Meet Your Network – Devices and Roles

0:00Hello and welcome. My name is Keith Barker, and a lot of times I see something new like, Oh, what's that? Or what's that? Well, in this set of videos, we're going to play that game of what's that regarding network devices and logically what they do in the network. So I'm glad you're joining me for this journey. And I'll see you in the very next video.

0:00Every network from a two-room office to a global enterprise is built on the same handful of devices and each type doing one job really, really well. So before we get into configuration and troubleshooting and protocol work that we're going to have in this course, we also need to be able to look at a piece of gear and know two things instantly. Number one, what is it? And secondly, what job does it do? And that recognition is what lets everything else in this course make sense? Because we can't really troubleshoot or understand a switch to router connectivity if you don't yet understand what a switch is for versus a router. So in this skill, we're going to build that foundation. We'll take a look at the logical representation of different pieces of network gear, and I'll also show you some examples of physical ones as we go through.

0:50And in this overview, let's start off with the graphical representation of those devices, and then we'll dig into each one as we go through the skill. So this represents an end device. So there's this one right here, like a PC or a server or a device that is logically connected to the network. Think of it like the reason we have a network is for the devices that connect to it. So here's the PCs, and then this is a voice over IP telephone. It works like a normal telephone. You pick up the handset, you dial, but behind the scenes when we speak, which is done in analog, like I'm doing right now with you, behind the scenes, it takes the voice that we're speaking, converts it and digitizes it so it can be sent over a digital network. In this example, it's a network based on the protocol called Internet Protocol, or as his friends call it, IP, where it's taking the data, packetizing it, and then shipping it through the network.

1:41And the next device here is called a Layer 2 switch. We'll take a closer look at why it's called Layer 2 in depth in the next skill, where we took a look at models. And this is a graphic for a Layer 2 switch with arrows going left and arrows going right. And its primary job in life is to forward data back and forth between devices on the same network. For example, maybe between PCA and PCC, the switch would be used to forward the data back and forth on that same local network between those devices. The next device in our topology right here is an access point, or as his friends call it, an AEP. And when the access point, you can think of it like maybe like a walkie talkie or something that can both send and receive over the wireless network. So this allows a wireless client like this device right here to go ahead and get access to the physical network through the access point, because the access point is effectively acting as a radio tower for the Wi-Fi network for the wireless network. And the next we have the icon for a typical IP router. Think of a router like a device that wants to move data between two different networks.

2:49So over here, if this was one network, we'll call it network A, and this interface off the router is network B, and this network interface over here off the router is network C, the router can logically route traffic between different networks. So if PCA here wanted to talk to the server, that traffic would not only go through the switch, but also be routed between network A over to network B. So the traffic could go between the PC and the server. So let me clean that up a little bit and let's continue with our icons. So here we have yet another layer two switch. So it's going to forward traffic between devices down here on this network. And then over in this direction, we have a firewall and the NGFW is an acronym for next generation firewall or NGFW for short. And sometimes that can be simply referred to as a security appliance. And based on the type of firewall and how we have a setup, it could be doing traditional firewall services, or it could also add some additional features like intrusion prevention. They call that an IPS intrusion prevention system, which basically says it's looking at all the traffic going between, for example, traffic going this way and traffic going this way. And if it doesn't like what it sees, it can go ahead and stop that traffic in its tracks. So firewall generally has an attitude about security and usually it's pretty

4:07strict. And for connectivity to the internet, we may have a service provider. That's SP for short, who's an internet service provider who is providing us access to the internet. So they may actually have an ethernet switch or device on-prem at our location, or in a smaller environment, we may have a cable modem or some other device that can be terminated here. For example, this topology at the firewall and the other end goes out to the service provider, which allows traffic out to the internet. And then one last device here that I'd like to mention in this overview is a wireless controller. So a wireless controller does this for a living. It is a wrangler or a manager of access points. So most companies don't just have one or two access points.

4:51Many companies have hundreds of access points across various locations. So regarding access points and working with them, we can use a wireless controller. So effectively it's the manager of our access points. So when clients connect, they logically connect to an access point, that's the radio part, but the traffic is then forwarded down to the controller who's then enforcing policy and how to forward that traffic onto other points in the network. So when you see the concept of a controller, think of it as a manager that is in charge of something else. So in this case, a wireless controller is in charge of managing the wireless access points.

