WEBVTT 0:00:07.200000 --> 0:00:11.840000 This video, which is part of the CCT routing and switching set, is titled 0:00:11.840000 --> 0:00:15.080000 What is an IP address and subnet. 0:00:15.080000 --> 0:00:19.500000 My name is Keith Bogart and I will be your instructor for this video. 0:00:19.500000 --> 0:00:22.100000 So let's talk about the objectives for this particular video. 0:00:22.100000 --> 0:00:26.640000 In the CCT routing and switching blueprint in section 3, it says that 0:00:26.640000 --> 0:00:31.320000 you need to be able to describe what an IP address and subnet is. 0:00:31.320000 --> 0:00:33.660000 It should be what an IP address and subnet are. 0:00:33.660000 --> 0:00:35.580000 But that is what the blueprint says. 0:00:35.580000 --> 0:00:38.220000 So let's talk a little bit about this. 0:00:38.220000 --> 0:00:41.900000 So in order to describe this, I'm going to do pretty much the entire thing 0:00:41.900000 --> 0:00:44.320000 using the whiteboard right here. 0:00:44.320000 --> 0:00:50.180000 So in the previous video I did talking about the different components 0:00:50.180000 --> 0:00:54.000000 of a network where I described the basics of a switch and the basics of 0:00:54.000000 --> 0:00:58.120000 a router. I introduced you to the concept that every device connected 0:00:58.120000 --> 0:01:02.380000 via Ethernet has an Ethernet address called a MAC address. 0:01:02.380000 --> 0:01:03.640000 And that's where I've drawn right here. 0:01:03.640000 --> 0:01:07.540000 MAC address is 11, 22, 33, and so forth. 0:01:07.540000 --> 0:01:11.700000 And I said by having that MAC address, a device is able to send an Ethernet 0:01:11.700000 --> 0:01:18.720000 frame to another device in its VLAN, in its network, and address that 0:01:18.720000 --> 0:01:23.580000 frame to the destination MAC address of who he wants to talk to. 0:01:23.580000 --> 0:01:28.780000 So for example, if Bob wants to send some data to Sue, then that particular 0:01:28.780000 --> 0:01:34.040000 case, Bob's data is going to come into the switch and the destination 0:01:34.040000 --> 0:01:38.580000 MAC address of that data, if it's going to Sue, is going to be 33. 0:01:38.580000 --> 0:01:43.720000 Now it's beyond the scope of this class to explain how did Bob learn that? 0:01:43.720000 --> 0:01:46.800000 How did Bob learn that the destination MAC address should be 33? 0:01:46.800000 --> 0:01:51.740000 Watch the CCNA series and look for this specific section called ARP, Address 0:01:51.740000 --> 0:01:54.460000 Resolution Protocol, to explain that. 0:01:54.460000 --> 0:01:57.900000 However, we're just going to assume that Bob knew that 33 is Sue when 0:01:57.900000 --> 0:02:01.160000 that comes in. We also learned from the last video that the switch has 0:02:01.160000 --> 0:02:03.780000 something called a MAC address table. 0:02:03.780000 --> 0:02:07.840000 In that MAC address table, the switch will look up and it'll say, oh, 0:02:07.840000 --> 0:02:12.940000 okay, a frame just came in from this group of devices that's in payroll. 0:02:12.940000 --> 0:02:16.440000 And how does the switch know that these four devices on top should all 0:02:16.440000 --> 0:02:21.560000 be part of the same layer two group based on another concept we talked 0:02:21.560000 --> 0:02:24.480000 about, which is called a VLAN or a virtual LAN. 0:02:24.480000 --> 0:02:29.280000 So in this particular case, I would have to decide for myself what VLAN 0:02:29.280000 --> 0:02:33.300000 number, just as an identifier, but what VLAN number do I want to assign 0:02:33.300000 --> 0:02:36.760000 to all the devices connected to payroll? 0:02:36.760000 --> 0:02:40.060000 So what if I just said, all right, well, I got a pretty large range there 0:02:40.060000 --> 0:02:44.080000 I can choose from, let's just do VLAN 11. 0:02:44.080000 --> 0:02:49.320000 So all these ports connected to devices in payroll are in VLAN 11 and 0:02:49.320000 --> 0:02:51.980000 that's what V.11 stands for here. 0:02:51.980000 --> 0:02:56.160000 So when this Ethernet frame came in from Bob, the switch would say, okay, 0:02:56.160000 --> 0:02:59.740000 number one, it came in a port that's in VLAN 11. 0:02:59.740000 --> 0:03:03.960000 Number two, do I already have the source MAC address of 11? 