WEBVTT 0:00:07.360000 --> 0:00:11.540000 This video, which is part of the Cisco Certified Technician Routing and 0:00:11.540000 --> 0:00:15.980000 Switching Curriculum, is titled Basic Hardware Functionality. 0:00:15.980000 --> 0:00:20.240000 My name is Keith Bogart and I will be your instructor for this session. 0:00:20.240000 --> 0:00:23.760000 In the video overview, we're going to be talking about this bullet point 0:00:23.760000 --> 0:00:26.800000 that you would have seen in the CCT Routing and Switching Blueprint, which 0:00:26.800000 --> 0:00:31.960000 reads, describe in general terms the basic functionality and key differences 0:00:31.960000 --> 0:00:33.900000 for the following hardware. 0:00:33.900000 --> 0:00:38.040000 Land switch, router, modem, and wireless access point. 0:00:38.040000 --> 0:00:42.480000 So, let's go ahead and get into each one of those four things. 0:00:42.480000 --> 0:00:44.480000 Starting with a land switch. 0:00:44.480000 --> 0:00:49.740000 Now, back in the early days of switching, what switches were used for 0:00:49.740000 --> 0:00:54.320000 was very different than what switches are used for in today's networks. 0:00:54.320000 --> 0:00:58.340000 So, back when switches first came out, the primary idea was I had a whole 0:00:58.340000 --> 0:01:02.540000 bunch of equipment that I want to connect to a physical network. 0:01:02.540000 --> 0:01:05.080000 I want to network this equipment together. 0:01:05.080000 --> 0:01:07.740000 I want them all to be in the same broadcast domain. 0:01:07.740000 --> 0:01:11.200000 I want them all as far as layer three was concerned to be in the same 0:01:11.200000 --> 0:01:15.140000 IP network. I just need to connect them together so they could talk. 0:01:15.140000 --> 0:01:18.160000 Hence, I would use a switch to connect them into. 0:01:18.160000 --> 0:01:21.640000 So, each one of those devices would have an Ethernet nit card and the 0:01:21.640000 --> 0:01:26.020000 Ethernet nit card on my laptops and PCs and servers would connect to the 0:01:26.020000 --> 0:01:30.500000 various RJ45 jacks of my Ethernet switch. 0:01:30.500000 --> 0:01:34.200000 And by doing so, they would all be connected to a common network. 0:01:34.200000 --> 0:01:38.240000 Now, I say early days because in the early days, whether you had a switch 0:01:38.240000 --> 0:01:41.620000 like the ones on the right that only had eight ports or you had a monstrous 0:01:41.620000 --> 0:01:45.140000 switch like on the one on the left that had hundreds of ports, all those 0:01:45.140000 --> 0:01:47.920000 ports were in one broadcast domain. 0:01:47.920000 --> 0:01:53.500000 Basically, by connecting your laptops and servers and PCs to these switches, 0:01:53.500000 --> 0:01:57.580000 it was almost as if you were connecting them all to one physical wire. 0:01:57.580000 --> 0:02:02.100000 The laptops PCs and servers didn't know they were connected to a switch. 0:02:02.100000 --> 0:02:05.220000 They just knew that their network interface card was connected to a cable 0:02:05.220000 --> 0:02:09.420000 and that cable was receiving some kind of electrical energy. 0:02:09.420000 --> 0:02:11.580000 So, they knew they were connected to some kind of a network. 0:02:11.580000 --> 0:02:15.100000 They had no idea that they were connected to a hub or a switch or anything 0:02:15.100000 --> 0:02:17.480000 else. They just knew they were connected. 0:02:17.480000 --> 0:02:23.020000 So, once that laptop PC or server put an Ethernet frame onto that cable, 0:02:23.020000 --> 0:02:25.140000 the switch's job was very simple. 0:02:25.140000 --> 0:02:28.360000 As that Ethernet frame came in, the switch would simply take a look at 0:02:28.360000 --> 0:02:30.180000 the destination address in that frame. 0:02:30.180000 --> 0:02:33.960000 Maybe because we're talking about layer two of the OSI model, we're talking 0:02:33.960000 --> 0:02:36.060000 about Ethernet MAC addresses. 0:02:36.060000 --> 0:02:38.640000 The switch would take a look at that layer two destination MAC address 0:02:38.640000 --> 0:02:43.500000 and then just switch that frame out whatever egress port it need to go 0:02:43.500000 --> 0:02:48.560000 on. So, the basic functionality of a switch was basically like this. 0:02:48.560000 --> 0:02:52.300000 Let's just imagine that this is a switch here that has three interfaces 0:02:52.300000 --> 0:02:55.140000 on it, three RJ45 jacks. 0:02:55.140000 --> 0:02:58.720000 And those three RJ45 jacks are connected to a very simple network. 0:02:58.720000 --> 0:03:03.000000 Let's say network that has one server and two laptops on it. 0:03:03.000000 --> 0:03:07.520000 Now, we know that the nicks of each laptop and server has a MAC. 0:03:07.520000 --> 0:03:09.840000 So, let's just say MAC AA. 0:03:09.840000 --> 0:03:12.260000 This one down here will be MAC BB. 0:03:12.260000 --> 0:03:16.540000 And the server's NIC card has a MAC of CC. 0:03:16.540000 --> 0:03:19.080000 Now, we know that in reality, just in case you haven't studied this, the 0:03:19.080000 --> 0:03:23.400000 MAC address is actually, let me ask you, how many bits long? 0:03:23.400000 --> 0:03:26.320000 How many bits is an Ethernet MAC address? 0:03:26.320000 --> 0:03:29.200000 Well, hopefully you answered 48 bits. 0:03:29.200000 --> 0:03:32.900000 That's something you should know for the CCT and moving on forward. 0:03:32.900000 --> 0:03:37.740000 So, a typical MAC address would be represented something like this. 0:03:37.740000 --> 0:03:42.280000 So, it'd be represented as groups of hexadecimal characters. 0:03:42.280000 --> 0:03:46.240000 And with each hexadecimal character, so for example, this is a hexadecimal 0:03:46.240000 --> 0:03:50.720000 character. And when you convert that into binary, each hexadecimal character 0:03:50.720000 --> 0:03:54.040000 is four bits long. 0:03:54.040000 --> 0:03:56.620000 So, that would give me a total of 48 bits. 0:03:56.620000 --> 0:04:02.560000 I'm just making it simple here by saying AA, BB, and CC just for simplification. 