5:25I also thought it'd be important to have this graphic here, have this representation here. This represents a protocol stack. Now protocol is a fancy word for a set of rules that we use in networking today. And this represents logically how some of those components fit together. And we'll have a deeper dive into this protocol stack in the next skill. But as a teaser for that, a switch as it's making forwarding decisions between devices in that same local area network right here that operates at layer two, and that's often why it's called a layer two switch, because it's making forwarding decisions based on that information here in this section of the model. Where a router is making forwarding decisions between different networks, it's considered to be a layer three device. And that's why I have here a layer three router. So as far as this graphic over here goes, I just wanted to introduce it. And again, in the next skill, we'll take a deeper dive into that and what it means and why it's important for you to be aware of it.

0:00In this video, I'd like to actually do three things. I'd like to talk about PCs as devices on the network, voice over IP telephones, and also a layer two switch. So a few decades ago, somebody came up with the idea of having digital devices for telephones. And that way, you and I could pick up a handset, speak into it, and behind the scenes, you'd be digitized and then sent over the network. So maybe we have a voice over IP telephone here and maybe there's another voice over IP telephone here. And that way, the person here could pick up the handset and talk to the person here, just like a normal telephone call.

0:32But behind the scenes, all that data is being digitized and sent here in this example within the same network. So this is all for this demonstration. This is all going to be one network. We'll call it Network A. So what the switch does, it has what's called a Mac table. Has nothing to do with Apple products, but the Mac in all uppercase stands for Media Access Control. And each network adapter, which is the acronym NIC for network adapter, has its own unique Mac address. Think of it like a mailbox with a lot of slots in it.

1:05So you have slot one, two and three and four and five and six and seven and eight. Let's imagine you have eight neighbors. They all come to this mailbox and they all have an assigned their own unique number in that mailbox system. However, in this case, the little network interface cards on each device, including all the PCs, also the voice over IP telephone has one as well. They have their own Mac address and the switch builds a table of those Mac addresses. So if you have device X here who is trying to talk to device Y as that data goes into the switch, the switch takes that data and then forwards it to the right port associated with Y's Mac address.

1:41So that's the major purpose of a layer two switch is to make those forwarding decisions at very high speed inside of a given network. Let me also chat with you about how these are physically connected. So here we have the PC, which could represent any end device with an Ethernet port. So those are called little RJ45 adapters or ports that they have. And so we take an Ethernet cable and go from that PC to another little RJ45 jack on the voice over IP telephone. So on the telephone, this jack would be labeled, for example, to computer.

2:13So, you know exactly where to plug it in and then have another jack over here or it could be right next to it, but it could be labeled local area network. We'd plug that one into the actual switch. So the switch is memorizing on whatever port that is where we're plugged in. It knows about the Mac addresses for the phone itself. It also has all the Mac address for the PC. And so if any data comes in that's destined for either this PC or for this phone, the switch knows exactly how to forward it based on that Mac address table. So I like to do two things.

2:44Number one, I like to show you some physical representation of this gear. And then secondly, I'd like to share with you the Mac address table that the switch is using to make forwarding decisions inside of this network. So let's begin with the switch. So this is a very small, it's an eight port Cisco catalyst switch, and it has these RJ45 connectors on it right here. So this RJ45 connector is for the console. So we can connect to it and actually start the managing of the switch before we set up with an IP address. And then this port over here can either take an RJ45 Ethernet cable or it can take what's called an SFP adapter, which lets you plug it in.

3:21And then you can go ahead and use fiber connections to this device. But in any case, this is a Cisco catalyst switch. So I'm going to take an Ethernet cable right here. So an Ethernet cable has eight wires inside, four pairs of wires. So I'll go ahead and plug it into this port right here with a click. And boom, we're now connected. So we can connect here over to our IP telephone. So let me set this over here a little bit. And let me bring in the IP telephone, which is right there. So this is an IP telephone.

3:52And on the back, it's got two ports. They are right here. One says to network and the other says to computer. So the one that says to network, we would use the other end of the cable and plug it into that port right here. Just like that. Now, normally, the switch would not be in the physical same location, meaning it wouldn't be right next to the IP telephone. So this could be in a wiring closet. Then it could be a cable run to the floor, to the ceiling, then to a patch panel in the office, and then to this port here on this IP telephone. Now, the second port, we'll get another cable and I'm going to use a blue one.

