like HTTP that's going to be making

0:44that request for the web page.

0:45But those application layer protocols

0:47don't work by themselves, they need a little help.

0:50They need things like transport layer protocols,

0:53whether it's DNS that uses UDP, or HTTP, which uses TCP,

0:58they need to have those associated protocols to help

1:01them get the message across.

1:03And then at the network layer, we

1:04have protocols such as IP version 4 with IP addresses

1:08that are added.

1:09And as we go down to Layer 2, on an Ethernet network,

1:12we have Layer 2 Ethernet addresses that are added.

1:15Then at the physical layer, those messages

1:17are then spit out, bit by bit, over the network

1:20and hopefully, they're delivered to the final destination.

1:23So, what I wanted to do is present a slightly

1:26different way, and a fun way, of talking about that same process

1:29and the protocol stack that you can replicate and talk

1:32to your friends or loved ones about how

1:34a protocol stack operates.

1:36So, we'll start off with a service,

1:38and I use a cup for this-- so let

1:39me see-- make sure I get that in the camera.

1:41There we go.

1:42Great.

1:42So, we have an app or a service at the application layer,

1:45and we're going to choose DNS.

1:47And from our previous Nugget, DNS is used behind the scenes

1:51when Bob tries to go to www.somegreatwebsite.com.

1:55DNS is there to answer the question, what is the IP

1:59address associated with that?

2:00So, let's say for this example, that this cup represents

2:03a DNS request looking for the IP address behind a website name.

2:08So this is the application layer service.

2:10Now, behind the scenes, DNS is going

2:12to be using the transport layer protocol of UDP, User Datagram

2:16Protocol.

2:17So, we're going to add that component right here

2:19and we're going to UDP, we're going to go ahead and put it

2:22like this.

2:23So, the UDP is now going to have the information

2:26on the transport protocol, which is UDP and its ports.

2:28It's also going to have, as its payload, the actual DNS

2:31request.

2:32Now, the transport layer, in this case, UDP,

2:35needs a little help from Layer 3, which is the network layer.

2:39And at the network layer, that's where

2:40we add the IP addresses-- the source IP

2:43address of the client who's making

2:45the request and the destination IP address of the server

2:47we're trying to reach.

2:48So we'll add that on as a separate layer.

2:52So, on the top of the transport protocol, which

2:54is UDP in this example, we'll then

2:56add a header that contains the IP address information.

3:00And then after the IP address is there, we also need to have--

3:03on an Ethernet network--

3:04we need to have the Layer 2 Ethernet addresses,

3:07those network interface card addresses

3:09that are burned in from the factory to those network

3:11adapters.

3:12So to do that, we add another layer of information,

3:15another header, and that's the data link layer, Layer 2.

3:18And in this example, we're using MAC addresses,

3:20the Ethernet addresses on the network interface cards.

3:22And once we've done that, and all that information is now

3:25here and ready to go, we then spit those out

3:28on the physical network, one bit at a time.

3:31And they're sent across the network

3:33and they're reassembled by intermediate network devices

3:35and the final server, who then takes

3:37a look-- oh, this is for me.

3:39It's my address, it's my IP address,

3:42it's UDP port 53 on the server.

3:44Ah, it's a DNS request.

3:46And then if it responds, it builds back

3:49another response that includes the UDP response, the answer--

3:53the DNS answer-- including the UDP protocol,

3:57including the correct IP addresses,

3:59including the correct Layer 2 addresses--

4:01if my cup will release-- there we go, and then

4:03finally those are spit out on the network,

4:05and they're delivered by the network

4:07back to the client, who then peels it apart.

4:10Oh, that's my Layer 2 address.

4:12Oh, this is my IP address.

4:13It's UDP.

4:14It's using the port I did the request on.

4:16And, yay, it's the answer to the DNS request

4:19that that client made a few moments ago.

4:22So that's just a fun way, with some cups,

4:25that we can help represent the encapsulation that

4:28happens all the way from getting an application layer service

4:32and adding the transport protocol, the network IP

4:35address, the Layer 2 information, and then finally

4:37sending it out on the wire.

4:39So in this Nugget, I wanted to give you

4:40a slightly different way of looking at it in a story that

4:43involves some cups to help cement or reinforce

4:45the concept of a protocol stack working together

4:49to allow traffic and messages to be delivered over a network.

4:53I hope this has been informative for you,

4:55and I'd like to thank you for viewing.

0:00When a computer, like this one right here,

0:02is connected to a network with a wired connection,

0:05its network interface card has a 12-digit burned-in address

0:10that the manufacturer of that card gave to it.

0:13In this Nugget, I'd like to chat with you

0:15about some details regarding that layer 2 address

0:18and how you can discover what that layer 2 address is

0:21on this network interface card, whether you're on Linux, Mac,

0:24or Windows.

0:25And one of the curious things about these burned-in layer 2

0:29ethernet addresses that exist here on computer 2 for its

0:32network interface card, here on computer 1 for its network

0:35interface card, the printer's network interface card,

0:38the network interface card that's being used by the access

0:41point-- it has one--

0:42this server as well, it's got one.

0:44One of the interesting things about that address

0:47is that it could have several different names.

0:49And here are some of the names that it

0:51could be referred to as.

0:52That 12-digit address could be referred to as a layer

0:552 address or a physical address or an ethernet address

0:59or a hardware address.

1:00It's all referring to that 12-character number that's

1:02assigned to the network interface card.

1:04Now that 12-digit number on that network interface card,

1:07it is in something called hexadecimal.

1:10Now have no fear, decimal, which we are normal and--

1:14which we normally use is 0 through 9.

1:17It's probably because we have 10 digits and 0 through 9 is 10.

1:20But in hexadecimal, or we can call it hex for short,

1:24it goes 0 through 9.

1:26And it continues on with A through F.

1:30So we could just summarize that by saying

1:32it's 0 through F, which is a total of 16

1:35different positions.

1:36So let's start here on this Windows computer.

1:39Now there's several flavors of Windows,

1:41and there's similar flavors of Windows 10.

1:43And there's also several flavors of Windows Server.

1:45But the concept of the process is basically the same.

1:47We're going to go to a command line interface.

1:50So that may be PowerShell, or it may be a command prompt.

1:54Either one will do great.