0:04:02.560000 --> 0:04:06.980000 Now, in this particular case, the way that a switch worked back then and 0:04:06.980000 --> 0:04:11.380000 still works to this day, as I do this recording, one of the ways is very 0:04:11.380000 --> 0:04:17.460000 similar, which is that when a device transmits any Ethernet frame at all, 0:04:17.460000 --> 0:04:19.880000 we don't even care what's in the body of that frame. 0:04:19.880000 --> 0:04:22.520000 We know that inside that Ethernet frame is going to be the source MAC 0:04:22.520000 --> 0:04:27.640000 address of where that frame came from, which in this case is AA. 0:04:27.640000 --> 0:04:32.460000 Now, a switch has a special table called a MAC address table. 0:04:32.460000 --> 0:04:36.540000 I'll put that right here, MAC address-table. 0:04:36.540000 --> 0:04:39.720000 And so, whenever a frame comes in, it looks at the source MAC address. 0:04:39.720000 --> 0:04:43.880000 If it does not already have that source MAC address in its table, it puts 0:04:43.880000 --> 0:04:49.120000 it in there. Then also says, okay, what interface, what port did this 0:04:49.120000 --> 0:04:50.780000 Ethernet frame come in on? 0:04:50.780000 --> 0:04:55.220000 Let me put some port numbers on here, 01, 02, and 03. 0:04:55.220000 --> 0:05:00.640000 So, in this particular case, we'd say AA was learned on port 0 slash 1. 0:05:00.640000 --> 0:05:05.820000 And as other frames came in, their MAC addresses would also be learned. 0:05:05.820000 --> 0:05:10.600000 And this is how, once the MAC addresses are learned, as we see here, so 0:05:10.600000 --> 0:05:14.220000 now, if this frame up here from AA was actually going to a destination 0:05:14.220000 --> 0:05:19.860000 address of BB, well, now when it came into the switch, the switch would 0:05:19.860000 --> 0:05:24.000000 look in its MAC address table, identify that the destination of BB actually 0:05:24.000000 --> 0:05:30.380000 lives on port 0 slash 2, and it would switch that frame out 0 slash 2. 0:05:30.380000 --> 0:05:33.740000 Now, this is one of the big differences between having everything on a 0:05:33.740000 --> 0:05:36.700000 physical cable, as opposed to a switch. 0:05:36.700000 --> 0:05:40.880000 When Ethernet was very first invented back in the mid-1970s, everything 0:05:40.880000 --> 0:05:45.900000 was tapped into one physical long cable, which meant that even if you 0:05:45.900000 --> 0:05:51.320000 were AA and your destination was BB, everything on that cable saw your 0:05:51.320000 --> 0:05:55.820000 frame. Every NIT card connected to every device on that cable saw your 0:05:55.820000 --> 0:06:00.280000 frame. So, even though BB would see your frame and pick it up, all the 0:06:00.280000 --> 0:06:04.160000 other NIT cards would also see that frame and then discard the frame, 0:06:04.160000 --> 0:06:08.080000 which meant, back in the early days of Ethernet like that, only one person 0:06:08.080000 --> 0:06:09.900000 could talk at a time. 0:06:09.900000 --> 0:06:12.780000 That was it. The rules of Ethernet said, when you're talking, everybody 0:06:12.780000 --> 0:06:13.960000 else has to be listening. 0:06:13.960000 --> 0:06:18.640000 One of the benefits here of having a switch is that's no longer the case. 0:06:18.640000 --> 0:06:23.400000 So, for example, if I put one more device on here, let's just say I put 0:06:23.400000 --> 0:06:30.580000 one more laptop or PC right there, and let's say this PC has a MAC address 0:06:30.580000 --> 0:06:35.960000 of DD. So, now, the beautiful thing about a switch is that a switch has 0:06:35.960000 --> 0:06:40.600000 memory, which means that when an Ethernet frame comes in, it's stored 0:06:40.600000 --> 0:06:45.100000 in memory for a microsecond, looked up, and then sent out. 0:06:45.100000 --> 0:06:48.880000 While while it's being stored in memory, frames can be coming in at exactly 0:06:48.880000 --> 0:06:53.000000 the same time from other interfaces because they're also being stored 0:06:53.000000 --> 0:06:55.940000 in separate locations in memory. 0:06:55.940000 --> 0:06:58.580000 If everything was on one cable, you couldn't do that. 0:06:58.580000 --> 0:07:00.600000 Only one device could talk at a time. 0:07:00.600000 --> 0:07:07.860000 But now, at the exact same time, the AA is trying to send a frame to BB, 0:07:07.860000 --> 0:07:11.540000 DD here. So, we have a source of DD. 0:07:11.540000 --> 0:07:16.440000 So, DD would now be learned on port 0 slash 4. 0:07:16.440000 --> 0:07:18.820000 Let's put that right here. 0:07:18.820000 --> 0:07:22.640000 DD could be sending a frame to destination CC. 0:07:22.640000 --> 0:07:26.500000 That could come in at the exact same time, and then be switched out to 0:07:26.500000 --> 0:07:29.780000 CC. Now, one key point here. 0:07:29.780000 --> 0:07:35.320000 The element or the part of the switch that's doing the switching, that's 0:07:35.320000 --> 0:07:38.680000 looking at the frame as it comes in, looking at the destination MAC address 0:07:38.680000 --> 0:07:40.920000 and saying, okay, where does it go? 0:07:40.920000 --> 0:07:45.280000 The term we'll use for that component is called a forwarding engine. 0:07:45.280000 --> 0:07:49.340000 Now, in this particular case, there's only one forwarding engine in my 0:07:49.340000 --> 0:07:54.740000 entire switch. So, even though these two Ethernet frames came in simultaneously, 0:07:54.740000 --> 0:07:57.600000 they can't both be looked up simultaneously. 0:07:57.600000 --> 0:07:59.020000 That's why we need memory. 0:07:59.020000 --> 0:08:01.500000 So, as they come in, they're both stored in memory. 0:08:01.500000 --> 0:08:04.500000 One of those frames will be sent from memory to the forwarding engine. 0:08:04.500000 --> 0:08:08.700000 It'll be forwarded out, then a picosecond later, the next frame that's 0:08:08.700000 --> 0:08:11.920000 also being stored in memory will be sent to the forwarding engine, and 0:08:11.920000 --> 0:08:15.000000 it will go out. So, this was basic switching. 0:08:15.000000 --> 0:08:19.880000 You want to connect a bunch of devices, laptops, PCs, servers, maybe mainframes, 0:08:19.880000 --> 0:08:21.500000 all onto a network. 0:08:21.500000 --> 0:08:23.240000 You want them all to communicate. 0:08:23.240000 --> 0:08:25.160000 They're all in the same broadcast domain. 0:08:25.160000 --> 0:08:26.600000 What do I mean by broadcast domain? 