0:03:03.960000 --> 0:03:08.280000 If I don't learn it, put it in my MAC address table, say, 11 lives in 0:03:08.280000 --> 0:03:11.200000 VLAN 11, it lives on port number one. 0:03:11.200000 --> 0:03:14.720000 If it's already in my MAC address table, great. 0:03:14.720000 --> 0:03:16.960000 Now look at the destination MAC address. 0:03:16.960000 --> 0:03:20.120000 Ah, the destination MAC address is 3-3. 0:03:20.120000 --> 0:03:22.220000 Go back to my MAC address table. 0:03:22.220000 --> 0:03:27.520000 Do I have MAC address 3-3 also residing in VLAN 11? 0:03:27.520000 --> 0:03:30.400000 On this particular case, you'd say, yes, I do. 0:03:30.400000 --> 0:03:33.460000 And you would take that frame and the switch would then switch it out 0:03:33.460000 --> 0:03:36.440000 this interface right here. 0:03:36.440000 --> 0:03:39.960000 And similarly, if Kevin and Kurt were talking to each other, the exact 0:03:39.960000 --> 0:03:41.900000 same process would happen. 0:03:41.900000 --> 0:03:44.940000 The only difference is the VLAN would be different because these guys 0:03:44.940000 --> 0:03:48.540000 are all in marketing and marketing has a different VLAN identifier. 0:03:48.540000 --> 0:03:51.860000 Let's say they are VLAN 24. 0:03:51.860000 --> 0:03:55.900000 So everything in blue is VLAN 24. 0:03:55.900000 --> 0:04:00.260000 Now this is the extent of the limitations of a basic switch. 0:04:00.260000 --> 0:04:03.560000 When Ethernet frame comes in, the switch says, look, I can switch that 0:04:03.560000 --> 0:04:08.220000 frame as long as the frame is in the exact same group, the exact same 0:04:08.220000 --> 0:04:11.840000 VLAN as the source where the frame came in. 0:04:11.840000 --> 0:04:14.980000 And then we talked about in the last video, we said, well, what if a device 0:04:14.980000 --> 0:04:19.620000 in one group, for example, what if Kevin wanted to send data to the server 0:04:19.620000 --> 0:04:23.740000 in payroll? What if Kevin says, hey, I was supposed to get a raise last 0:04:23.740000 --> 0:04:26.380000 week and I wonder if it's taken effect yet. 0:04:26.380000 --> 0:04:30.200000 I'm all logging into the payroll server, find my record there, and see 0:04:30.200000 --> 0:04:33.300000 if my raise has actually been implemented. 0:04:33.300000 --> 0:04:36.740000 Well, in that particular case, now Kevin's going to be sending some data, 0:04:36.740000 --> 0:04:41.840000 it's going to be coming in VLAN 24, and the switch by itself is not going 0:04:41.840000 --> 0:04:46.440000 to be able to take that data and send it out a port in VLAN 11. 0:04:46.440000 --> 0:04:48.860000 That's where we would need a router. 0:04:48.860000 --> 0:04:52.800000 Now let's bring it back to Kevin's perspective for a moment. 0:04:52.800000 --> 0:04:58.760000 Now as of this drawing here, the only identifier, the only numerical identifier 0:04:58.760000 --> 0:05:05.340000 that Kevin and the identifier, the identifier that identifies them as 0:05:05.340000 --> 0:05:12.000000 a unique entity in their VLAN on their cable, 77, 66, 55, so on and so 0:05:12.000000 --> 0:05:16.440000 forth. But that can't be used if you want to send data to a different 0:05:16.440000 --> 0:05:22.420000 network. So in addition to having a layer 2 address, a MAC address, every 0:05:22.420000 --> 0:05:27.280000 single device also has to know, okay, what network am I in? 0:05:27.280000 --> 0:05:29.120000 I am in a common network. 0:05:29.120000 --> 0:05:33.400000 There's a bunch of other devices probably in the same network as me, and 0:05:33.400000 --> 0:05:37.700000 I need to have an address that's unique to this network. 0:05:37.700000 --> 0:05:38.920000 So how do we do this? 0:05:38.920000 --> 0:05:41.560000 This is where IP comes into play. 0:05:41.560000 --> 0:05:46.300000 So in my particular case, I've just labeled my networks as their functional 0:05:46.300000 --> 0:05:48.780000 name, like payroll, marketing. 0:05:48.780000 --> 0:05:51.380000 But remember, in the world of networking, everything's done via binary 0:05:51.380000 --> 0:05:53.920000 and via numbers. 