1:55On this Windows computer, we're going

1:56to click on the Windows icon in the bottom left-hand corner.

1:59I'm going to type in cmd, short for command

2:01prompt, and then go ahead and launch command prompt.

2:03So here at the command line, on this Windows computer,

2:06we're going to type an ipconfig /all.

2:12So it's I-P-C-O-N-F-I-G space forward slash all.

2:17And the output we're looking for is

2:19the details for ethernet 0 on this specific computer.

2:22So we'll press Enter.

2:23And here in the output of that command,

2:25ipconfig/all, it has the information for ethernet 0,

2:29including its IP address.

2:31That's the layer 3 logical address.

2:33It also has the physical address,

2:35which is the layer 2 ethernet address associated

2:38with this network adapter.

2:40So that is the layer 2 address for this network interface

2:43card on this computer.

2:45Next, let's take a look at the command

2:47that we could use on a Linux computer or a Macintosh

2:50computer to also discover what the layer 2 address is

2:53on that type of system.

2:55So here, we're looking at a Linux-based operating system.

2:57But the commands that we're going to run here on this Linux

3:00system to see the layer 2 address

3:02is the same that we'd run from the command line

3:04interface on a Macintosh.

3:06So we'll go to a command line.

3:08In this case, We're going to launch an application called

3:10Terminal, which will give us a command line interface

3:12on this Linux platform.

3:15And then let me scoot this a little bit over to the right.

3:17And the command we're going to issue is ipconfig.

3:21Now on Windows, it was ipconfig.

3:24And on the Linux and the Mac, it's

3:26ifconfig for interface config.

3:29So will type ifconfig, press Enter.

3:32And so here for ethernet 0, we have the layer 3 address.

3:36That's the IP address, the IPv4 address specifically.

3:39And then we also have the layer 2 address right here.

3:42So this is the layer 2 address or the physical address

3:45or the burned-in address or the ethernet address

3:47that's associated with this network interface

3:49card on this Linux system.

3:51And that command, ifconfig, would also

3:53be the command on a Macintosh that we

3:55could use to determine the layer 2 address on that system

3:58as well.

3:59In this video, we've taken a look

4:00at the characteristics of a layer 2 address on a network

4:03interface card on an ethernet network

4:05and some of the names it goes by.

4:06We also identified a couple of commands

4:08we can use to view that information on a computer,

4:11whether it's Macintosh, Linux, or Windows.

4:14I hope this has been informative for you.

4:16And I'd like to thank you for viewing.

0:00It's pretty darn cool all the work

0:02that goes on behind the scenes when

0:03computer networks are used.

0:05For example, in our previous few Nuggets,

0:07we took a look at the concept of a protocol stack--

0:09how the protocols work together in a cooperative effort.

0:12So for example, if Bob is going to a website,

0:14he opens up his browser.

0:16And his browser behind the scenes

0:18is going to use an application layer service such as HTTP.

0:21Now HTTP gets a little help from its friend the transport layer,

0:25including TCP, Transmission Control Protocol,

0:27and that information is added-- the ports involved

0:30and the details regarding the transport their protocol.

0:32And then logically, layer 3 is going

0:34to add the IP information.

0:36Now let's pause there for a minute.

0:38Whose IP address are we going to put

0:40in that layer 3 header in this information

0:43that we're requesting?

0:44Well, Bob's computer is going to put its own IP

0:46address as the source IP address,

0:48and the server it's trying to reach as the destination IP

0:51address.

0:52So it adds it at layer 3.

0:53And then it hands it down and an Ethernet network.

0:55It heads down to layer 2, which is going

0:57to add the layer 2 addresses.

0:59That's the burned-in network interface card addresses,

1:02Bob's computer as the source, and the server

1:05as the destination Layer 2 MAC address or physical address.

1:08Now let's stop the truck there just for a moment.

1:11How in the world does Bob's computer that's on the network

1:15know what the server's layer 2 Ethernet address is?

1:18Do they have, I guess, a secret handshake or something?

1:20How did they find out?

1:21And the answer to that is a little protocol called ARP.

1:24And that's what I'd like to chat with you about in this video is

1:27how a computer discovers another computer's layer 2

1:30address on the same network using ARP.

1:33So just for a tad of repetition, let's confirm

1:36what we're looking at.

1:37This is Bob's computer right here, computer two,

1:39and this is the server that Bob trying to go to with a web

1:42request.

1:43So computer 2's layer 3 IP address is 10.1.0.10.

1:48That's an example of like its street name and house number

1:51for this computer, computer 2.

1:52And the server, who's also on the same local area network,

1:55its IP address is 10.1.0.111.

1:59And at layer 2, I have their respective addresses

2:02here as well.

2:03So computer two is ending in 77:88:99

2:07while the server's burned-in address, the media access

2:10control or MAC address is ending in 67:83:22.

2:14I'll put arrows down there as well.

2:17So if this snapshot of a request that Bob

2:20is in the process of sending over to server 2

2:22includes the application layer, it

2:24has the HTTP information for web services.

2:27At layer 4, it includes the TCP information,

2:30including the well-known destination

2:31port of 80 for HTTPS.

2:33At layer 3, it includes the source and destination IP

2:36addresses for Bob and the server's computers,

2:38respectively.

2:39And then at layer 2, it's got the Ethernet addresses,

2:42Bob's source Ethernet address as well as the server's

2:45destination Ethernet address.

2:47So this request, before it leaves computer 2,

2:50he has all that information.

2:51And if we interviewed computer 2, and said,

2:53hey, hey, computer 2, how is it that you discovered

2:57the server's layer 2 address?

2:59You have it here in this request you're sending him.

3:01How did you learn it?

3:02And computer 2 would simply say, I did this.

3:05I asked, what do you mean you asked?

3:08Well, if I didn't know what that server's layer 2 address was

3:12on the same local network, I would just

3:14go ahead and send a request, a broadcast,

3:17and everybody would see that broadcast.

3:19And hopefully, the server when it

3:20sees that broadcast would reply back to computer 2

3:23to say, oh, I saw your request.

3:24You're looking for the layer 2 address associated

3:27with my IP address.

3:28Here it is.

3:29Go ahead and use it and let's talk.