0:08:26.600000 --> 0:08:30.140000 Well, the way a switch works is if an Ethernet frame comes in and it looks 0:08:30.140000 --> 0:08:34.000000 at the destination MAC address and it says, I have no idea where that 0:08:34.000000 --> 0:08:36.240000 is. That's not a my MAC address table. 0:08:36.240000 --> 0:08:37.540000 I don't know where it is. 0:08:37.540000 --> 0:08:42.020000 One of the behaviors of a switch is the switch will then flood that frame. 0:08:42.020000 --> 0:08:48.280000 For example, if PCDD here sent a frame where the destination MAC address 0:08:48.280000 --> 0:08:54.100000 was a broadcast, like maybe that's trying to do a DHCP or an ARP or something. 0:08:54.100000 --> 0:08:57.940000 Well, a broadcast destination is not going to be in the MAC address table. 0:08:57.940000 --> 0:09:01.560000 So, as that comes in, the switch is going to flood that frame out all 0:09:01.560000 --> 0:09:03.700000 other egress interfaces. 0:09:03.700000 --> 0:09:06.840000 That's why we call it a broadcast domain. 0:09:06.840000 --> 0:09:11.040000 A broadcast domain means when something is flooded, who are all the devices 0:09:11.040000 --> 0:09:15.260000 that see it? Well, in the early days of switching, all the devices connected 0:09:15.260000 --> 0:09:18.280000 the switch, they all saw that flooded traffic. 0:09:18.280000 --> 0:09:20.340000 Hence, that was called a broadcast domain. 0:09:20.340000 --> 0:09:25.620000 Now, let's flash forward to current modern day 2017 as I'm recording this. 0:09:25.620000 --> 0:09:29.220000 Switches these days have lots of additional enhanced capabilities like 0:09:29.220000 --> 0:09:34.920000 VLANs. Primary reason that people buy switches now is because, yes, they 0:09:34.920000 --> 0:09:38.120000 do have a bunch of laptops and PCs and servers that they want to connect 0:09:38.120000 --> 0:09:41.580000 to a network. However, they don't want them all to be in the same broadcast 0:09:41.580000 --> 0:09:45.740000 domain. I have a grouping of equipment over here, which all belongs to 0:09:45.740000 --> 0:09:48.680000 payroll, their laptops, their servers, their PCs. 0:09:48.680000 --> 0:09:53.220000 I've got another subset of equipment over here, which belongs to marketing. 0:09:53.220000 --> 0:09:57.300000 As it so happens, marketing generates a lot of broadcasts. 0:09:57.300000 --> 0:10:00.840000 Just whatever programs and software and applications they happen to use 0:10:00.840000 --> 0:10:04.680000 for their marketing purposes creates a lot of broadcasts. 0:10:04.680000 --> 0:10:07.540000 So, we need the people in marketing and all the people connected to the 0:10:07.540000 --> 0:10:11.460000 switch in that group to see those broadcasts. 0:10:11.460000 --> 0:10:15.420000 However, we don't want those broadcasts interrupting the people in payroll. 0:10:15.420000 --> 0:10:17.600000 They have no need to see those broadcasts. 0:10:17.600000 --> 0:10:20.420000 Even if they did see them, they wouldn't know what to do with them. 0:10:20.420000 --> 0:10:21.840000 That's why we use VLANs. 0:10:21.840000 --> 0:10:25.300000 We still have one physical switch with a whole bunch of ports in it, but 0:10:25.300000 --> 0:10:28.940000 now we tell the switch, hey, this bunch of ports is in a separate group, 0:10:28.940000 --> 0:10:32.140000 a separate VLAN, then this bunch of ports. 0:10:32.140000 --> 0:10:36.520000 So essentially, we've now created two networks, two separate networks, 0:10:36.520000 --> 0:10:40.220000 housed or contained in one physical switch. 0:10:40.220000 --> 0:10:45.380000 So that's the primary sort of way that switches work and why people buy 0:10:45.380000 --> 0:10:51.760000 switches. Now also in today's modern networks, switches can also do routing. 0:10:51.760000 --> 0:10:54.820000 Now, before I talk about routing, let's go on to the slide that actually 0:10:54.820000 --> 0:10:56.280000 talks about routing. 0:10:56.280000 --> 0:10:59.420000 Another common component, routers. 0:10:59.420000 --> 0:11:02.180000 So what makes a router different than a switch? 0:11:02.180000 --> 0:11:05.060000 Well, one thing you'll probably be able to tell if you compare most switches 0:11:05.060000 --> 0:11:09.220000 against routers is that routers don't have nearly as many interfaces or 0:11:09.220000 --> 0:11:11.300000 ports as switches do. 0:11:11.300000 --> 0:11:16.200000 Because switches were designed to connect devices at the access layer. 0:11:16.200000 --> 0:11:20.280000 Basically your servers, your PCs, your hosts, all those devices by your 0:11:20.280000 --> 0:11:24.840000 employees, your IP phones, all those are access layer devices that need 0:11:24.840000 --> 0:11:27.560000 access to the network. 0:11:27.560000 --> 0:11:30.100000 So we have a lot of them and they all need to connect to the network. 0:11:30.100000 --> 0:11:32.780000 So we'll just all plug them into this one box here. 0:11:32.780000 --> 0:11:37.280000 Well, routers, although you can connect a laptop, a PC or a server directly 0:11:37.280000 --> 0:11:42.800000 to a router's interface, that's not normally white people by routers. 0:11:42.800000 --> 0:11:44.780000 So let's go back to my whiteboard again. 0:11:44.780000 --> 0:11:46.560000 So let's build on what we said. 0:11:46.560000 --> 0:11:49.360000 We said we have a bunch of people over here in payroll. 0:11:49.360000 --> 0:11:55.020000 And let's just say that these dots here represent all the laptop servers 0:11:55.020000 --> 0:11:58.200000 and PCs in payroll. 0:11:58.200000 --> 0:12:00.700000 And those things all need network connectivity. 0:12:00.700000 --> 0:12:02.460000 So we'll give them all a cable. 0:12:02.460000 --> 0:12:04.040000 I did a few too many of them. 0:12:04.040000 --> 0:12:04.940000 Let's just delete some of those. 0:12:04.940000 --> 0:12:07.500000 It's going to take me forever to complete this drawing. 0:12:07.500000 --> 0:12:11.720000 And those things are connected to switch ports. 0:12:11.720000 --> 0:12:16.120000 All right, so here's my interfaces on my switch. 0:12:16.120000 --> 0:12:20.000000 Now we also had our good friends in marketing. 