0:05:53.920000 --> 0:05:58.580000 So the designers of IP said every single network, regardless of whether 0:05:58.580000 --> 0:06:02.260000 it's got two devices in it or 200 devices in it, no matter how big or 0:06:02.260000 --> 0:06:06.040000 small it is, has to be represented by a number. 0:06:06.040000 --> 0:06:10.120000 So every single device in this network is going to have a certain number 0:06:10.120000 --> 0:06:12.860000 that says, oh, we are in a common network. 0:06:12.860000 --> 0:06:19.500000 Now the designers of IP said an IP address is going to be, let me bring 0:06:19.500000 --> 0:06:24.060000 this up here. 32 bits long. 0:06:24.060000 --> 0:06:28.200000 32 bits long. So find to go back to my whiteboard here for a moment. 0:06:28.200000 --> 0:06:33.560000 32 bits. One, two, three, four, five, six, seven, eight. 0:06:33.560000 --> 0:06:38.780000 One, two, three, four, five, six, seven, eight. 0:06:38.780000 --> 0:06:43.320000 One, two, three, four, five, six, seven, eight. 0:06:43.320000 --> 0:06:47.460000 OneForeign. Two, three, four, five, six, seven, eight. 0:06:47.460000 --> 0:06:50.660000 Okay, so there is 32 bits. 0:06:50.660000 --> 0:06:54.120000 Now basically this is 32 placeholders where I could put bits. 0:06:54.120000 --> 0:06:56.720000 But we know that bit is either going to be a one or a zero. 0:06:56.720000 --> 0:06:58.760000 That's all a bit could be, a one or a zero. 0:06:58.760000 --> 0:07:02.700000 So there's going to be some combination of ones and zeros right here. 0:07:02.700000 --> 0:07:10.900000 I'm not going to fill out the whole thing, but so when you put an IP address 0:07:10.900000 --> 0:07:16.240000 on a laptop or on a computer or a smartphone or a tablet or whatever it 0:07:16.240000 --> 0:07:23.040000 is, it's going to be given a 32 bit address in binary that looks something 0:07:23.040000 --> 0:07:27.000000 like this, some combination of ones and zeros. 0:07:27.000000 --> 0:07:33.960000 Now the next thing about the IP address is that something about this IP 0:07:33.960000 --> 0:07:46.560000 address, some just doing this arbitrarily, represents the network. 0:07:46.560000 --> 0:07:51.700000 In other words, if I say, all right, well everybody in payroll needs to 0:07:51.700000 --> 0:07:55.820000 be on an IP network, which means they all need to have an IP address, 0:07:55.820000 --> 0:08:01.020000 which means they all have a 32 bit address and some portion of the first 0:08:01.020000 --> 0:08:05.480000 set of bits is common among everybody in payroll. 0:08:05.480000 --> 0:08:09.200000 So for example, I might say, all right, well everybody in payroll is going 0:08:09.200000 --> 0:08:11.120000 to have this pattern. 0:08:11.120000 --> 0:08:15.140000 The first eight bits is going to be one zero one zero one zero one zero 0:08:15.140000 --> 0:08:19.140000 one zero. I'm not going to add that up, but whatever number that is, that's 0:08:19.140000 --> 0:08:21.540000 common to payroll. 0:08:21.540000 --> 0:08:27.460000 So which means this portion of the IP address is called the network portion 0:08:27.460000 --> 0:08:30.520000 or the network ID. 0:08:30.520000 --> 0:08:34.300000 In this case, the network ID is one zero one zero one zero one zero one 0:08:34.300000 --> 0:08:36.620000 zero. That's what everybody in payroll has. 0:08:36.620000 --> 0:08:42.880000 And this remaining portion of the IP address, all of these bits in this 0:08:42.880000 --> 0:08:52.060000 particular case is called the host bits, which means let's say for example 0:08:52.060000 --> 0:08:55.440000 that we had 25 people in payroll. 0:08:55.440000 --> 0:08:59.320000 We know that all those devices when they connect to a switch are all going 0:08:59.320000 --> 0:09:00.480000 to be in the same VLAN. 0:09:00.480000 --> 0:09:03.880000 We don't know what that VLAN is, but whatever it is, it's going to be 0:09:03.880000 --> 0:09:08.020000 the same for all 25 devices because they're all in the same group. 0:09:08.020000 --> 0:09:09.200000 They're all in payroll. 0:09:09.200000 --> 0:09:13.620000 Now at layer three, all 25 devices are going to have a 32-bit address 0:09:13.620000 --> 0:09:15.140000 called an IP address. 