3:31And a set of rules regarding how to ask for a layer 2

3:33address for another device on your same local network

3:36and get a response is a set of rules identified on an Ethernet

3:40network as Address Resolution Protocol,

3:43or as his friends call him, good old ARP.

3:46And if the next question on our minds is, hey,

3:49can you show us that?

3:50The answer would be absolutely yes.

3:51I happen to have at my fingertips

3:53right here a protocol analyzer capture,

3:55a packet capture that shows the ARP request and the ARP

3:59response.

4:00So this first entry right here, if we open up the payload,

4:03it's an ARP request, an Address Resolution Protocol request.

4:07And if we expand the payload of this ARP request,

4:10here's what Bob's computer is sending out on the network.

4:13It's sending out information saying, hey,

4:14I'm making a request.

4:16I'm looking for anybody who's currently using

4:18this IP address, 10.1.0.111.

4:21And on every network, there should only

4:22be one device using a specific address.

4:25And it sent as a broadcast, so everybody on the local network

4:28is going to hear this request, and then

4:30the server who owns that IP address is going

4:32to respond back and include its layer 2

4:35information, its MAC address, its Ethernet

4:37address so that Bob's computer can learn that information.

4:40And that reply is right here in our second entry.

4:42So if we click on the second entry,

4:44this is being sent from the server who's saying,

4:46hey, my IP address is 10.1.0.111,

4:49and if I'm not mistaken, you just

4:51asked for my Layer 2 address.

4:52And here it is.

4:54So armed with that information about the layer 2

4:56address of the server, Bob's computer

4:58can now send a packet with all those details, including

5:01the source and destination Layer 2 address,

5:03so this frame of data can be forwarded

5:06to the correct destination on the local network.

5:08As a result of our time together in this Nugget,

5:11if someone comes up to us and says, hey,

5:13how exactly does one computer learn

5:15the layer 2 address of another device

5:17in the same local network?

5:18We know the three-letter answer--

5:20Address Resolution Protocol, also called ARP.

5:23I hope this has been informative for you,

5:25and I'd like to thank you for viewing.

0:00One of the cool results of our time together in this video

0:03is that in the future, if somebody comes up to us

0:05and says, hey, can you tell me about layer two switching?

0:08The answer that we'll have is, absolutely, yes, so

0:11let's use this as the backdrop for this discussion.

0:14This is the icon that represents a network switch, a layer two

0:18switch specifically.

0:19And this switch has five ports.

0:22Now some switches have hundreds and hundreds of ports.

0:24In this example, we're just going

0:25to start with five, one, two, three, four, five.

0:28And then each of those ports, these

0:29are little RJ45 connectors.

0:33That's the name of that typical ethernet connector

0:36that we use to connect to ethernet networks.

0:37And we have a cable that goes to computer two, another one that

0:40goes to the internal server, PC three on port four

0:44to the printer, port five to a router.

0:45And then that router has additional connections out

0:48to other networks represented by this cloud right here.

0:51And when a switch first powers up,

0:53it does not yet know what the layer two ethernet

0:55address is of computer two, or the internal server,

0:58or any of these devices.

1:00Because it's just been powered up,

1:01but one of the cool things about a layer two switch is it

1:05likes to learn.

1:06And a good question might be, well, Keith,

1:08what does this layer two switch like to learn?

1:10Well, it likes to memorize source Mac addresses.

1:14That means if computer two sends data into the network,

1:18and as part of that, it includes its source Mac address, which

1:20is this bad boy right here.

1:22The switch is going to say, based

1:23on that frame of data that just was received

1:26on this port, port number one, because the source address was

1:29this one ending in 778899, I'm going to remember that.

1:32This is a little game layer two switches like to play,

1:35and it will go something like this.

1:36It says this Mac address--

1:38and I'll just put the one ending in 778899 for brevity.

1:43--is reachable out of port number one.

1:46Because I just saw a frame come in on that port, and the source

1:49Mac address was ending in 778899.

1:52So every time a frame enters into the switch,

1:56a frame of data, the switch is going

1:58to add that to a little table it has in memory to remember where

2:02that Mac address lives, which port that Mac address lives off

2:04of.

2:04Let's do it one more time for this server.

2:06This server has a Mac address ending in 678322.

2:10And so when this server sends at least one frame

2:13into the network on this port, the switch

2:15says, oh goody, that Mac address ending in 678322

2:22is reachable off of port number two.

2:24Because I just saw a frame that came in on port number two,

2:27and it had this Mac address was 678322 as the source.

2:31And that process would continue as PC three,

2:34and the printer, and the router, or any other network devices

2:37send a single frame of data into the switch.

2:40The switch is going to add that to its, what's

2:42called, a Mac address table.

2:44Now one of the questions that might

2:45come up as a result of this extra work the switch is doing

2:48is, why?

2:50Why does the switch want to memorize which Mac addresses

2:54are reachable off of each port?

2:56And that's because a layer two switch has the ability

2:59to make intelligent forwarding decisions based

3:02on knowing where the layer two addresses are,

3:05and what ports it can use to reach them.

3:07For example, if this printer sent a packet into the network,

3:10and at layer two, it was destined for the Mac address

3:13of computer two.

3:14It's ending in 778899.

3:17The switch says, oh goody, goody, goody, goody.

3:19I know exactly where that layer two address is,

3:22and it will forward it on its back plane over to that port,

3:26and then deliver it out that port,

3:28in this case, port number one.

3:29And the benefit is the switch didn't

3:31have to forward that out ports two, or three, or five,

3:34or any other ports, except for the port where

3:36it knew that layer two Mac address lived.

3:39So layer two switches that make forwarding decisions based

3:42on Mac addresses, layer two addresses, are referred to

3:45or commonly known as layer two devices.

3:49So here at layer two, the data link layer,

3:51that's a very common device that we're going to have

3:53is a layer two switch that's making those forwarding

3:56decisions based on those Mac addresses.

3:58And also a common way to refer to the data at layer two

4:02is to refer to it as a frame.

4:04So in the world, most people call

4:06that stuff that is coursing through the networks packets.

4:09But if we want to be literal and more granular,

4:12we could as we focus on the layer two information

4:14call that information or refer to it as a frame of data.