0:12:20.000000 --> 0:12:22.800000 So let's put that over here. 0:12:22.800000 --> 0:12:27.380000 Marketing. And we've got, let's just say four devices in marketing, just 0:12:27.380000 --> 0:12:28.840000 to make it simple. 0:12:28.840000 --> 0:12:32.540000 Those four devices also need network connectivity. 0:12:32.540000 --> 0:12:35.560000 So we also connect them to the same switch. 0:12:35.560000 --> 0:12:41.540000 And now to make sure that we keep them separate, we tell the switch, we 0:12:41.540000 --> 0:12:47.560000 say that all of these ports right here are in one VLAN. 0:12:47.560000 --> 0:12:50.820000 Let's just call that VLAN three. 0:12:50.820000 --> 0:12:53.260000 So all these ports are in VLAN three. 0:12:53.260000 --> 0:12:56.260000 And all these ports over here on the left are in some other VLAN. 0:12:56.260000 --> 0:12:59.040000 Let's say VLAN 67. 0:12:59.040000 --> 0:13:02.120000 So by creating these two VLANs and assigning it to these two different 0:13:02.120000 --> 0:13:05.400000 groups of ports, it keeps these devices separate. 0:13:05.400000 --> 0:13:10.500000 Now, that also means if we go up the OSI model to layer three of the OSI 0:13:10.500000 --> 0:13:14.280000 model, layer three is in charge of IP dressing and networking. 0:13:14.280000 --> 0:13:16.720000 We'll talk a little bit more about that in a subsequent video. 0:13:16.720000 --> 0:13:22.660000 But for now, just think of every device connected to a network has a minimum 0:13:22.660000 --> 0:13:24.900000 of two addresses. 0:13:24.900000 --> 0:13:29.600000 On the net card itself, it has a layer two address, which is most likely 0:13:29.600000 --> 0:13:33.140000 a MAC address that we were just talking about, an Ethernet address. 0:13:33.140000 --> 0:13:37.340000 So it can talk to other devices in the same VLAN, in the same broadcast 0:13:37.340000 --> 0:13:41.540000 domain. However, if I want to talk to something that's not in my broadcast 0:13:41.540000 --> 0:13:47.500000 domain, not in my VLAN, now I can't talk to it directly at layer two. 0:13:47.500000 --> 0:13:50.560000 Now I have to say, okay, let's move up the OSI model. 0:13:50.560000 --> 0:13:55.260000 What IP network, what layer three network, MIN. 0:13:55.260000 --> 0:13:59.680000 So for example, payroll, we might say here that in payroll, everybody 0:13:59.680000 --> 0:14:08.580000 in payroll has an address that begins with the number 20 dot something. 0:14:08.580000 --> 0:14:10.980000 So all these laptops here have two addresses. 0:14:10.980000 --> 0:14:14.120000 They have an Ethernet address, a MAC address, which is unique on each 0:14:14.120000 --> 0:14:18.840000 laptop. And they also have a layer three IP address. 0:14:18.840000 --> 0:14:21.700000 Now, in this particular case, all the things here in green have an IP 0:14:21.700000 --> 0:14:23.300000 address that starts the same. 0:14:23.300000 --> 0:14:27.100000 It starts with the number 20, because that's what group they're in. 0:14:27.100000 --> 0:14:29.360000 That's just a number I made up randomly. 0:14:29.360000 --> 0:14:33.060000 And then the remaining bits in their IP address are different. 0:14:33.060000 --> 0:14:37.980000 Similarly, marketing needs to have an IP network assigned to them. 0:14:37.980000 --> 0:14:40.260000 Let's say it's the 30 network. 0:14:40.260000 --> 0:14:46.200000 Okay, so now if payroll needs to talk to payroll, technically we don't 0:14:46.200000 --> 0:14:48.660000 even need IP, although they will be using IP. 0:14:48.660000 --> 0:14:51.060000 But technically to talk to someone in your own group, your own broadcast 0:14:51.060000 --> 0:14:54.500000 domain, all you really need to know is what their MAC address is, and 0:14:54.500000 --> 0:14:56.900000 let them know what your MAC address is. 0:14:56.900000 --> 0:15:01.840000 That's it. But if I'm talking to somebody in a different group, now I 0:15:01.840000 --> 0:15:05.500000 need to know what their IP address is, which means I have to send an IP 0:15:05.500000 --> 0:15:09.960000 packet to them. Well, with original switches, switches originally didn't 0:15:09.960000 --> 0:15:12.680000 have any concept of IP. 0:15:12.680000 --> 0:15:14.660000 All they thought about was MAC addresses. 0:15:14.660000 --> 0:15:17.600000 The only table they maintained was a MAC address table. 0:15:17.600000 --> 0:15:25.880000 And if a frame came in, for example, let's say that this guy right here 0:15:25.880000 --> 0:15:32.240000 in marketing has a MAC address of XXXX. 0:15:32.240000 --> 0:15:38.820000 Now let's say that somehow on my payroll device, let's say this guy right 0:15:38.820000 --> 0:15:42.020000 here, I actually statically do something. 0:15:42.020000 --> 0:15:44.660000 I do something with the DOS command line or something. 0:15:44.660000 --> 0:15:51.780000 So he actually generates a frame, a frame destined to XXXX. 0:15:51.780000 --> 0:15:55.220000 You might think, oh, okay, well then it'll just be switched, right? 0:15:55.220000 --> 0:16:02.320000 No, it won't. Because when that frame comes into this switch, remember 0:16:02.320000 --> 0:16:07.260000 this switch has a MAC address table, the MAC address table is subdivided 0:16:07.260000 --> 0:16:13.280000 by VLAN, MAC, and port. 0:16:13.280000 --> 0:16:17.160000 So in this particular case, when this frame comes in here on the left, 0:16:17.160000 --> 0:16:22.400000 the switch is going to say, oh, okay, that frame came in on VLAN 67. 0:16:22.400000 --> 0:16:30.480000 Do I have any MAC address in VLAN 67 that matches XXXX, where this frame 0:16:30.480000 --> 0:16:33.900000 needs to go? And you'll say, no, I don't. 0:16:33.900000 --> 0:16:36.880000 You might say, but wait a second, he does have MAC address XXXX. 0:16:36.880000 --> 0:16:39.800000 Yes, he does, but it's not in that group. 0:16:39.800000 --> 0:16:42.640000 It's in group VLAN 3. 0:16:42.640000 --> 0:16:46.180000 And the switch is not allowed to say, oh, a frame came in on this group. 0:16:46.180000 --> 0:16:49.620000 Let me see if where that frame needs to go is over here in this other 0:16:49.620000 --> 0:16:53.520000 group. That would completely destroy the whole purpose behind broadcast 0:16:53.520000 --> 0:16:55.160000 domains in the first place. 