4:22So the actual color of the cable is not too important because it's the standards regarding how the cables are made. So there's another Ethernet cable with an RJ45 connection. Also, as far as the number goes, it just happened to be the number they assigned to this type of port, to this type of connection. And that's why it's called RJ45. When it was created and designed, that's what they called it. So that's why we call it that today. So for this cable, then this would go ahead and connect to our PC. So I'm going to go ahead and set this up, meaning set it up right. And I take this blue cable and connect it over to the PC.

4:54So here is a tiny computer and it'll do. So it has two Ethernet ports, network adapters built into it. So I'm going to go ahead and take this one on my right and plug it in. And boom, there's our connectivity between the PC to one port on the IP telephone and then the other port on the IP telephone goes to the switch. So that's the physical connections there. And now let me also share with you what the MAC address table might look like on a Cisco Catalyst switch. And to do this, I'm going to use a terminal emulator. That's a fancy way of saying a program that lets you logically connect over that device.

5:29So I have a cable that's going from my management PC right here over to the console port on another switch here in my office. So here, connected on the console port of this switch, I type in show MAC space address dash table, press enter. And actually, let me limit that to the dynamically learned MAC addresses. So use this command show MAC address table dynamic. We'll focus on the actual syntax of things later. For now, I just want to share with you that this switch knows about all of these MAC addresses right here.

6:01It has dynamically learned them. So this layer two switch, if it gets data in and it sees that it's destined for any of these MAC addresses here, these layer two MAC addresses, it knows how to forward them. So it looks like most of these are reachable off of gig zero slash one over here and that this one right here is reachable off of FAA zero slash eight. So the purpose here with a layer two switch is to do forwarding in the same network based on a MAC address table. Another way of thinking about a switch and how it forwards is thinking about having one big room.

6:35So this is our big room right here. And we have a lot of people in that room. And that's going to be represented by devices that are connected to various ports on this switch. And if there's data that's destined to any one of those layer two addresses, for example, let's say we have a device here that is trying to communicate with this MAC address that's living off of that port. The switcher receives that data comes in here, looks at the tables, says, Oh, I know how to forward that. And it makes a forwarding decision and forwards that data only out this port.

7:05And that way, this device who is intended for receives that data. So the layer two switch, think of it like one room, one giant room where it's making forwarding decisions within that room or aka within that network. However, to move data between two different networks, like from network A to network B, we're going to need a different device. And that device is called a router. And we'll take a look at that in the next video.

0:00So our next device is the Layer 3 router, and here's the icon for that. And I have been working with Cisco for more than 25 years. I'm a double CCIE. And I remember it was like probably two decades in, I realized I'm drawing the router symbol wrong. I used to draw it like this, like that. But it's really like that with two pointing in and two pointing out. Although that doesn't matter. People pretty much got what I was talking about. But that's the actual icon that represents a Layer 3 router. So let's talk about what a Layer 3 router does.

0:30Imagine if we had a router, it had three interfaces, interface one and two and three. Those represent from the router's perspective, three different networks. For example, network A over here, network B over here, and network C over here. So when the router gets data that comes into one of its interfaces, the router is going to look at the destination like, okay, what destination network is this data going to? Is it going to network B or network C? And it consults its routing table. And that's a Layer 3 routing table, aka right there in our protocol stack.

1:03So the routing table simply has information on how to forward. So if a packet comes in, data comes in, that's destined for a network C address, the router says, oh, network C is reachable out this interface, and it can forward out the correct interface to forward that packet on its way to its final destination. Or if that traffic was trying to go out here to the internet, we'll call it network X. Based again on the routing table, it could say, oh, to get to X, my interface I'm going to use is three, and the next device I need to forward to in the path is this firewall.

1:33So it forward over to the firewall based on its routing table, and then it'd be the firewall's responsibility to take the next logical step. So while Layer 2 switches forward data between devices in the same local network, a router is going to forward data based on its routing table between different networks. Now, one of the questions that might come up is, well, how in the world does this router get data that needs to be forwarded or routed? And the answer is our clients have what's called a default gateway configured.