4:18So let's imagine that this switch has learned

4:20all the Mac addresses off all the ports, port number

4:23three, port number four, port number

4:25five, with whatever the respective Mac addresses were

4:28that it learned from those network

4:30interface cards that were sending frames

4:32in on those ports.

4:33And so for most traffic, traffic is

4:35going to be switched at layer two

4:37by the layer two switch only to the ports that

4:40need to receive that data.

4:42Now there is a couple of exceptions

4:43where the switch, when it receives a frame of data

4:46is going to forward it everywhere.

4:48Let's imagine that this router is sending in a frame of data

4:51into the network, and let's imagine that it's a broadcast.

4:57So it's a layer two broadcast.

4:59And a layer two broadcast is 12 Fs,

5:02which corresponds in the background to 48 ones.

5:05It's a reserved address it simply

5:07means everybody needs to see this frame of data.

5:10So when the switch receives a broadcast,

5:12the switch is going to forward that frame to every other port

5:16in that local area network.

5:18Because it could be an ARP request or something

5:21else that every other port potentially may need to see.

5:24Another situation that can arise is referred to

5:26as an unknown unicast.

5:28Now a unicast frame means this frame is intended

5:31for one specific Mac address.

5:33However, what if the switch has not yet learned which port

5:37that Mac address lives on?

5:39So in that case, where it receives

5:41a frame that's going to a Mac address

5:43where it has no clue where that is,

5:44it's going to go ahead and flood that frame,

5:48meaning forward that frame to every other port

5:50on that local area network.

5:52So that, hopefully, it will get to its intended recipient.

5:55So my intention for this Nugget is

5:57to have us learn three basic things.

5:59Number one, that a layer two switch dynamically learns

6:03Mac addresses, and what ports are associated

6:06with by looking at the source Mac

6:08address on every frame that comes into the switch.

6:11Secondly, armed with that information, the switch,

6:15if it receives a frame going to Mac address X or Mac address Y,

6:18and it knows where that port is, it

6:20can forward it directly to that port

6:22and leave all the other ports, not bother anybody else.

6:25And the third thing I want to share with you

6:27is that a layer two switch is one

6:28of the most common ways for connecting and grouping devices

6:32together on wired networks today.

6:34So I hope this has been informative for you,

6:37and I'd like to thank you for viewing.

0:00There's a really good chance that the building or office

0:03or home or condo you're in right now has an address.

0:06That way, mail can be delivered.

0:08You can tell people how to get there.

0:09And that address has several things,

0:11including a street name, which is the same street

0:14name that your neighbors live on on that same street.

0:16And you also have a unique house or building

0:18number for your building.

0:20Well, in the world of TCP/IP and at layer 3 specifically with IP

0:23addressing, we also have the concept of street names

0:27and house numbers.

0:28And that's what we're going to take a look at as an overview

0:31in this Nugget.

0:32And let's take a look at what an IP version 4

0:35address looks like.

0:36There's going to be a number, so we'll

0:37go ahead and put a pound symbol representing number, a period,

0:41another number, a period, another number, a period,

0:44and a another number.

0:45So it's four numbers separated by three periods.

0:48And the range for each of these numbers

0:51could be between 0 and 255 at the max.

0:55And if we saw an IP address, it could look something

0:58like this--

0:5810.10.10.

1:01That's an example of an IP version 4 address.

1:04Now the tricky part for a lot of people when they're first

1:07looking at an IP address is to realize that in this address,

1:10there are two--

1:12I repeat-- there are two parts to this address.

1:15One part is the street, also in technical terms

1:19called the network address.

1:21So whenever you hear the term network address,

1:23just think of like a street name for a building.

1:25And the other part that's in this IP address

1:28is the house number or house address.

1:33So as we look at that, are thinking, wait a sec,

1:36let me make sure I've got this.

1:37You're saying that IP address there has two components to it.

1:41There is a network portion, like a street name,

1:44and there's a host address portion, like a house number.

1:47And that's all kind of in there somewhere.

1:49And that's exactly right.

1:51And then we also have a dividing line

1:52that we can draw to tell which is which.

1:55Let's go 10.1.

1:56If the first two numbers represent the street right

2:00here, the dividing line then says the last two numbers,

2:04the 0.10, represents the actual host.

2:07So this is a basic concept of becoming

2:10aware of how an IP version 4 address is,

2:13that some portion on the left-hand side

2:15represents the network or the street name

2:18and the other portion on the right

2:20represents the actual host on that network.

2:23So this IP address of 10.1.0.10, that could be computer 2's

2:26address, 10.1.0.10.

2:29And this internal server, which is on the same network,

2:32is going to start with 10 1 for the same network.

2:34And maybe it's .0.111.

2:37So we could treat this part right here all

2:39as one network, which is the 10.1 network.

2:43And any computers on that network

2:45need to agree about their first two numbers being 10.1.

2:49If we have another network, which we do--

2:51we've got another network up here where

2:54our public-facing servers are.

2:56And maybe this network is going to be the 10.2.

3:00See a different network like a different street.

3:02And then we have individual host addresses.

3:04So maybe this server right here is 10.2.0.50

3:08and this server is 10.2.0.51.

3:13And the key is the network portion

3:15needs to be the same for anybody who's

3:17living on the same network or the same street.

3:18So 10.1 is common for all these devices.

3:2110.2 is going to be common for everybody up here

3:24on this network.

3:25And then the individual hosts are going to have unique host

3:28addresses-- the tail end portion here--

3:30on that network.

3:31And that way, they can communicate with each other,

3:33and we don't have any duplicate layer 3 IP addresses in use.

3:36And if we haven't already asked the question,

3:38let's ask the question right now.

3:39How do we know with this dividing line

3:43if the dividing line between the network portion on the left

3:46and the host portion on the right, how do we

3:48know if it's in the middle or just after the first number

3:51or after the third number?

3:52How do we know?

3:53And the telltale sign, the indicator

3:55that lets us know where that dividing line is

3:58is called the mask.

4:00Now it could be called the subnet mask or network

4:02mask or mask for short, but that's

4:04the 100% job of the mask is to identify

4:08where that dividing line is.

4:10And the way the mask works is this.