0:16:55.160000 --> 0:16:59.940000 So the switch cannot take a frame and the data in that frame from one 0:16:59.940000 --> 0:17:04.600000 VLAN, one broadcast domain, and send it to another broadcast domain. 0:17:04.600000 --> 0:17:07.720000 Technically, what's that called is routing. 0:17:07.720000 --> 0:17:09.200000 That's what routing is. 0:17:09.200000 --> 0:17:12.760000 When data from one broadcast domain, in this case, one network, needs 0:17:12.760000 --> 0:17:15.000000 to go to another network. 0:17:15.000000 --> 0:17:18.900000 A switch 20 years ago couldn't do that. 0:17:18.900000 --> 0:17:21.500000 That's where we needed routers. 0:17:21.500000 --> 0:17:25.380000 So here, a router is typically represented as a circle, although we can 0:17:25.380000 --> 0:17:27.860000 see here in this picture, they certainly don't look like that. 0:17:27.860000 --> 0:17:33.320000 But here, we'd have a router and we would have a port on the switch connected 0:17:33.320000 --> 0:17:36.780000 to a router. I'm not going to get into the details of how this works. 0:17:36.780000 --> 0:17:40.900000 If you're interested in this, I advise you to watch the CCNA set of videos. 0:17:40.900000 --> 0:17:45.280000 But here, the router would actually get that frame. 0:17:45.280000 --> 0:17:49.240000 So the frame, well, it couldn't be going to XX. 0:17:49.240000 --> 0:17:51.180000 It just wouldn't work that way. 0:17:51.180000 --> 0:17:55.000000 But basically, what would happen is the router himself has his own MAC 0:17:55.000000 --> 0:17:57.440000 address, this NIC card right here. 0:17:57.440000 --> 0:18:02.680000 Let's just say that that is MAC address ZZ.AA. 0:18:02.680000 --> 0:18:05.900000 So if this person here in payroll said, hey, I need to send some data 0:18:05.900000 --> 0:18:09.720000 to somebody in marketing, he'd say, all right, can't send it to the MAC 0:18:09.720000 --> 0:18:12.000000 address of the person marketing. 0:18:12.000000 --> 0:18:13.340000 That's not allowed. 0:18:13.340000 --> 0:18:17.800000 When I send an ethernet frame at layer two, the destination MAC address 0:18:17.800000 --> 0:18:21.440000 has to be somebody in my group, in my VLAN. 0:18:21.440000 --> 0:18:26.880000 Well, who in my VLAN will know how to get out of my VLAN to another VLAN? 0:18:26.880000 --> 0:18:28.080000 That would be my router. 0:18:28.080000 --> 0:18:32.980000 So this laptop right here, PC server, whatever it happens to be, if he 0:18:32.980000 --> 0:18:40.940000 creates a frame, he says, this data is going to marketing. 0:18:40.940000 --> 0:18:43.580000 He says, OK, who am I marking exactly? 0:18:43.580000 --> 0:18:44.480000 Am I talking to? 0:18:44.480000 --> 0:18:46.460000 Well, we know this guy's going to start with 30. 0:18:46.460000 --> 0:18:49.060000 Let's just say it's 30.111. 0:18:49.060000 --> 0:18:53.220000 This day is going to marketing 30.111. 0:18:53.220000 --> 0:18:58.440000 So at layer three, the networking layer of the OSI model, it says what 0:18:58.440000 --> 0:19:02.620000 the IP address is of the source, this guy in payroll, what the IP address 0:19:02.620000 --> 0:19:07.300000 is of the destination, but at layer two, we have to send the frame to 0:19:07.300000 --> 0:19:10.780000 the router. So the router can actually do the routing for us. 0:19:10.780000 --> 0:19:20.140000 So at layer two, the ethernet destination is going to be zz.aa. 0:19:20.140000 --> 0:19:26.380000 That will ensure, because that is in VLAN 67, that has been learned by 0:19:26.380000 --> 0:19:31.100000 the switch. And we don't know what port that's on. 0:19:31.100000 --> 0:19:34.720000 Let's just say it's on port zero slash six. 0:19:34.720000 --> 0:19:36.700000 That's right here. 0:19:36.700000 --> 0:19:40.540000 That will ensure now that the frame can go down to the router, and then 0:19:40.540000 --> 0:19:44.860000 the router can then route it, can basically send it right back to the 0:19:44.860000 --> 0:19:49.660000 switch again, but now it comes in on VLAN three, it can go across and 0:19:49.660000 --> 0:19:54.040000 up to this guy. So that is the main purpose of routing. 0:19:54.040000 --> 0:19:57.060000 So there's actually several purposes of a router, but the main purpose 0:19:57.060000 --> 0:20:02.100000 of a router is this, to be able to take data from one subnet or one broadcast 0:20:02.100000 --> 0:20:06.820000 domain and route it to a different subnet or a different broadcast domain. 0:20:06.820000 --> 0:20:10.600000 Now the destination he's routing it to in this particular case is actually 0:20:10.600000 --> 0:20:12.000000 directly connected to him. 0:20:12.000000 --> 0:20:16.220000 That router actually knows, hey, I'm connected to VLAN to the 30 network 0:20:16.220000 --> 0:20:18.220000 and to the 20 network. 0:20:18.220000 --> 0:20:21.580000 But sometimes with a router data will come in and the router will say, 0:20:21.580000 --> 0:20:25.660000 well, the destination of where it's going, I don't actually live on that 0:20:25.660000 --> 0:20:28.900000 destination. I don't have a wire or a cable connected to that destination, 0:20:28.900000 --> 0:20:35.620000 but I do know of another router and he's told me he can get to that destination. 0:20:35.620000 --> 0:20:39.360000 So I'll route it to him and then he'll route to somebody else and he'll 0:20:39.360000 --> 0:20:43.220000 route to somebody else until eventually it makes its way to its destination. 0:20:43.220000 --> 0:20:45.880000 So that's the primary purpose of a router. 0:20:45.880000 --> 0:20:48.860000 Now there are a lot of secondary purposes of routers as well. 0:20:48.860000 --> 0:20:52.100000 For example, when we talk about an Ethernet switch, think about that first 0:20:52.100000 --> 0:20:56.180000 word, Ethernet. That means every single interface on that switch is doing 0:20:56.180000 --> 0:20:59.420000 Ethernet. But there's a lot of other protocols as well. 0:20:59.420000 --> 0:21:04.420000 There's PPP, Frame Relay, ATM, ISDN, all kinds of stuff. 0:21:04.420000 --> 0:21:08.160000 Well, what if I have something that comes in that's Ethernet but needs 0:21:08.160000 --> 0:21:12.920000 to go out a Frame Relay or a PPP connection? 0:21:12.920000 --> 0:21:14.320000 Switches don't do that. 0:21:14.320000 --> 0:21:15.960000 That's another use case for a router. 