0:09:15.140000 --> 0:09:20.400000 Of all of their IP addresses, the first eight bits in this example are 0:09:20.400000 --> 0:09:21.460000 going to be the same. 0:09:21.460000 --> 0:09:25.320000 John, Sally, Sue, Bob, Kelly, whatever, all those payroll people will 0:09:25.320000 --> 0:09:28.460000 have an IP address beginning with one zero one zero one zero one zero. 0:09:28.460000 --> 0:09:31.600000 The rest of the bits will be different. 0:09:31.600000 --> 0:09:37.140000 So for example, this pattern of bits right here might be what Bob gets. 0:09:37.140000 --> 0:09:40.020000 A different pattern of bits. 0:09:40.020000 --> 0:09:42.680000 So Sally, she's also in payroll, right? 0:09:42.680000 --> 0:09:45.680000 Well Sally's going to get one zero one zero one zero one zero. 0:09:45.680000 --> 0:09:51.280000 She's in the same group, but her remaining bits might look like this. 0:09:51.280000 --> 0:09:57.760000 That's a different pattern because she is a different host. 0:09:57.760000 --> 0:10:02.700000 So every device in this network, whether it be a printer, a fax machine, 0:10:02.700000 --> 0:10:06.760000 a laptop, or a server, is considered a host in the network. 0:10:06.760000 --> 0:10:11.580000 As such, every single one of those devices needs to have two addresses, 0:10:11.580000 --> 0:10:15.580000 a layer two MAC address, so it can talk to other hosts in the exact same 0:10:15.580000 --> 0:10:19.200000 VLAN. It also needs to have a layer three IP address. 0:10:19.200000 --> 0:10:23.280000 And now we know that layer three IP address is going to be 32 bits long. 0:10:23.280000 --> 0:10:28.300000 Some portion of it is going to be common among all the other devices in 0:10:28.300000 --> 0:10:29.760000 that same group. 0:10:29.760000 --> 0:10:31.620000 That will be the network portion. 0:10:31.620000 --> 0:10:35.600000 The remaining portion is going to be unique for every single device. 0:10:35.600000 --> 0:10:38.940000 Every single device will have unique host bits. 0:10:38.940000 --> 0:10:42.420000 And so this comprises our IP address. 0:10:42.420000 --> 0:10:45.780000 Now you might be wondering, well, okay, so Keith, you're telling me that 0:10:45.780000 --> 0:10:49.420000 my laptop has a MAC address and IP address. 0:10:49.420000 --> 0:10:54.020000 And you told me that my IP address is 32 bits long and somewhere in the 0:10:54.020000 --> 0:10:58.860000 first part of that IP address is the network portion. 0:10:58.860000 --> 0:11:00.700000 Is it the first eight bits? 0:11:00.700000 --> 0:11:04.580000 I don't know. It could be a variety that could be the first eight bits. 0:11:04.580000 --> 0:11:07.840000 It could be the first 16 bits, the first 29 bits. 0:11:07.840000 --> 0:11:11.040000 That might leave you scratching your head saying, well, wait a second. 0:11:11.040000 --> 0:11:16.520000 If I give my laptop just this 32 bit number, 10101010101, how does it 0:11:16.520000 --> 0:11:22.180000 know what portion on the phone front end belongs to its network and what 0:11:22.180000 --> 0:11:27.340000 portion on the back end belongs to just it as a unique identifier? 0:11:27.340000 --> 0:11:30.560000 That is where we have something called a subnet mask. 0:11:30.560000 --> 0:11:37.040000 So every IP address has to come with an additional number called a subnet 0:11:37.040000 --> 0:11:44.080000 mask. So for example, if I took this IP address in binary and then I gave 0:11:44.080000 --> 0:11:49.080000 it. This subnet mask, let's see here. 0:11:49.080000 --> 0:11:54.080000 I'll do the subnet mask in green beneath here. 0:11:54.080000 --> 0:11:55.500000 If I said, okay. 0:11:55.500000 --> 0:11:58.440000 Here is your subnet mask. 0:11:58.440000 --> 0:12:06.520000 Once again, if you were curious about how this works, I invite you to 0:12:06.520000 --> 0:12:10.780000 watch the CCNA videos, especially the section on IP addressing and subnetting. 0:12:10.780000 --> 0:12:17.500000 But in short, these bits here in black represent these are the IP address 0:12:17.500000 --> 0:12:21.320000 on a laptop or a server or a PC or whatever. 0:12:21.320000 --> 0:12:26.200000 I'm not going to count them up, but let's just assume it's 32 bits long. 0:12:26.200000 --> 0:12:35.980000 And that IP address has to also have a subnet mask, which are these bits 0:12:35.980000 --> 0:12:40.640000 right here. And the way the subnet mask is interpreted is that each bit 0:12:40.640000 --> 0:12:45.320000 in the subnet mask is compared against a bit in the IP address. 