4:11If we have an IP address like 10.1.0.10,

4:15which is the IP address down here on computer 2,

4:18if the mask as it's configured with this IP address

4:20is 255.255.0.0, what that means is that the first number

4:29is the network, the second number because the 255 is

4:34the network and where it was zeroed out,

4:360.0, that means that the last two

4:38numbers here as part of the IP address are the host address.

4:43Let's do one more of those.

4:45Let's imagine we have an IP address of 13.4.6.9,

4:51and we have a mask of 255.0.0.0.

4:55Now my question for you based on this example

4:58here is, which part of this IP address,

5:0113.4.6.9, which part going from left to right,

5:05which is the network and which is actually available for host

5:09addressing?

5:09And if you're saying, well, Keith,

5:11based on the logic we just did, because we have the 255 here

5:14in the first position, that means this first number 13

5:16is the network.

5:17And the last three of the mask are all zeros,

5:20and that means these last three numbers are all part

5:23of the host addressing.

5:24And that would be absolutely correct.

5:27Now I've been working with IP version 4 and also IP version

5:316 for literally decades.

5:33Now there's a lot to know about IPv4.

5:35But in this intro, I just want to provide

5:37you a really high level overview of these logical layer 3

5:41addresses, introduce you to IP version 4,

5:44and then in other courses, including

5:46some of the skills related to IP version 4 and IP version 6,

5:50we'll take deeper looks at CB Nuggets,

5:52we'll take a deeper looks at the details and how they're applied

5:55and some of the consequences of using

5:58certain addresses and certain places.

5:59And I'd like to save those more in-depth and lengthy

6:02discussions for some of those other Nuggets.

6:05So in this Nugget, I wanted to introduce you

6:07to the concept of IP addressing at layer 3

6:10to introduce you to the idea that an IP address has

6:13two parts to it.

6:14There's a network portion that is like a street name,

6:17somewhere on the left.

6:18And then there's a host portion, which like a house number,

6:20somewhere on the right.

6:21And the dividing line is identified

6:24by a method called the mask or subnet mask in an IP network.

6:28I hope this has been informative for you.

6:30And I'd like to thank you for viewing.

0:00In this video, I'd like to chat with you

0:02about the concept of IP routing, including

0:05some basic information that every single host

0:08on the network is going to need to be successful to use the IP

0:12network.

0:13Let's use this topology.

0:14And let's pick on Bob, once again down here at Computer 2,

0:18and Bob is on this 10.1 network, and Bob

0:22would like to go ahead and communicate with the server.

0:25So, the server is on the same network, 10.1.0.111,

0:29so if Bob's going to communicate locally,

0:31he can learn the Layer 2 address of the server, forward it

0:34to that server, and they can have a nice conversation

0:37and party back and forth.

0:38Life is good.

0:38But what if-- what if the server that Bob is trying to access

0:43isn't local?

0:44Meaning, maybe it's out here on the internet.

0:46Maybe it's the server on the 67.83 network.

0:50Maybe the IP address is 67.83.12.34 or something else

0:54out here on the internet.

0:55How in the world is Bob going to get

0:57that request all the way out and make

0:59sure it gets to the server?

1:00Well, Bob can't.

1:03Bob can't do the whole thing on his own.

1:05He's going to need some help from a network device that

1:07can move or route that traffic.

1:09In this case, it would be a router, an IP router.

1:12He'll also need to know that he has

1:14a default gateway or a default router that he can use.

1:18It goes something like this-- if Bob is opening up a browser

1:20or trying to reach a server at 67.83.11.22,

1:25the first question his computer would ask is, hey,

1:28is that IP address 67.83.11.22 on my network,

1:32or is it on a different network?

1:34And on Bob's computer, if his IP address configuration

1:37and the mask indicates that the network is 10.1,

1:39he looks at 67.83 and says, well,

1:41that's a totally different network.

1:44What he will do is he will go ahead and forward

1:46the frame at Layer 2 to his default gateway.

1:51So, even though at Layer 3 in the IP packet,

1:54it would say the packet's going to 67.83.11.22, in the Ethernet

1:59frame at Layer 2, it would have the Layer 2 address

2:02of the default gateway that Bob's computer

2:05is configured to use.

2:06In this example, it's Router 1 at 10.1.0.1.

2:09And then, when Router 1 gets it, the story of IP routing

2:13is based on what this router has been

2:15trained to do-- to forward it.

2:17So it's very likely in this topology,

2:19the router would forward it to the firewall,

2:20and the firewall would route it to the Router 2

2:22and Router 2 would route it to the internet,

2:24and the internet would continue to route it

2:25through the internet until it reached

2:27the server at 67.83.11.22.

2:30And to get this ball rolling with IP routing,

2:33we need to have the infrastructure, the routers,

2:35and firewalls and other devices that have all been trained,

2:38or dynamically have learned how to forward packets

2:41to a given destination network.

2:42And Bob's computer needs a few basic things.

2:45Let's list those right here.

2:47And these are great for troubleshooting.

2:48If a computer cannot communicate to remote networks or is having

2:52a problem, we'd want to check 4 basic elements

2:55of the computer's configuration for its network interface card.

2:59One would be, does it have the correct IP address?

3:03So, if our plan is for Bob's computer

3:05to have the IP address of 10.1.0.10,

3:08and they have the first two numbers be

3:09the network and the last two numbers

3:11be the host address for Bob's computer,

3:13we'd also want to verify the mask.

3:16And in that case, the mask would be

3:17255.255, which means the first two numbers are the network,

3:24and then the last two numbers would be 0.0.

3:26And, if looking at Bob's address,

3:28if that address is correct, the next thing

3:30we'd also want to check is, does Bob have configured a default

3:34gateway?

3:34Meaning, who does Bob forward frames to at Layer 2?

3:38What router does he forward the frames

3:39to if he ever needs to have a packet that needs

3:42to reach a remote network?

3:44Remote means, for Bob's computer,

3:46anything that's not on the same network that Bob is.

3:49And so part of the IP address configuration

3:51would be this router's IP address at 10.1.0.1.

3:57And one other component, while we're

3:58looking at the four core elements for IP configuration

4:01on Bob's computer, would be, does Bob have a DNS server

4:05configured?

4:05Maybe the DNS server is a Google DNS server at 8.8.8.8

4:10or maybe it's the internal server at 10.1.0.111.