0:21:15.960000 --> 0:21:18.720000 Routers give you the ability to have interfaces that support different 0:21:18.720000 --> 0:21:22.760000 kinds of protocols so you can translate from one to the other. 0:21:22.760000 --> 0:21:27.300000 So those are the two primary reasons why we would have routers in play. 0:21:27.300000 --> 0:21:30.000000 Because we actually want to take data from one network and send it to 0:21:30.000000 --> 0:21:33.560000 another network because we want to translate between different media. 0:21:33.560000 --> 0:21:37.220000 Maybe it's coming in with electrical signaling, has to go out via optical 0:21:37.220000 --> 0:21:39.620000 signaling, all kinds of reasons. 0:21:39.620000 --> 0:21:43.300000 Also routers give us a lot of additional features and protocols available. 0:21:43.300000 --> 0:21:46.560000 There's a lot more security things you can do on a router. 0:21:46.560000 --> 0:21:49.640000 So a lot of good reasons for routers. 0:21:49.640000 --> 0:21:52.400000 All right, what is our next network component? 0:21:52.400000 --> 0:21:55.960000 Modems. Probably you won't see too many of these anymore. 0:21:55.960000 --> 0:21:58.240000 It really depends on what part of the country or what part of the world 0:21:58.240000 --> 0:22:05.080000 you're in. But a modem technically stands for a modulator, demodulator. 0:22:05.080000 --> 0:22:10.120000 Now, nowadays there are things in home networks called cable modems and 0:22:10.120000 --> 0:22:14.740000 DSL modems. And those are doing modulation, demodulation. 0:22:14.740000 --> 0:22:18.960000 But I want to take you back about 20 years and talk about the original 0:22:18.960000 --> 0:22:24.940000 analog modems that modulate and demodulate between analog and digital 0:22:24.940000 --> 0:22:29.300000 signals. So to explain that a little bit, I have to explain to you what's 0:22:29.300000 --> 0:22:32.360000 the difference between an analog and a digital signal. 0:22:32.360000 --> 0:22:37.180000 Okay. Well, as you're listening to this video right now, as you're playing 0:22:37.180000 --> 0:22:39.360000 this, how are you hearing it? 0:22:39.360000 --> 0:22:42.160000 If you really think about it, you've probably got some speakers or something 0:22:42.160000 --> 0:22:43.240000 or maybe some earbuds. 0:22:43.240000 --> 0:22:44.680000 And what's happening? 0:22:44.680000 --> 0:22:49.040000 This video is coming to you from the internet and it's coming to you in 0:22:49.040000 --> 0:22:50.880000 a digital format. 0:22:50.880000 --> 0:22:53.540000 In other words, it's coming to you as electrical pulses. 0:22:53.540000 --> 0:22:55.640000 Some of those pulses represent ones. 0:22:55.640000 --> 0:22:57.880000 Some of those pulses represent zeros. 0:22:57.880000 --> 0:23:02.100000 But as it comes to you in a digital format across your cable modem or 0:23:02.100000 --> 0:23:06.180000 your DSL line or whatever your network is, the electrical signals are 0:23:06.180000 --> 0:23:08.120000 coming in are either one of two things. 0:23:08.120000 --> 0:23:09.520000 It's either a one or a zero. 0:23:09.520000 --> 0:23:14.580000 A whole slew of ones and zeros represents a single pixel in the video. 0:23:14.580000 --> 0:23:17.700000 Another slew of ones and zeros represent another pixel in that video. 0:23:17.700000 --> 0:23:22.040000 So more of those ones and zeros represent one second of audio, right? 0:23:22.040000 --> 0:23:24.880000 But it's all digital coming down to you. 0:23:24.880000 --> 0:23:27.980000 But clearly your ears can't hear in digital. 0:23:27.980000 --> 0:23:30.400000 They can't hear in electrical signals. 0:23:30.400000 --> 0:23:32.100000 So what's happening in your computer? 0:23:32.100000 --> 0:23:36.660000 Well, all that digital signaling eventually makes its way to your speakers. 0:23:36.660000 --> 0:23:38.820000 Actually, it's a little bit more complicated than that, but let's just 0:23:38.820000 --> 0:23:39.840000 leave it with this. 0:23:39.840000 --> 0:23:43.580000 And what your speakers do, they modulate and demodulate. 0:23:43.580000 --> 0:23:45.820000 Basically, what they're doing is they're taking those digital signals 0:23:45.820000 --> 0:23:52.120000 that electric, that electricity and converting it, it's pushing the speakers. 0:23:52.120000 --> 0:23:54.880000 So the speakers are actually pushing air, right? 0:23:54.880000 --> 0:23:58.140000 And if you actually looked at it, now speakers don't just push air one 0:23:58.140000 --> 0:23:59.700000 way and then a little way, right? 0:23:59.700000 --> 0:24:03.020000 If you were actually to take a look over time as the speaker is pushing 0:24:03.020000 --> 0:24:05.380000 out the air, which is a thump, right? 0:24:05.380000 --> 0:24:07.760000 That's, and that's how your ear interprets it. 0:24:07.760000 --> 0:24:10.540000 If you actually look at that over time, if you slowed that down over one 0:24:10.540000 --> 0:24:14.600000 second, you have the air pulse pushing, pushing, pushing, pushing, pushing, 0:24:14.600000 --> 0:24:17.180000 retracting, retracting, retracting, retracting, and attracting, pushing, 0:24:17.180000 --> 0:24:18.980000 pushing, retracted. 0:24:18.980000 --> 0:24:20.720000 That's what your speaker is looking at. 0:24:20.720000 --> 0:24:23.000000 If you remember, we looked at speaker in slow motion, even though it's 0:24:23.000000 --> 0:24:25.480000 going like this, and we can barely see it with our eyes in slow motion, 0:24:25.480000 --> 0:24:28.560000 it's pushing out, coming back, pushing out, coming back, because there's 0:24:28.560000 --> 0:24:30.800000 a magnet behind that speaker. 0:24:30.800000 --> 0:24:34.140000 And as the electrical signals are hitting that magnet, it's causing the 0:24:34.140000 --> 0:24:38.600000 magnet to generate electrical fields, which are pushing out the speaker 0:24:38.600000 --> 0:24:41.560000 and then retracting it, pushing out the speaker and retracting it. 0:24:41.560000 --> 0:24:46.300000 So really, the air that's coming to your ear, which is causing your eardrums 0:24:46.300000 --> 0:24:50.800000 to vibrate so you can hear me, that is an analog signal. 