2:03Let's imagine the default gateway that all these PCs have been configured with is let's say 10.10.10.1, just an example that's an IP address on this interface. So when these PCs need to forward data, for example, to network X, which is not here on this local network, this is network A, they would forward that traffic over to the default gateway. And then the default gateway would look at the destination, which is X, look at its routing table, and then make a forwarding decision based on its routing table. So the clients are forwarding it to that next device.

2:35Sometimes it's called the next hop. It's referred to as the default gateway on most end devices. And that's how the router would receive it to make a decision on forwarding. So now that we've taken a look at the purpose of this Layer 3 router to route between different networks, let's take a look at what one physically looks like. So here's our switch from the previous video, and let's go ahead and take a cable here, and we'll plug it in. It's just an ethernet cable with RJ45 connectors, and then we'll plug it into a router.

3:05Now, routers come in different sizes, so do switches. A lot of them are 19 inches wide. They go in a 19 inch rack, and these are smaller versions of those devices, but the logic is the same. So whether you see a router for a small office home office or a router for an enterprise, the logic is the same. A router is routing between two different networks. So we could go ahead and plug into one of these ports here. So this is our switch. Here is the router. And then for the next connection that goes out in our topology to the firewall or down where the server is, we'd use another cable to go ahead and connect to that next device.

3:41And from a routing perspective, let me share with you what a routing table looks like. And here again, my purpose is just to share with you the concept of a routing table. We'll take a look in other skills at how to interpret them and read them. So if we do a show IP route on this Cisco device, and here it's showing us the routing table. So if this device received a packet, received data that was destined to, for example, the 23.1.2 network, it would know exactly how to forward that based on its layer three routing table.

4:12Again, routers are connecting and forwarding traffic between different networks. For example, between network A and network B. And if we go back to switches, switches are forwarding at layer two within a given network. So now that we've taken a look at the icon for a router and also a physical representation of one and also what the routing table looks like, in the next video, let's move our attention to a security appliance like this next generation firewall. So we'll do that in the next video and I'll see you there in just a moment.

0:01So now in this video, let's draw our attention to the next generation firewall. And for this firewall, if it's called a next generation firewall, it means it has some special abilities. Things like analyzing the traffic at a very significant level, just to make sure that there's nothing harmful going back and forth between it. So if a user, for example, right here is going out to a website and tries to download something that has malware in it or a virus, our intention is that the firewall or this appliance, the security plans could identify that as a problem and then stop that return traffic from coming back in, thereby preventing the client from getting a file that has malware in it.

0:40So some of the things that the firewall could do would be intrusion prevention services, looking for naughty behavior or looking for viruses or malware or inspecting other protocols that go through looking for things that are mischievous. So DNS is a very common protocol we use to figure out, OK, what's the actual address behind my favorite server's name? And so if we have some DNS traffic that is not correct or is being manipulated by an attacker, the firewall should be able to identify that and then stop that traffic in its tracks.

1:13And in a Cisco environment, that would be the Cisco secure firewall. And it used to be called firepower. So we might see some of that reference still in older documentation. But Cisco secure firewall is the current terminology for it. So to manage our firewalls, we're going to use some type of a controller. And that controller in the world of Cisco is called a FMC or the Firewall Management Center, which used to be called the Firepower Management Center. In any case, we use an FMC. I would log in here and then we can control the policy on dozens or hundreds of firewalls.

1:45And that way we can manage them better. So let me give you a representation of what a physical firewall looks like. And then I'll show you some logic in the interface of a Cisco secure next generation firewall. And here is our next device. And it also has a lot of RJ45 ports on it as well. And again, they make big firewalls that fill up a 19 inch rack and they make smaller ones like this. And so the cabling would go from the switch over here to the router and then from the router for another port over to the firewall.

2:15So just by looking at the back and looking at the ports, you can't always tell what a device is. We might have to refer to the actual model number just to confirm. Is it a router? Is it a switch or is it a firewall? So this represents the login for the FMC, the Cisco Secure Firewall Management Center. So I will put in my credentials and log in. So it lands me here on the summary dashboard. If we went into devices and we clicked here on device management, that would show me the two firewalls that are currently under the management of this management center.