4:15But if Bob wants the ability to go

4:17to remoteserver.cbtnuggets.com or some other website name,

4:22in the background, he also needs to know

4:25who he can use for DNS, Domain Name System,

4:27to make a request to figure out what

4:29the heck is the IP address behind that website name.

4:32So these are the four core pieces of information

4:35that we would want to verify on Bob's computer

4:37if we were troubleshooting.

4:38One way of seeing all of that information,

4:40plus a little more, at the command line

4:43is the command ipconfig space forward slash all.

4:48And that command is applicable on a Windows computer.

4:51We can also, in the Control Panel,

4:54go to the properties of the network interface card

4:56on Bob's computer, and that's yet

4:57another way we can see how that network interface

4:59card is configured by going through Control Panel.

5:02In this Nugget, we've taken a look

5:04at the concept of IP routing, which

5:06begins with the client realizing it needs to forward

5:09the frames to its default gateway

5:11so that the default gateway, the Layer 3 router,

5:13can continue to forward that packet in the direction

5:16of the final target.

5:18We also took a look at the four key elements on a computer

5:22that we want to check and verify if we're ever

5:24involved in troubleshooting a computer that can't correctly

5:27communicate or function on a network.

5:29I hope this has been informative for you,

5:31and I'd like to thank you for viewing.

0:00In order for a computer to be happy and functional on an IP

0:03network, it needs to have some basic properties

0:05or configuration set up, including

0:07an IP address, the mask, the default gateway

0:10it could use in case it needs to forward packets off

0:12the local network.

0:13And it also needs to know the DNS server

0:16that it can use to resolve or figure out

0:18the IP address behind the name.

0:20Well, if we have to do that all manually, like go to a computer

0:231, configure it, go to computer 2, configure it,

0:26it's not only time consuming, but there's also

0:28an opportunity for us to do a typo

0:30and put the wrong information in.

0:31So in this video, I'd like to chat with you about how

0:33we can automate that process of dynamically handing out

0:37IP address information and information about default

0:39gateways and DNS servers by using a protocol

0:43called DHCP, which is an acronym for Dynamic Host Configuration

0:48Protocol.

0:49It basically is a way to automatically assign IP address

0:52information to computers without having to do it manually

0:55thanks to DHCP.

0:57So in order to take full advantage of DHCP, the Dynamic

1:01Host Configuration Protocol, we're

1:03going to have a couple of pieces in place.

1:05One, we're going to have a DHCP server.

1:08That's a server that's handing out the IP addresses.

1:10And let's go ahead and use this server as a DHCP server.

1:14And this topology, it's a Windows Server.

1:16And then in addition to having a DHCP server,

1:19we'd want to have a plan regarding

1:21what is going to be handed out by this DHCP server.

1:24So let's set this up as our plan.

1:26Let's say that the server is going

1:27to handle IP addresses in the network 10.1.0.

1:32And let's go ahead and hand out .51 all the way through 99.

1:36And that would be part of our planning

1:38to identify how many IP addresses

1:40we intend to hand out or need to hand out and make

1:43sure our pool of IP addresses on the DHCP is big enough.

1:47Another thing we'd want to plan for besides the IP addresses

1:49is the mask that we're going to be handing out.

1:52So if we wanted this portion, the first three numbers,

1:56to be the network and the last number

1:58to go ahead and be the host address,

2:00our mask would look something like this,

2:03which means that the first three numbers of the corresponding IP

2:06address are the network because there's

2:08255's in each of those those positions for the mask.

2:10And the last number in the mask is

2:110, which means the last number here in the customer's IP

2:15address is their host address, very similar to a house

2:17number on a common street.

2:19Now if Bob, who's sitting at this computer,

2:21if his computer gets an IP address dynamically via DHCP,

2:25we also want to provide details, including what default gateway

2:29Bob should use.

2:30So if this is a 10.1 and the router

2:33is at 10.1.01, that's it IP address,

2:36we'd also want to hand out, along with the IP

2:38address, the default gateway that Bob's computer should use.

2:41So in this topology, it would be 10.1.0.1.

2:45And if Bob's computer ever wants to figure out

2:48what the IP address is behind the website

2:50name or some other name, Bob is going

2:52to need to know which DNS server that he should use

2:55or his computer should use.

2:57So we can also hand out the DNS server information

2:59along with the IP address as part of DHCP.

3:02So let's imagine the DNS server we're going to hand out

3:05is 10.1.0.111, which is another local server here

3:09on our network.

3:10And when we're handing out this information via DHCP,

3:13these options like the default gateway the client should use

3:16and the DNS server that the client should use,

3:18those are literally called options.

3:21You don't have to hand that information out.

3:23But that information is going to be really important for Bob

3:25if he wants to be able to communicate and send

3:27packets outside of his local network or do name resolution.

3:31So we'd want to include those options on the DHCP server.

3:35And many times, as you and I work

3:37in a networked environment, there

3:38could be different people with different responsibilities.

3:41So we may need to coordinate if we're the network guys,

3:43we may need to coordinate with the server guys

3:46to identify or confirm the details regarding

3:49DHCP and its accessibility.

3:51So for this discussion, we're just

3:52going to go ahead and presume that all

3:54of this information and the details regarding DHCP services

3:58are configured on this internal server and ready to go.

4:01So our server is ready.

4:02The other piece we need is we need Bob's computer, computer

4:052, to act as a client.

4:07Now this part is really quite simple.

4:10All we need to do is go to the configuration of that network

4:13interface card and tell it that we

4:15want it to obtain an IP address automagically or automatically.

4:19And what that does, that tells Bob's computer

4:22to go ahead and become a DHCP client.

4:24And when that happens, there are four packets involved

4:27between the client and the server.

4:29And those four packets are a discover.

4:32That's where Bob is sending out a broadcast saying, hey,

4:35I'm looking for a DHCP server.

4:37If there's what out there, please respond.

4:39And if there is a server that hears that,

4:41it's going to go ahead and it's going to make an offer.

4:46And that offer is sent back, so the computer 2 can see it.

4:48And in that offer, it's going to include details such as,

4:51hey, here's a specific IP address

4:53that you're welcome to use.

4:55And when Bob's computer sees that response, if it wants it,

4:58it'll go ahead and request it, basically saying

5:01to the DHCP server, hey, thanks for that offer.