0:24:50.800000 --> 0:24:54.300000 It's not just one thing or another thing that air is coming to stronger, 0:24:54.300000 --> 0:24:56.560000 stronger, stronger week, week, week, week, week, week, stronger, stronger, 0:24:56.560000 --> 0:24:59.500000 stronger, week, week, week, week, week, and depending on how often that 0:24:59.500000 --> 0:25:03.800000 happens, depends on what, if I'm talking, hi, Revan Doggino, that's the 0:25:03.800000 --> 0:25:08.280000 frequency, but that is an analog waveform, something that goes like this 0:25:08.280000 --> 0:25:14.220000 over time that's continuous as an infinite amount of things it could represent. 0:25:14.220000 --> 0:25:18.400000 You know, in this analog waveform, there's an infinite amount of possibilities 0:25:18.400000 --> 0:25:22.320000 of what any particular point on that line could possibly be. 0:25:22.320000 --> 0:25:27.600000 So analog means it's infinite, it's smooth, and continuous over time, 0:25:27.600000 --> 0:25:33.500000 whereas digital means it's just a pulse that's either one of two values, 0:25:33.500000 --> 0:25:36.680000 a one or zero, that's what we mean by digital. 0:25:36.680000 --> 0:25:39.000000 So what does that have to do with modems? 0:25:39.000000 --> 0:25:42.660000 So with a modem, it was just the opposite of what I just described. 0:25:42.660000 --> 0:25:48.160000 So with a modem, you were on your laptop and you were typing something 0:25:48.160000 --> 0:25:51.720000 away that's all digital, it's all electrical in your laptop, it's creating 0:25:51.720000 --> 0:25:55.880000 ones and zeros, and then when it got to the modem, so that's what we have 0:25:55.880000 --> 0:25:59.860000 here. So if we take a look at this, actually let me bring something up 0:25:59.860000 --> 0:26:02.580000 real quick so I can draw on here. 0:26:02.580000 --> 0:26:10.040000 Great. So, okay, so from here, from the laptop to the modem, you have 0:26:10.040000 --> 0:26:16.740000 digital signals, ones and zeros coming out, that's all electricity. 0:26:16.740000 --> 0:26:20.920000 But this modem was designed to operate across the local loop, which was 0:26:20.920000 --> 0:26:23.960000 your telephone line, your telephone wire going into your house, it's been, 0:26:23.960000 --> 0:26:26.340000 you know, there since like the 1800s. 0:26:26.340000 --> 0:26:31.100000 That was designed to carry waveforms, to carry analog signals, so your 0:26:31.100000 --> 0:26:37.700000 modem changed it from digital to analog, and so what ended up coming and 0:26:37.700000 --> 0:26:42.840000 looked like this now is looking like a waveform over time. 0:26:42.840000 --> 0:26:48.880000 So we were modulating and demodulating the signal from analog to digital, 0:26:48.880000 --> 0:26:53.200000 and then all the way back here again, here at the far end is our analog 0:26:53.200000 --> 0:26:57.160000 signal coming in, when it gets to the modem, it comes out on the other 0:26:57.160000 --> 0:27:01.860000 side as a digital signal, ones and zeros. 0:27:01.860000 --> 0:27:07.540000 So that's what a modem did, and essentially when we talk about cable modems 0:27:07.540000 --> 0:27:13.000000 or DSL modems, they are still modulating and demodulating stuff, they're 0:27:13.000000 --> 0:27:18.260000 still taking what is sort of like an analog frequency and modulating that 0:27:18.260000 --> 0:27:21.440000 into digital, now it's a lot more complicated than that, but that's basically 0:27:21.440000 --> 0:27:25.060000 what a modem is, it's something that's sort of converting modulating, 0:27:25.060000 --> 0:27:30.720000 demodulating from a digital to an analog signal, and this is what modems 0:27:30.720000 --> 0:27:33.140000 look like way back in the day. 0:27:33.140000 --> 0:27:38.000000 And the last thing I want to talk about is a Wi-Fi access point. 0:27:38.000000 --> 0:27:42.380000 Now up until now, everything that we've been looking at switches, routers 0:27:42.380000 --> 0:27:48.300000 and modems, carried your information either via an electrical signal, 0:27:48.300000 --> 0:27:52.660000 which was done most of the time, or an optical signal. 0:27:52.660000 --> 0:27:56.660000 So for example, there are fiber optic cables that are made out very thin 0:27:56.660000 --> 0:28:02.360000 strands of glass, and those fiber optic signals carry your ones and zeros, 0:28:02.360000 --> 0:28:06.420000 but as light pulses, as like laser light, and that's why fiber optics 0:28:06.420000 --> 0:28:15.460000 are so much faster than electrical cables, because but now we have a third 0:28:15.460000 --> 0:28:18.460000 kind of medium, radio frequencies. 0:28:18.460000 --> 0:28:20.920000 So just like your car, think about your car, how's it, you know, when 0:28:20.920000 --> 0:28:23.640000 you're in your car and you're listening to your car radio, what's really 0:28:23.640000 --> 0:28:27.600000 going on? Well, all throughout the air, penetrating your body and your 0:28:27.600000 --> 0:28:34.720000 brain and everything else are hundreds, if not more, radio frequency signals. 0:28:34.720000 --> 0:28:37.600000 I mean, if you think about how many radio stations do you think you can 0:28:37.600000 --> 0:28:40.600000 tune in right now on your radio? 0:28:40.600000 --> 0:28:46.100000 Probably at least because you're tuned in to one of those channels right 0:28:46.100000 --> 0:28:47.340000 now and you're listening to it. 0:28:47.340000 --> 0:28:50.360000 Does that mean the other channels aren't transmitting? 0:28:50.360000 --> 0:28:52.280000 No, they're transmitting. 0:28:52.280000 --> 0:28:54.900000 It's just that your radio is not listening to them. 0:28:54.900000 --> 0:28:57.280000 It's sort of like a whole bunch of people talking at the same time in 0:28:57.280000 --> 0:29:01.140000 a room, but you have the capability of ignoring everybody and just focusing 0:29:01.140000 --> 0:29:03.220000 in on your friend Bob over there. 0:29:03.220000 --> 0:29:06.760000 As Bob's talking, you can pay attention to him and you can sort of zone 0:29:06.760000 --> 0:29:10.280000 out everybody else, even though everybody's talking at the same time. 0:29:10.280000 --> 0:29:11.500000 Well, that's how radio works. 