2:47So I have firewall one and firewall two, and they're both using a security policy, which implements the next generation firewall features. So if you go to the firewall policy that they're both using, it's controlling what traffic can go through. And if we grab one of these rules, it's also showing us some additional features associated with this rule. So we have a IPS policy looking for bad traffic, malicious traffic going through. We also have a file policy looking for malware. And so as traffic goes through, if there's something that shouldn't be allowed through, it'll stop it. So if we go to analysis and malware events, this is a test file that I used a few times just to verify that the next generation firewall could not just identify that that traffic was trying to go through the firewall, but also go ahead and stop it.

3:28So one way of thinking about a next generation firewall is thinking of it like a network device that has a really strong opinion about what's okay or not okay. And that opinion is influenced or configured by us, the network engineers, who actually configure that firewall. And that's why it's always important to follow best practices. Now, another thing that's important to know about a firewall that's here on our network, for example, between this router and our service provider over here, one thing to be aware of is that it can be deployed a couple of different ways.

4:00We can deploy it so it looks like a layer two switch. So it effectively is the same network on this side and this side, and it just lets the traffic go through, but it's still analyzing all of it. Or we could have it configured as a layer three router, in which case this would be, for example, network C, and over here could be network D with its two interfaces. So when you see a firewall, it depends on how it's configured, whether it's being used as a layer two switching device or a layer three routing device. But in either case, it's able to implement with the right configuration, the security policies and services to help control traffic going through the network.

4:37And before we get to the edge here and start talking about our connectivity to the Internet, what I would love to do is in the next video, focus our attention on this access point right here and this wireless controller right here. So I'll see you in the next video for exactly that.

0:00So wireless, if you haven't noticed, is a pretty big deal. And on local area networks, we use something called Wi-Fi, which is a representation of a whole bunch of standards that simply make it work. And the thing about standards and protocols and rules is that if you have two different vendors and they're both following the same set of rules or protocols, those devices should be interoperable. So for Wi-Fi and wireless networking, for wireless clients, they are coming from a large spectrum of manufacturers. Anybody who makes a PC, for example, is very likely going to make a device with a wireless network interface card, which also has its own address on that interface card.

0:39And then it's going to interact with a radio that logically connects it and allows it to send information back and forth between it and this device right here, acting as a radio for that wireless network. And then this wireless access point, the fact that it's called wireless is only for the radio part because it is hardwired into the switch as well. So that's how the wireless client effectively gets access to the physical network is via the access point they're associated with. And in most networks, we have lots and lots of APs. So instead of having to manage them one by one by one by one by one and setting them all up that way, instead, what we can do is manage them as a group.

1:17And we do that by hiring a manager. And that manager is the wireless controller. So you and I would log on to the wireless controller. And then from there, we could go ahead and interact with and manage the access points which have been associated with and assigned to this controller. So let me go ahead and show you some physical representations of both access points as well as a wireless controller. So as a reminder, we have our switch right here and then the router and then the firewall. And so I'm going to introduce here a wireless controller.

1:48Now, this is a really old one, but it still functions. So this is a wireless controller. And notice it also has some Ethernet ports. So what we do is take one of those ports and physically connect that into the switch. So now our wireless controller has access to the physical network and we do a similar process for the access point itself. So let me bring in an access point. And here is an example of a Cisco access point. So this would go on the wall or the ceiling based on the specs and the radio signals based on this type of access point and the back end.

2:21We have some ports. So we have a console port we connect to. It kind of looks like it is an RJ45 feeling port, but this is used to connect directly to this access point from like a terminal emulator. So we could go ahead and get right to the meat of the matter if there's a problem or we're initially setting up this access point. And then we also have an Ethernet connection right here. So the Ethernet connection here, we go from this port over to our switch. So let me add a cable for that. So I just happen to have a green cable. I'll use that. I'll plug that into the Ethernet port there and put the other end of that cable into our switch.

2:52So this green cable is very likely to go from a switch in the wiring closet through a run in the ceiling or the floor until it hits the access point right here. And also because we have lots of access points and not a ton of controllers, the controllers usually will be in a separate network. And so the actual connectivity between the access point and the actual controller can actually be routed. And it doesn't have to be on the same local network like network A or network B or network C. We can have that traffic forwarded through a layer three router between the access point and the controller.