0:12:45.320000 --> 0:12:49.660000 If the bit in a subnet mask is a one, that means the corresponding bit 0:12:49.660000 --> 0:12:52.720000 in the actual address itself is a network bit. 0:12:52.720000 --> 0:12:55.500000 It belongs to that group of bits at the front that's common among all 0:12:55.500000 --> 0:12:58.700000 the devices. So in this particular case in the subnet mask, because the 0:12:58.700000 --> 0:13:04.120000 first eight bits are turned to ones, that tells my laptop of this 32 bit 0:13:04.120000 --> 0:13:08.740000 number, the first eight bits I share with all the other devices in my 0:13:08.740000 --> 0:13:11.700000 group. Why do we care? 0:13:11.700000 --> 0:13:13.220000 Why do we need to know that? 0:13:13.220000 --> 0:13:15.180000 Let's go back to this. 0:13:15.180000 --> 0:13:21.840000 So let's say in payroll, I said, OK, here in payroll, what we're going 0:13:21.840000 --> 0:13:27.320000 to do is we're going to say everybody in payroll starts out with, let's 0:13:27.320000 --> 0:13:34.580000 say, 30 dot 30 dot something dot something slash 16. 0:13:34.580000 --> 0:13:38.500000 This is a shorthand way of representing a subnet mask saying, OK, of this 0:13:38.500000 --> 0:13:44.180000 of my IP address, the first 16 bits represent the network portion. 0:13:44.180000 --> 0:13:47.840000 So that means that everybody in here, Bob, Sally, Sue and the server would 0:13:47.840000 --> 0:13:50.340000 have an IP address beginning with 30 dot 30. 0:13:50.340000 --> 0:13:59.700000 And then the remaining bits would be just, you know, something else. 0:13:59.700000 --> 0:14:03.380000 Those are the host bits. 0:14:03.380000 --> 0:14:07.020000 And they each have a subnet mask as well, because without a subnet mask, 0:14:07.020000 --> 0:14:10.480000 they would have no way of knowing, hey, what network am I in? 0:14:10.480000 --> 0:14:13.620000 Where do I draw the dividing line between my network bits and my host 0:14:13.620000 --> 0:14:21.120000 bits? And down here in marketing, those guys are going to need an IP network. 0:14:21.120000 --> 0:14:29.800000 Let's say we give them 30 dot 40 dot x dot x slash 16. 0:14:29.800000 --> 0:14:35.920000 Notice with slash 16 that says of your IP address, the first half of it 0:14:35.920000 --> 0:14:38.040000 is your network. 0:14:38.040000 --> 0:14:41.060000 So everybody here has an address beginning with 30 30. 0:14:41.060000 --> 0:14:44.640000 Well, everybody down here in marketing is going to have an address beginning 0:14:44.640000 --> 0:15:01.700000 with 30 dot 40. That's a totally different pattern in binary. 0:15:01.700000 --> 0:15:05.500000 Okay, so with our IP addressing now firmly in place. 0:15:05.500000 --> 0:15:16.820000 If Kevin down here, if on Kevin, I cause his browser or his email or whatever 0:15:16.820000 --> 0:15:19.440000 it is to create some data. 0:15:19.440000 --> 0:15:26.680000 And the destination address of that data is 30 dot 40 dot anything. 0:15:26.680000 --> 0:15:31.520000 Kevin's going to say, oh, well, my IP address begins with 30 dot 40. 0:15:31.520000 --> 0:15:36.320000 I've been told via my subnet mask that 30 dot 40 is the group I'm in. 0:15:36.320000 --> 0:15:40.740000 The destination I'm trying to reach is also in my same group. 0:15:40.740000 --> 0:15:43.260000 It's 30 dot 40. Great. 0:15:43.260000 --> 0:15:45.620000 I can just send my ethernet frame directly to that guy. 0:15:45.620000 --> 0:15:49.180000 I'll just figure out what his MAC address is and send it directly to him. 0:15:49.180000 --> 0:15:53.980000 But now if Kevin wanted to reach a server up here, now Kevin is creating 0:15:53.980000 --> 0:16:00.000000 a packet with a destination address of 30 dot 30 dot six dot six. 0:16:00.000000 --> 0:16:05.440000 Kevin's laptop is going to say, hmm, I'm in the 30 dot 40 group, but the 0:16:05.440000 --> 0:16:09.860000 destination of this data that I need to send is not in the 30 dot 40 group. 0:16:09.860000 --> 0:16:11.840000 It's in something else. 0:16:11.840000 --> 0:16:13.880000 In this case, 30 dot 30. 0:16:13.880000 --> 0:16:16.620000 That's not me. That's not my group. 