0:29:11.500000 --> 0:29:16.480000 You got all these at exactly the same time, but the radio in your car 0:29:16.480000 --> 0:29:19.580000 has a capability of tuning in to just one. 0:29:19.580000 --> 0:29:22.240000 That's like what a Wi -Fi access point does. 0:29:22.240000 --> 0:29:27.960000 It uses radio frequencies to both transmit and receive. 0:29:27.960000 --> 0:29:31.280000 So whereas the radio in your car is only capable of receiving, it's just 0:29:31.280000 --> 0:29:36.300000 a receiver, a Wi-Fi access point has both a receiver and a transmitter 0:29:36.300000 --> 0:29:41.340000 in it. So not only can it transmit radio frequency to your laptop, your 0:29:41.340000 --> 0:29:44.360000 laptop has some antennas in it. 0:29:44.360000 --> 0:29:47.320000 You might be surprised because you might say, hey, I'm looking at my laptop. 0:29:47.320000 --> 0:29:50.520000 I'm looking at my phone right now, my tablet. 0:29:50.520000 --> 0:29:52.380000 I don't see any antennas. 0:29:52.380000 --> 0:29:55.260000 There are actually antennas that are usually built into the casing or 0:29:55.260000 --> 0:29:55.920000 built into the housing. 0:29:55.920000 --> 0:30:01.180000 Like for example, most laptops, the screen actually contains one or more 0:30:01.180000 --> 0:30:02.920000 antennas in the screen itself. 0:30:02.920000 --> 0:30:07.060000 If you have a laptop that's capable of Wi-Fi, you absolutely have some 0:30:07.060000 --> 0:30:10.000000 antennas in there, just like the antenna in your car. 0:30:10.000000 --> 0:30:14.360000 And those antennas are capable of receiving radio frequencies, which it 0:30:14.360000 --> 0:30:19.360000 can then convert into electrical energy, which are your ones and zeros 0:30:19.360000 --> 0:30:23.040000 electrically. So you got radio frequency coming in, and then within your 0:30:23.040000 --> 0:30:27.860000 Wi-Fi, NIC card is converting that into ones and zeros as electrical energy, 0:30:27.860000 --> 0:30:29.500000 which then goes to your processor. 0:30:29.500000 --> 0:30:33.840000 Similarly, in your laptop, you also have a transmitter. 0:30:33.840000 --> 0:30:36.560000 This is something your radio in your car doesn't have. 0:30:36.560000 --> 0:30:38.020000 It's just a receiver. 0:30:38.020000 --> 0:30:42.320000 But your laptop, your smartphone, your tablet is capable of receiving 0:30:42.320000 --> 0:30:44.700000 and transmitting. 0:30:44.700000 --> 0:30:47.000000 We actually call that a transceiver. 0:30:47.000000 --> 0:30:51.120000 A transceiver is a combination of a transmitter and a receiver. 0:30:51.120000 --> 0:30:54.600000 So anything that's capable of Wi-Fi has a transceiver in it. 0:30:54.600000 --> 0:30:58.660000 It's got something capable of taking electrical energy that you create, 0:30:58.660000 --> 0:31:02.580000 like your web page or your email, sending it to your antennas, which then 0:31:02.580000 --> 0:31:04.500000 radiate it out as radio frequency. 0:31:04.500000 --> 0:31:09.340000 So you're transmitting, and then the antennas on the Wi-Fi access point 0:31:09.340000 --> 0:31:13.440000 take that radio frequency in, convert it into electrical energy, and on 0:31:13.440000 --> 0:31:17.080000 the back end, that access point has an ethernet cable in it. 0:31:17.080000 --> 0:31:20.720000 So then sends that electrical energy to a switch. 0:31:20.720000 --> 0:31:26.160000 So an access point is sort of like a router in that it's translating between 0:31:26.160000 --> 0:31:28.940000 different types of media. 0:31:28.940000 --> 0:31:35.860000 The antenna are using radio frequencies to send and receive, and the ethernet 0:31:35.860000 --> 0:31:39.000000 port, which we don't really see here, but every single Wi-Fi access point 0:31:39.000000 --> 0:31:43.920000 has one, is using electrical cabling and electrical copper cabling to 0:31:43.920000 --> 0:31:46.780000 transmit and receive its data. 0:31:46.780000 --> 0:31:52.520000 So we've got RF in and electrical out, or electrical in, and RF out radio 0:31:52.520000 --> 0:31:56.000000 frequency. So that's what a Wi-Fi access point is. 0:31:56.000000 --> 0:32:00.280000 A Wi-Fi access point is a device typically sits in the ceiling or maybe 0:32:00.280000 --> 0:32:05.100000 on a desk somewhere, and a whole bunch of devices that have antennas like 0:32:05.100000 --> 0:32:09.300000 your laptop, your smartphone, your tablet, which are capable of Wi-Fi, 0:32:09.300000 --> 0:32:12.620000 can all talk to that Wi-Fi access point. 0:32:12.620000 --> 0:32:14.700000 Now, it's sort of like they're talking to a switch. 0:32:14.700000 --> 0:32:18.140000 With Wi-Fi, only one person can talk at a time. 0:32:18.140000 --> 0:32:19.980000 Only one person can transmit at a time. 0:32:19.980000 --> 0:32:23.880000 Now, there's all sorts of complex mechanisms to make sure that only one 0:32:23.880000 --> 0:32:27.220000 person's talking at a time, and it doesn't always work that way, which 0:32:27.220000 --> 0:32:30.180000 causes some problems, but that's the way Wi-Fi works. 0:32:30.180000 --> 0:32:35.040000 I could have 20 devices all sitting around this one Wi-Fi access point 0:32:35.040000 --> 0:32:36.700000 that's like here in the ceiling. 0:32:36.700000 --> 0:32:40.100000 One person can talk, and then the Wi -Fi will take that and then convert 0:32:40.100000 --> 0:32:43.440000 it into an ethernet frame and send it across ethernet cable, and then 0:32:43.440000 --> 0:32:45.880000 the next person can talk, and then the same thing. 0:32:45.880000 --> 0:32:55.060000 When stuff is coming down from the wired network, like something from 0:32:55.060000 --> 0:32:58.540000 the Wi-Fi access point, which then listens to see, make sure that the 0:32:58.540000 --> 0:33:02.260000 airspace is free, that nobody's transmitting right now, if the airspace 0:33:02.260000 --> 0:33:06.380000 is free, takes out ethernet frame, and then converts it into radio frequency 0:33:06.380000 --> 0:33:09.780000 energy and sends it out into the airspace. 0:33:09.780000 --> 0:33:14.460000 Everybody hears it, but only the Wi -Fi nit cards actually meant for will 0:33:14.460000 --> 0:33:16.120000 pay attention to it. 0:33:16.120000 --> 0:33:20.880000 So that is how Wi-Fi access point works, and that concludes this video.