5:04I just saw you offered that great IP address.

5:06I will go ahead, and I'll take it at which point

5:09the server is going to send an acknowledgment, basically

5:12an acknowledgment back saying, yep, I totally get it.

5:15You are going to take that IP address that I offered.

5:17And by the way, here are some additional options

5:20that you can go and use with that IP address,

5:23including the default gateway that you should use

5:25and the DNS server that you should use while you're

5:27using this IP address.

5:29And a lot of people remember these four packets

5:31in the correct order by using a little phrase of DORA,

5:35or I guess that's an acronym--

5:36DORA, like Dora the Explorer--

5:39Discover, Offer, Request, and Acknowledgment in that order.

5:43So here's what I'd love for us to do.

5:45This server is all set up with all these parameters.

5:48Let's go over to our client computer.

5:49We'll train it.

5:50I'll walk you through how to train it to be a DHCP client.

5:53And then once we've done that, we

5:54can verify it has an IP address, a default gateway, and a DNS

5:58server that it can use.

6:00And here are our Windows client PC.

6:02There's several ways of getting to the network interface card

6:05parameters for the IP address configuration,

6:07depending on which flavor of Windows

6:09and which flavor Windows 10.

6:11We'd go through control panels.

6:12Sometimes there are shortcuts.

6:14I'm going to right click on the Windows icon

6:15in the bottom left-hand corner.

6:17Click on Network Connections.

6:18And that's certainly one quick way to get there.

6:21So here's our network interface card right here.

6:23So we'll right click on the network interface card.

6:25Click on Properties, and then we'll

6:27go ahead and double click here on IP version

6:304, internet protocol version 4.

6:33So currently, this is statically configured,

6:36meaning it's manually configured with the IP

6:39address, the mask, the default gateway it should use,

6:42and the DNS server we should use.

6:44If we wanted this client to be a DHCP client

6:47and dynamically learn its IP address and the default gateway

6:50and so forth, all we'd do is click this radio button,

6:53obtain an IP address automatically.

6:55And what that means in the background be a DHCP client

6:59and start that discover, offer, request, acknowledgment process

7:02with a DHCP server.

7:04But mostly, I click here, obtain DNS server

7:06address automatically.

7:07And that way, when the DHCP server hands out

7:09the information regarding which DNS server to use,

7:12this client will use that information, as well as

7:14part of its IP configuration.

7:17Once that's done, we'll click on OK.

7:20We'll click on OK again.

7:22And to test this, we just go to a command prompt and issue

7:24ipconfig /all and see the details regarding

7:28the information it just learned via DHCP.

7:31So one way of doing that is to click on the Windows icon

7:34bottom left-hand corner, type in cmd for command,

7:37press Enter to bring up a command prompt.

7:40And then from here, we can type in ipconfig /all.

7:45That's ipconfig /all and press Enter.

7:49And regarding our specific interface

7:51where we just enabled DHCP, it's this one right here.

7:54Here, it receives an IP version 4 address, 10.1.0.51.

7:58It got a mask along with that.

8:00It learned about the default gateway at 10.1.0.1.

8:03And it also learned which DNS server to use at 10.1.0.111.

8:08It's also indicating who the DHCP server is,

8:11and that also is at 10.1.0.111.

8:14This means that our DHCP server is doing double duty.

8:17It's acting as a DNS server, and it's also

8:19acting as a DHCP server.

8:22In this video, we've introduced the concept

8:24of DHCP, Dynamic Host Configuration Protocol, which

8:28can be used to dynamically assign IP address information

8:32and options like the default gateway

8:34and DNS servers to use to computers without us having

8:37to manually go in and configure each and every one of them

8:40on each and every computer.

8:42I hope this has been informative for you.

8:44And I'd like to thank you for viewing.

0:00As we come to the conclusion of this short set of videos

0:03on some of the fundamentals in computer networking,

0:05I've got a question for you.

0:07As you think back on all the videos that we've gone through

0:09together, videos on TCP, and UDP, and the TCP/IP protocol

0:14suite, and how ARP works, and layer 2 switching,

0:18is it interesting to find out how that stuff really works?

0:22See, for me, I just love it.

0:23I mean, once we understand that there's these functions that

0:25are happening inside the computer networks,

0:27if something goes wrong, it's a lot easier to troubleshoot.

0:31If we need to configure something,

0:32we can understand what it is.

0:34And so for those of you who want to reinforce this information,

0:37I've got a couple of tips that have

0:39worked for me over the years, and I'd

0:40like to share them with you.

0:42One is I'd like you to take all the videos that we've gone

0:44through together-- the videos on services like DHCP, and DNS,

0:49and HTTP, or whether it's a video about the basics

0:53of our ARP, how it works--

0:55and I'd like you to find a friend, significant other,

0:58loved one-- whoever will to listen to you--

1:00and explain those concepts to your friend.

1:04And take a few moments to do it.

1:05And what that's going to do-- what it does for me,

1:08it helps me identify, oh, I thought I

1:10understood that, but not quite.

1:12And so maybe you go back, watch a video again,

1:14and then come back, and say, OK, great.

1:16Let me tell you about how ARP works.

1:18Explain the problem.

1:19This computer needs to find that computer's layer 2 address,

1:22and then you teach them about ARP, Address Resolution

1:24Protocol.

1:25So by teaching it or verbalizing it,

1:28it's going to help reinforce those concepts,

1:30and that's a great technique.

1:31The other thing I'd love you to do

1:33if you want to pursue more skills or more knowledge

1:35in computer networking, I've got a few recommendations for you.

1:38I made a list here.

1:40One of the ideas is we can take certification blueprints

1:42from various vendors or organizations,

1:45and look through those blueprints at the items

1:47that they want us to learn or study, and then learn them.

1:50For example, A+ is a great, entry-level foundation

1:55certification that has a lot of topics,

1:57including computers and networks,

1:59that would be a great place to reinforce the skills

2:02we've taken look at in these videos.

2:04Another video series, another course,

2:06would be Network+ also from CompTIA which focuses

2:10on computer networking, and that is great.

2:13So once we see something once, and then you

2:15see it again, and go into a little bit more depth,

2:18the more we can reinforce that knowledge.

2:20And it's a lot of fun every step of the way.