3:24Now, another interesting aspect regarding an access point is it needs power. So if we had an external transformer, we could use that and plug it in right there for power. However, another really cool benefit of using an access point with a special switch that can support it is using a feature called P-O-E, which is power over Ethernet, which means over this green cable, we're not just delivering the data signals for this access point for clients who associate with it and want to connect to the physical network, but we're also on the same cabling providing power to this access point.

3:56And that feature from the switch's perspective is called P-O-E or power over Ethernet. So it just so happens here in my lab, I have a IP telephone that's connected to a powered on switch. And so the one we just looked at wasn't powered on, so it can't deliver power itself. But let me show you from the command line interface, the CLI for short. Let me show you what that looks like from a layer two switch that's providing power over Ethernet to an IP phone. So I've connected to the console port on this switch, on this CLI switch. So we do a show power in line and press enter.

4:28That's first of all, confirming a few things for us. Number one, it can deliver up to one hundred twenty four watts of power. And we have currently fourteen point four watts in use. And that's being delivered right here off of this port to an IP telephone, which is a model ninety nine seventy one. And just for grins, I just plugged in the access point to port seven here. And so here in a moment, because it's also getting power, if we do a show power in line. So here's now showing that I've got fourteen point four watts of power being delivered to this IP telephone and I've got fifteen point four watts being delivered to this thing and that's the access point that I just plugged in.

5:06So now we've taken a look at a physical wireless controller. We've also taken a look at one example of an access point and also talked about how we can deliver power from a P.O.E. compatible switch. We can deliver power to devices that can receive power via P.O.E. power over Ethernet. So in our example, we're delivering power to the access point and also delivering power to this voice over IP telephone. And the benefit of that is that we don't have to find outlets in the ceiling where these access points are or have an extra transformer in the office where an IP phone is because we can deliver that power for those types of devices right from our power over Ethernet compatible switch.

0:01In this video, I'd like to chat about this connectivity right here, which connects from the edge of our networks to the Internet. And that's going to be done through some flavor of an ISP, which is an acronym for Internet Service Provider. Somebody who provides service to the Internet. And as far as the options here go, let's just make a short list. Number one, we could have wired Ethernet. And that's where the service provider provides effectively a jack here that we can plug into with our RJ45 ended cable and Ethernet cable.

0:31And then on the back end, that would go to their services, which is providing access to the public Internet through a wired Ethernet connection. Another option would be some type of a wireless solution. So for wireless, that could be like 5G, or they could use dedicated frequencies that are allocated to the service provider, or they could use traditional Wi-Fi if they were close enough. So that would be another way that we could interact with our service provider. Another option could be fiber with a fiber-optic connection.

1:01And in that instance, they'd have some jack there that behind the scenes uses fiber to go out to their network. And on the local side, it'd be Ethernet once again with an RJ45 jack you plug into, and away you go. Another option could be using existing phone lines. And originally, when I was first starting in networking, phone lines were being used with modems, and the speed was really, really slow. But now we have technologies like DSL, digital subscriber line, where it's much faster. And of course, the other option that's in many homes would be cable modem, where we have a coax cable that goes out to the service provider, and then we have a box called a cable modem that has an RJ45 jack on it that we then connect into our gear.

1:41And so sometimes a cable modem will have a built-in router in it as well. Also, it may have Wi-Fi services in it as well. It just depends on the vendor and how they set it up. Five common ways of connecting networks to the edge of the Internet through an Internet service provider. So let me show you an example of a cable modem. All right, so here we go. We've got the switch, we've got the router, we've got the firewall, the security appliance, and this is the wireless controller. And here is a cable modem. So it has a coaxial connector here that would connect to the coax network, traditionally used for cable TV, and then we would plug in our gear into this port right here, another RJ45 port, effectively Ethernet connectivity to us, and this makes up the difference between our Ethernet technology and the coax network that the provider is using.

2:30And in addition to basic cable modem services and the vendor who supplies it, it could also include features such as Wi-Fi, additional switch ports, and also Layer 3 routing, again, depending on the vendor and how they're implementing their connectivity to the service provider.

0:00In this video, you and I get to take a big picture look at the end-to-end communications to reinforce the roles that these devices are playing. So let's imagine we have, this is a PC1 and this is PC2 on the same network, and we'll just call this whole thing over here Network A. Put a big A there. And then for clarity, we'll go ahead and call this one Network B. And then over here, off this interface, we'll call this Network C. So every router interface is connected to a different network.