0:16:16.620000 --> 0:16:21.840000 That is the trigger for Kevin's laptop to say, okay, since this data is 0:16:21.840000 --> 0:16:26.660000 not in my group, I need to send it to somebody in my group who knows how 0:16:26.660000 --> 0:16:29.020000 to get it to other groups. 0:16:29.020000 --> 0:16:31.040000 And that's the router. 0:16:31.040000 --> 0:16:35.520000 So in this particular case, any time your laptop, your tablet, your smartphone, 0:16:35.520000 --> 0:16:39.860000 your PC creates data, first thing it's going to do is going to take a 0:16:39.860000 --> 0:16:44.320000 look at the IP address of itself, which is the source. 0:16:44.320000 --> 0:16:47.880000 Compare that to the IP address of the destination and it's going to ask 0:16:47.880000 --> 0:16:49.660000 itself this very simple question. 0:16:49.660000 --> 0:16:54.120000 Is the destination I'm trying to reach in the same layer two network as 0:16:54.120000 --> 0:16:59.920000 me? If the answer is no, that is the trigger for that laptop, that PC, 0:16:59.920000 --> 0:17:04.360000 that server to say, I need to send this data to the default gateway. 0:17:04.360000 --> 0:17:06.300000 I don't know how to get to that remote network. 0:17:06.300000 --> 0:17:08.980000 It could be 10,000 miles away for all I know. 0:17:08.980000 --> 0:17:10.380000 I'm going to send to my default gateway. 0:17:10.380000 --> 0:17:12.440000 In other words, my router. 0:17:12.440000 --> 0:17:15.420000 And I'll just assume the router knows how to get it there. 0:17:15.420000 --> 0:17:20.500000 So we've also learned that an IP address is a logical address given to 0:17:20.500000 --> 0:17:24.800000 a network. In other words, when I was designing this network, I didn't 0:17:24.800000 --> 0:17:27.420000 really have any choice over the Mac addresses. 0:17:27.420000 --> 0:17:30.620000 The Mac addresses came with the Ethernet NIC card, which was built into 0:17:30.620000 --> 0:17:33.280000 the laptop, or built into the server. 0:17:33.280000 --> 0:17:37.420000 I didn't have any control over what my Mac addresses were going to be. 0:17:37.420000 --> 0:17:41.020000 They were just put in there by the manufacturer of the NIC card. 0:17:41.020000 --> 0:17:45.500000 But as a network administrator, I do have control over what IP addressing 0:17:45.500000 --> 0:17:51.060000 I want to use. Also, the Mac address stays with you. 0:17:51.060000 --> 0:17:56.060000 In other words, if Bob unplugged from the switch port, and then he moved 0:17:56.060000 --> 0:18:02.180000 to a blue switch port, well, he's changed VLANs, but his Mac address is 0:18:02.180000 --> 0:18:03.140000 not going to change. 0:18:03.140000 --> 0:18:05.040000 His Mac address is burned into his NIC card. 0:18:05.040000 --> 0:18:06.860000 It's always going to be 1-1. 0:18:06.860000 --> 0:18:09.180000 That's the Mac address of his device. 0:18:09.180000 --> 0:18:13.420000 However, if Bob now moves into the blue group, Bob should no longer have 0:18:13.420000 --> 0:18:15.940000 a 30.30 IP address. 0:18:15.940000 --> 0:18:18.300000 He's not in the 30 .30 group anymore. 0:18:18.300000 --> 0:18:20.880000 He's now in the 30.40 group. 0:18:20.880000 --> 0:18:27.560000 So a Mac address at layer two doesn't really tell you where you are in 0:18:27.560000 --> 0:18:33.720000 the network. It just says, this is my name, and that's all I know. 0:18:33.720000 --> 0:18:38.840000 But an IP address is like an address you put on an envelope, right? 0:18:38.840000 --> 0:18:42.400000 When you're mailing something, it's a geographical indicator. 0:18:42.400000 --> 0:18:45.020000 It indicates where in the network something is. 0:18:45.020000 --> 0:18:46.400000 So it's logical. 0:18:46.400000 --> 0:18:48.960000 In other words, the IP address does not stick with you. 0:18:48.960000 --> 0:18:53.800000 The IP address you have represents where in the network you are right 0:18:53.800000 --> 0:18:57.120000 now. And if you move to another part of the network, you'll probably get 0:18:57.120000 --> 0:19:00.020000 a different IP address because now you're in a different group. 0:19:00.020000 --> 0:19:03.900000 IP version four addresses are comprised of four octets. 