2:22So A+ first.

2:23And if you're focused on networking,

2:24just the networking portions there.

2:26Whatever is interesting to you, go for it.

2:28And then CompTIA's Network+, which is fantastic as well.

2:32And then another-- if you want make a career in computer

2:35networking or really confirm your understanding of how

2:37it works, some of the big boys on the network side

2:41are Cisco Systems.

2:42And so Cisco Systems has some certifications

2:45as well regarding routing and switching.

2:47And one of those CCENT--

2:50CCENT.

2:52If you get that cert, it's half of a bigger CCNA.

2:56So the information details for getting that certification

2:59from Cisco is on their website at cisco.com.

3:03But those core CCENT and CCNA routing switching

3:08certifications are really a good baseline along with Network+

3:13are really good baseline for the fundamentals.

3:15And then from there, you can leverage that knowledge

3:17and continue growing, and learning,

3:20and advancing yourself and your skills

3:22as you pursue a job or a career in the world of IT.

3:25Also, as far as finding work, I have loved search sites

3:29for jobs.

3:31monster.com happens to be one of my favorite.

3:33This morning, I went to monster.com.

3:35I put in network technician.

3:38I put in California.

3:40I put in my zip code.

3:41I'm in Nevada.

3:42I put in a few other locations.

3:43And there are dozens of jobs for network technicians.

3:47And so I looked through the requirements.

3:49I thought, yeah, those are all reasonable expectations

3:52for a network technician.

3:53So if we're brand new--

3:54let's say we're studying.

3:55We allocate 30 minutes a day to studying and practicing.

3:59That's fantastic.

4:00And then measure that.

4:01Make sure you're doing that with that work.

4:02So one of the things I did is I started my Cisco training

4:05as far as learning Cisco Systems, and networking,

4:07and switching, and routing back in 2000--

4:10I take it back.

4:101999-- that's when I started.

4:14And I set a huge goal for myself.

4:16I learned about this thing called a Cisco Certified

4:18Internet Work Expert from Cisco Systems, which is way the heck

4:23up there as far as hard to get to.

4:24It involves a lot of little steps to get there.

4:26I set that for a goal.

4:27That was part of my 10 year goals.

4:29And then in 2000--

4:30I'm sorry, in 2000.

4:32So 1999 is when I started.

4:34In 2000, when I started prepping, I got serious.

4:38And I said to myself, I'm going to prep four to five days

4:41a week about four hours a day.

4:43And this in addition to my normal work.

4:46And I did that for eight months.

4:48Now, one of the benefits of taking small steps--

4:51in those cases bigger steps--

4:53was I went through and I got my lower-level certifications,

4:56than my professional-level certifications.

4:58And then with the additional practice and that eight months

5:01of really hitting it hard, I got my first CCIE--

5:04Cisco Certified Internetwork Expert certification in 2001.

5:09And I passed on my very first attempt.

5:11And a big part of that is a gentleman named Ed--

5:14Ed with the last initial of a Y. And Ed and Í were study

5:17buddies.

5:18He was, I think, in Arizona at the time.

5:20And we would study, hands-on practice,

5:23looking things up, studying, making sure we

5:25knew we could do the practical exam.

5:27And I'm not sure one quick story, and then we'll be done.

5:31It was like, maybe a few-- a week

5:33or two before a final exam-- our exam at Cisco Systems.

5:36I took mine in San Jose, where you fly out.

5:38In those days it was two days long.

5:39You had to configure, and verify, and everything else.

5:42And about two weeks before that final test,

5:46Ed said to me, Keith--

5:47that's what he called me.

5:48Keith, how are you doing on voice over IP?

5:51I said, you know, I'm just so tired of studying.

5:54Get the smallest-- world's smallest violin.

5:56Eeeee.

5:57I'm so tired of studying.

5:59I've been studying for so many months, for so many hours.

6:03I just-- I think I'm going to just peruse that and not

6:06really study the voice over IP.

6:08He said, dude, that wouldn't be a good move.

6:11You need to study that because if you get that,

6:13it's going to be critical for you passing.

6:15Everything is critical for passing.

6:17You have to get a certain level of points in the configuration

6:20within a certain time period.

6:21And so I took another deep breath, and I went

6:24and I studied voice over IP.

6:26And one of the last tasks on the first day of the certification

6:31was to have one phone when you pick it up

6:34to have PLAR, which is Private Line Automatic Ringdown.

6:36You pick up one phone, and it makes the other phone ring,

6:39and it's a voice over IP path between them.

6:41And I tell you what--

6:43Ed, you know this, and I'm sharing this with the world.

6:45Having accountability and having someone encourage

6:48you every step of the way is so important

6:50because that was one of my final tasks on the first day.

6:53And I was flying.

6:55And I was running out of time.

6:57And I was flying.

6:58I saved my config on all the switches and routers.

7:01I picked up the phone hoping that the other one would ring,

7:04and it rang.

7:05And the proctor was right there, and she saw it.

7:07And I thought, ah, there's a chance

7:10I could pass this first day and go

7:11to the second day, which I did.

7:13And I'll save that for another story for another day.

7:15But the key is rehearse and practice what you're learning.

7:19Teaching it to others or explaining it to others

7:21is a great way to help confirm your understanding.

7:23Practice wherever you can with the hands-on.

7:26Use job search sites to see what's being looked for.

7:29And if you don't have those skills,

7:31go ahead and identify those as skills that you

7:33want to develop and work on.

7:34And then have accountability on the small tasks

7:37or the big tasks that you want to accomplish.

7:40Hold yourself accountable and have somebody else

7:42hold you accountable with love to help

7:44put that positive pressure so that you'll

7:46spend a little bit of time every day

7:48or every week practicing, or learning, or studying.

7:51And, my friend, it is possible to go step

7:54by step in the direction of your goals and get there.

7:57And it's amazing what can be accomplished

8:00with just small consistent efforts over time.

8:03So if a career in networking or that

8:04involves networking is in your future, I welcome you aboard.

8:08It's been fantastic for me and continues

8:09to be as I work here at CBT Nuggets.

8:13So I look forward to seeing you in future videos

8:15and future training that we can enjoy together Meanwhile,

8:18I hope this has been informative for you,

8:20and I'd like to thank you for viewing.