0:32That's how it's routing between the networks using its routing table. So let's start off here with PC1. So PC1 is communicating with PC2. Maybe it's a ping packet or something else like that. So that traffic, as it shows up here at the switch on this port, the switch is going to look at the destination address, the destination layer 2 address, and realize, oh, that's for PC2, which lives off this port. And it does a fast job of doing high-speed layer 2 switching between this incoming port and this outgoing or egress port right here.

1:03And the same thing would happen for the response back. If PC2 replied, it would come in here and the switch would know, oh, the destination layer 2 MAC address of PC1 is off this port and would forward that traffic just out to this port where that PC1 lives. So that's the goal of a switch, to make high-speed switching, aka forwarding decisions inside of a given network. In this case, it's network A. Next, let's move to a router. So let's leave those same networks in place. And let's imagine that we have PC2 now that wants to communicate with this server.

1:35And I'll call the server S3. So the PC is on network A. The server is on network B. So the PC is going to use its default gateway. So that traffic would come into the switch. And the switch at layer 2 would make a forwarding decision out the port where the layer 2 address of this router lives. So the router could receive it. And that's the switch's job, once again, is to forward traffic within a given network. So then the router would receive it. Let's say this is interface 1, interface 2, and interface 3. The router would receive that data and look at its routing table and say, oh, I know how to get to network B.

2:07I need to forward it out this interface 2 right here. At which point the switch would receive that and say, oh, this is destined for this server. And the switch would make a forwarding decision in that same network B to forward it down to the port where the server is. And let's do another example with this device 3 that's going out to server X out here on the public internet. So PC 3 is trying to reach the internet. Literally at layer 2, it's forwarding over to its default gateway. So the switch would receive that here on this port, forward it out the port where the MAC address of the default gateway lives.

2:39And then the router would see that, look at its routing table and say, oh, I need to route this out of the interface 3, which would then be forwarded to the firewall. So the switches are making forwarding decisions inside of a network like network B, and the router is making forwarding decisions between networks, for example, between network A and between network B and between network C. And so for traffic that's going out to the internet, the router would look at its routing table, forward it out interface 3 over to the firewall. And let's imagine the firewall has been configured as a layer 3 device.

3:10Typically they are. And so it also has a routing table. And so it'll make a forwarding decision out to the service provider, but the firewall has the attitude. And the attitude is, is this traffic allowed? Is it the protocols that I'm willing to support? Is it the destination servers I'm willing to forward to, et cetera? And assuming it passes all the rules, then the firewall can forward it. So I think of a firewall, especially a next generation firewall, like a layer 3 router with an attitude because of all the policies surrounding it. And then once it gets to the service provider, to our ISP, it has a similar logic as well. So there's lots and lots and lots of routers on the internet, lots and lots of servers. And they're all going to do that same forwarding game based on their layer 3 routing tables until it's finally delivered to the server.

3:56And if the server responds, that traffic will then go back in the opposite direction. So with layer 2 switches, they are forwarding in the same network based on MAC addresses. A layer 3 router is making forwarding decisions, but it's doing it between networks. And in the world of our current IP networks, instead of calling it network A or network B or network C, we have actual IP network addresses, which we'll discuss in a separate set of videos. But for now, network A, network B, and network C, and routers are routing between those networks based on their routing table. And then for our wireless clients who need to get access to the network, they get access via an access point. And those access points are controlled by a controller.

4:37And that makes it easier for us as administrators to not have to individually manage every single access point. We can just tell the controller what we want to have done, and those access points are then configured by the controller.

0:00At the end of each skill, I like to have some type of a validation exercise or something to help you confirm what you learned and or reinforce it and or identify, hey, I need to revisit those videos again. So for this validation section, here's what I'd like you to do. I'd like you to imagine that a person who is just entering the world of networking has some questions about these devices, including this one, the access point, this one, the switch, this one, the IP telephone, this one, the layer three router, and next generation firewall, as well as a wireless controller. Curious about this acronym P O E. So what I'd like you to do is pause the video right now and then walk through how you would explain these devices, one, two, three, four, five, six, seven devices, and a brief overview for this new person of what they do. And if you feel stuck or like, oh, what does that do again? Feel free to go back to the previous video, review that for a moment and then come back. And one of the tricks that I've learned over the years is that if I go through something with the intent to explain it to somebody and then I walk through that exercise, it's amazing how I can identify, oh, I don't know that quite good enough, or I should review that again. So the benefit of, you know, preparing to teach this to somebody else,