0:19:03.900000 --> 0:19:07.660000 That's right. So when I was talking about the bits here, every grouping 0:19:07.660000 --> 0:19:13.940000 of eight bits is considered a byte, otherwise known as an octet. 0:19:13.940000 --> 0:19:17.420000 An octet. So here we have four octets. 0:19:17.420000 --> 0:19:18.780000 That was the first one. 0:19:18.780000 --> 0:19:20.280000 That's the second one. 0:19:20.280000 --> 0:19:21.960000 That's the third one. 0:19:21.960000 --> 0:19:24.520000 And that's the fourth one. 0:19:24.520000 --> 0:19:29.040000 And then lastly, when we're configuring IP addresses in devices, or when 0:19:29.040000 --> 0:19:32.420000 we're reading about IP addresses, we don't do it like this. 0:19:32.420000 --> 0:19:36.020000 Your fingers would fall off in no time if you had to configure IP addresses 0:19:36.020000 --> 0:19:40.360000 in binary, and your brain would explode and turn into mush if you had 0:19:40.360000 --> 0:19:43.560000 to understand IP addresses in binary. 0:19:43.560000 --> 0:19:45.860000 Laptops and computers have no problem with this. 0:19:45.860000 --> 0:19:48.180000 As human beings, we can't do it. 0:19:48.180000 --> 0:19:52.660000 So what we do is we convert these binary numbers into what's called dotted 0:19:52.660000 --> 0:19:58.780000 decimal. So all this time when I've been writing my IP addresses as 30 0:19:58.780000 --> 0:20:05.600000 .30.1.1, basically what that's saying is 30 is some eight bit number. 0:20:05.600000 --> 0:20:07.220000 0011 blah blah blah. 0:20:07.220000 --> 0:20:08.440000 That's the number 30. 0:20:08.440000 --> 0:20:10.700000 The next 30 is another eight bit number. 0:20:10.700000 --> 0:20:13.100000 77 is another eight bit number. 0:20:13.100000 --> 0:20:15.640000 123 is another eight bit number. 0:20:15.640000 --> 0:20:19.580000 So this is called dotted decimal notation. 0:20:19.580000 --> 0:20:24.460000 But the actual laptop or computer converts that into binary. 0:20:24.460000 --> 0:20:29.280000 Now lastly, the last topic in this particular set is what is a subnet. 0:20:29.280000 --> 0:20:33.700000 We had to explain what an IP address is, what is a subnet? 0:20:33.700000 --> 0:20:39.440000 I intentionally designed this topology where everything started with the 0:20:39.440000 --> 0:20:42.380000 number 30. Why did I do that? 0:20:42.380000 --> 0:20:46.380000 Well, chances are you're not just going to make up your own IP addressing. 0:20:46.380000 --> 0:20:51.340000 Now if your network has no connectivity to the outside world, if you just 0:20:51.340000 --> 0:20:55.320000 have your own self-contained little island of a network, yeah, you can 0:20:55.320000 --> 0:20:57.240000 make up whatever IP addressing you want. 0:20:57.240000 --> 0:20:59.800000 But that probably doesn't describe most of you. 0:20:59.800000 --> 0:21:03.220000 Most of you, your networks have to connect to the internet or connect 0:21:03.220000 --> 0:21:05.540000 to, yeah, probably the internet. 0:21:05.540000 --> 0:21:09.460000 Which means you're going to go to your internet service provider and they're 0:21:09.460000 --> 0:21:13.160000 going to give you a network and they're going to charge you for it, right? 0:21:13.160000 --> 0:21:16.500000 Charge you a pretty little penny every single month on the monthly bill. 0:21:16.500000 --> 0:21:22.000000 So when I went to my ISP, they told me, just as an example here, they 0:21:22.000000 --> 0:21:27.460000 said, okay, we're going to give you 30 slash eight. 0:21:27.460000 --> 0:21:31.580000 In other words, from the ISP's perspective, so here I am, I'm the ISP, 0:21:31.580000 --> 0:21:34.920000 I have a router right here, and this router has a cable modem or a DSL 0:21:34.920000 --> 0:21:38.940000 connection down to you and your company. 0:21:38.940000 --> 0:21:44.600000 So from my perspective, everything that starts with the number 30 lives 0:21:44.600000 --> 0:21:47.060000 over there, lives with you. 0:21:47.060000 --> 0:21:50.620000 All your devices, I don't care how many devices you have, all their IP 0:21:50.620000 --> 0:21:53.400000 addresses have to begin with the number 30. 0:21:53.400000 --> 0:21:56.840000 So I'm going to advertise to the outside world and say, hey everybody, 0:21:56.840000 --> 0:22:01.180000 if you ever need to get to destination 30, come to me, I know where it 0:22:01.180000 --> 0:22:05.920000 is. And when packets come to me from India and Mongolia and Russia and 0:22:05.920000 --> 0:22:09.300000 Indiana, if they're going to a destination IP address that has the number 0:22:09.300000 --> 0:22:13.620000 30, starts with 30, I'll send it down to you. 0:22:13.620000 --> 0:22:18.360000 Now that's fine for me, but for you, you've got all these different VLANs, 0:22:18.360000 --> 0:22:23.040000 payroll, marketing, engineering, you know, the kitchen staff, every single 0:22:23.040000 --> 0:22:27.060000 one of those VLANs needs a unique network. 0:22:27.060000 --> 0:22:32.260000 Now if you just put all devices beginning with 30 in one network, if you 0:22:32.260000 --> 0:22:35.340000 just said, okay, marketing, you're all going to begin with the number 0:22:35.340000 --> 0:22:38.720000 30. What do I do for payroll? 0:22:38.720000 --> 0:22:40.720000 What do I do for engineering? 0:22:40.720000 --> 0:22:45.380000 I guess I got to go back to my ISP and pay them more money for a second 0:22:45.380000 --> 0:22:49.540000 network and a third network and a fourth network. 0:22:49.540000 --> 0:22:52.460000 Now they would love that because the more networks they sell you, the 0:22:52.460000 --> 0:22:54.600000 more their bill is going to be every single month. 0:22:54.600000 --> 0:23:02.660000 But in reality, you might say, hey, with 30, that means that the remaining 0:23:02.660000 --> 0:23:07.500000 24 bits here are whatever I want them to be. 0:23:07.500000 --> 0:23:11.260000 That's a lot of combinations of numbers. 0:23:11.260000 --> 0:23:14.640000 24 bits, each one of those bits can be a zero or a one. 0:23:14.640000 --> 0:23:18.800000 How many combinations can you come up with with 24 bits? 0:23:18.800000 --> 0:23:22.000000 That's two to the power of 24. 0:23:22.000000 --> 0:23:24.240000 That's millions and millions. 0:23:24.240000 --> 0:23:25.920000 That's a huge number. 0:23:25.920000 --> 0:23:28.760000 You might say, well, why don't I do this? 0:23:28.760000 --> 0:23:33.300000 I know that everything in my network has to begin with 30, but why don't 0:23:33.300000 --> 0:23:35.020000 I do what Keith designed right here? 0:23:35.020000 --> 0:23:38.520000 Why don't I say, hey, in payroll, all of your IP addresses are going to 0:23:38.520000 --> 0:23:41.720000 start with 30, 30. 0:23:41.720000 --> 0:23:43.260000 Down here, marketing. 0:23:43.260000 --> 0:23:46.960000 All of your IP addresses are going to start with 30, 40. 0:23:46.960000 --> 0:23:51.020000 What I have done now is created subnets. 0:23:51.020000 --> 0:23:55.860000 I got one network from my ISP, the 30 network, and I've subdivided it 0:23:55.860000 --> 0:23:57.400000 into different pieces. 0:23:57.400000 --> 0:24:01.620000 I've said this portion of the 30 network, 30.40, is going to be right 0:24:01.620000 --> 0:24:04.480000 here. And everything here is going to start with 30.40. 0:24:04.480000 --> 0:24:10.240000 Another subnet, another portion of the 30 network, maybe 30.75 will be 0:24:10.240000 --> 0:24:15.680000 over here. Another subnet, 30 .150, that will go down here. 0:24:15.680000 --> 0:24:21.460000 So a subnet is a network that was derived or taken from a much larger 0:24:21.460000 --> 0:24:26.400000 network. It's a portion or a piece of a much larger network. 0:24:26.400000 --> 0:24:31.360000 So from the ISP's perspective, I say you own everything beginning with 0:24:31.360000 --> 0:24:35.140000 30. I don't care what you do with that addressing space, those millions 0:24:35.140000 --> 0:24:37.320000 and millions and millions of addresses. 0:24:37.320000 --> 0:24:39.640000 All I care about is that you just use the number 30. 0:24:39.640000 --> 0:24:44.360000 Now if you want to take that up and carve it up into 25 different subnets 0:24:44.360000 --> 0:24:47.780000 or 200 different subnets, I don't care. 0:24:47.780000 --> 0:24:51.740000 As long as they all begin with the number 30, that's all I care about. 0:24:51.740000 --> 0:24:53.220000 So that's what a subnet is. 0:24:53.220000 --> 0:24:58.920000 A subnet is a smaller network that is taken from a larger overall network. 0:24:58.920000 --> 0:25:00.860000 And that concludes this video.