1:19like I'm asking you to do right now, is that you get to confirm and reinforce those concepts in your own mind. So take a moment right now, pause me. And when you're ready, click on resume and we'll walk through this together. All right. So let's start off with the wireless access point. I would say that the wireless access point is like a radio that allows wireless clients like a laptop or a mobile device with a wireless network card to go ahead and logically connect into our network. So it's like the, the gateway from the client over to the physical network for a wireless client. Next, what does a voice over IP telephone do? Voice over IP telephone looks like, feels like a traditional telephone. You pick up the handset, you can speak on it, you can hit the speaker button and talk without the handset.

2:07But behind the scenes, it's digitizing everything that we're saying and then sending that into the network so that voice traffic, which is called voice over IP, because it's carried over an IP network, that voice over IP traffic can be forwarded and routed to wherever it needs to go. And that would normally be between two voice over IP devices, like an IP telephone here, and maybe another IP telephone here, or an IP telephone somewhere else in the network, which leads me to PoE for both of those. So instead of having to supply a transformer and plug it in manually for access points, which may be in awkward positions in the ceiling and so forth, or to have an extra power brick in each office to power the telephones, instead, we can have a switch in the wiring closet that's enabled for PoE, power over Ethernet. And that way, the same Ethernet cable that we're using between those devices and the switch can not only be used for data, which it is, but also be used to deliver power to those devices. So power over Ethernet switch costs a little more than one that doesn't support it. But the savings are incredible when you start taking a look at not having to have individual bricks and not having to have outlets in the ceiling for those bricks in the case of the access points. So for PoE or from the switch,

3:24two devices like IP telephones and access points and IP cameras and so forth, does support that standard. Next, let's talk about the switch. The switch, it does a great job of forwarding traffic in the same network between devices in that network. So here we have device one and device two, they're communicating back and forth. The switch is rapidly forwarding the traffic just between those two ports. And it's not bothering forwarding that traffic between client one and client two out any other ports. Think of it like the switch not bothering people who don't need to see that data, which is good for overall throughput. It's also good for security. Next, let's take a look at routers. Routers are routing between networks. In our case, we had network A over here of this interface, network B over here, and network C. And in its routing table, it knows where those networks are. We can also, in various ways, train a router so it knows how to route to networks that it's not directly connected to. For example, we could have network D out here, and that could also be part of the routing table, or we could use something called a default route.

4:27But behind the scenes, the big picture here with the layer three router is that it is routing or forwarding traffic between two different networks. For example, from network A going over here to network D, based on its routing table, it should know how to forward. Or if it doesn't know how to forward, that's where our traffic stops. But that's the job of a layer three router is to route between different networks. And then as we take a look at a firewall, a next generation firewall, depending on how it's implemented, normally they're implemented as a layer three device. So they kind of look and feel like a router, but they're like a router that has a really bad attitude, meaning I'm looking at everything. I want to analyze everything and make sure nothing goes through that could harm the company or harm the individuals or harm the workstations. And so a next generation firewall could have a lot of different services like intrusion prevention services, or URL filtering, or looking for viruses and malware and so forth.

5:20That classification of a device is generally called a next generation firewall. And again, think of it like a layer three routing device that has an attitude that wants to protect the network. And then last, I don't think we've talked about the controller in this review. So the controller is a great way to manage dozens or hundreds of access points because we can associate the access points with the controller. You and I log onto the controller interface, configure everything there, and then it pushes out the appropriate configs to all the access points. And it can help coordinate access points in working together. And that way you don't have access points that are both trying to override each other on the same frequencies. They can work in harmony inside of our environment. So thanks for joining me in this set of videos in the skill regarding devices on networks and their roles. And if you're interested more about the model approach with the application layer and transport and so forth, that was on the right hand side of the screen. In fact, I think my face is covering some of it right now. Join me in the next skill, and we'll have a deep dive into why that's so important and so relevant for a network engineer today. So I look forward to seeing you in that set of videos soon. Until then, I hope this has been informative and I'd like to thank you for viewing.