1 1 00:00:00,150 --> 00:00:02,740 Internet Protocol version 4 addressing. 2 2 00:00:02,740 --> 00:00:03,650 In this lesson, 3 3 00:00:03,650 --> 00:00:05,610 we're going to talk about IPv4 4 4 00:00:05,610 --> 00:00:07,960 or Internet Protocol version 4. 5 5 00:00:07,960 --> 00:00:10,130 IPv4 is extremely popular 6 6 00:00:10,130 --> 00:00:12,400 and is the most common type of IP addressing 7 7 00:00:12,400 --> 00:00:13,810 that's used in our networks. 8 8 00:00:13,810 --> 00:00:15,570 In fact, if you're like most people, 9 9 00:00:15,570 --> 00:00:18,400 you've already seen an IPv4 address before. 10 10 00:00:18,400 --> 00:00:19,233 When you look at them, 11 11 00:00:19,233 --> 00:00:21,350 they're written as a series of four decimal numbers 12 12 00:00:21,350 --> 00:00:22,710 separated by dots. 13 13 00:00:22,710 --> 00:00:26,910 Some examples of this are IPv4 addresses like 10.1.2.3 14 14 00:00:26,910 --> 00:00:31,190 or 172.21.243.67. 15 15 00:00:31,190 --> 00:00:32,200 As you can see, 16 16 00:00:32,200 --> 00:00:34,740 each IPv4 address is made up of four parts 17 17 00:00:34,740 --> 00:00:36,050 to form that address. 18 18 00:00:36,050 --> 00:00:38,660 This is known as a dotted-decimal notation. 19 19 00:00:38,660 --> 00:00:39,840 When you're referring to each of those 20 20 00:00:39,840 --> 00:00:41,010 four individual parts, 21 21 00:00:41,010 --> 00:00:42,370 we call this an octet 22 22 00:00:42,370 --> 00:00:44,100 because they each have a decimal number 23 23 00:00:44,100 --> 00:00:46,610 that's used to represent an 8-bit number. 24 24 00:00:46,610 --> 00:00:48,670 Because these decimal numbers represent an 8-bit 25 25 00:00:48,670 --> 00:00:50,350 or eight binary digits, 26 26 00:00:50,350 --> 00:00:52,470 this means that they can only represent a value 27 27 00:00:52,470 --> 00:00:56,290 from zero to 255 in each of those four positions. 28 28 00:00:56,290 --> 00:00:58,330 Now, when all four octets are combined, 29 29 00:00:58,330 --> 00:01:01,390 we have four octets that contain eight bits each, 30 30 00:01:01,390 --> 00:01:04,630 for a total of 32 bits of total addressable space 31 31 00:01:04,630 --> 00:01:07,050 when using an IPv4 address. 32 32 00:01:07,050 --> 00:01:08,080 Now, for example, 33 33 00:01:08,080 --> 00:01:13,010 if I have the IPv4 address of 192.168.1.4, 34 34 00:01:13,010 --> 00:01:15,190 this is written in dotted-decimal notation 35 35 00:01:15,190 --> 00:01:17,420 to make it easier for us as humans to read it. 36 36 00:01:17,420 --> 00:01:18,800 But in reality, 37 37 00:01:18,800 --> 00:01:23,590 it's actually 11000000.10101000.00000001.00000100 38 38 00:01:34,810 --> 00:01:37,330 if I put its into true binary form. 39 39 00:01:37,330 --> 00:01:38,270 As you can see, 40 40 00:01:38,270 --> 00:01:39,910 being able to use dotted-decimal notation 41 41 00:01:39,910 --> 00:01:42,820 is a lot easier for us to read and to type. 42 42 00:01:42,820 --> 00:01:45,310 And therefore, it's less prone to us making mistakes 43 43 00:01:45,310 --> 00:01:47,300 because as humans entering these numbers 44 44 00:01:47,300 --> 00:01:49,140 into our network devices using binary 45 45 00:01:49,140 --> 00:01:51,380 would just be a big issue for us. 46 46 00:01:51,380 --> 00:01:53,170 We just don't think that way. 47 47 00:01:53,170 --> 00:01:58,080 Now, when we see an IP address like 192.168.1.4, 48 48 00:01:58,080 --> 00:02:00,700 it's actually being broken down into two portions 49 49 00:02:00,700 --> 00:02:04,740 by using a second 32-bit number known as a subnet mask. 50 50 00:02:04,740 --> 00:02:06,730 Now, one part of the IPv4 address 51 51 00:02:06,730 --> 00:02:08,610 is used to identify the network portion 52 52 00:02:08,610 --> 00:02:09,500 and the other part 53 53 00:02:09,500 --> 00:02:11,850 is going to be used to identify the host portion. 54 54 00:02:11,850 --> 00:02:13,180 When you look at a subnet mask, 55 55 00:02:13,180 --> 00:02:15,760 it's going to look a lot like an IPv4 address, 56 56 00:02:15,760 --> 00:02:17,740 but if you convert it to binary, 57 57 00:02:17,740 --> 00:02:18,573 you're going to see that it has 58 58 00:02:18,573 --> 00:02:21,000 a continuous strings of ones or zeros 59 59 00:02:21,000 --> 00:02:22,040 to identify the network 60 60 00:02:22,040 --> 00:02:24,010 and host portions of that address 61 61 00:02:24,010 --> 00:02:26,090 being used by the client or device. 62 62 00:02:26,090 --> 00:02:31,090 So if I have a subnet mask like 255.255.255.0, 63 63 00:02:31,280 --> 00:02:34,290 this is known as a default class C subnet mask. 64 64 00:02:34,290 --> 00:02:36,330 Now, don't worry about classes just yet, 65 65 00:02:36,330 --> 00:02:38,600 we are going to cover them more in just a moment. 66 66 00:02:38,600 --> 00:02:39,680 For now, I just want you to see 67 67 00:02:39,680 --> 00:02:41,540 what a subnet mask looks like. 68 68 00:02:41,540 --> 00:02:44,420 Now, if I converted this into binary, 69 69 00:02:44,420 --> 00:02:46,610 each of those octets that are 255 70 70 00:02:46,610 --> 00:02:48,260 are going to be written as 11111111. 71 71 00:02:50,100 --> 00:02:52,303 So I'm going to get 11111111.11111111.11111111. 72 72 00:03:00,450 --> 00:03:01,923 and then 00000000. 73 73 00:03:04,220 --> 00:03:06,060 This is because in binary, 74 74 00:03:06,060 --> 00:03:08,470 eight ones is going to equal 255 75 75 00:03:08,470 --> 00:03:09,690 when I read it in decimal. 76 76 00:03:09,690 --> 00:03:11,300 And if I have eight zeros in binary 77 77 00:03:11,300 --> 00:03:13,750 that is going to equal zero in decimal. 78 78 00:03:13,750 --> 00:03:16,480 Again, don't worry too much about this conversion just yet. 79 79 00:03:16,480 --> 00:03:18,730 We are going to do a lot of these different conversions 80 80 00:03:18,730 --> 00:03:20,900 and math problems in a separate video lesson 81 81 00:03:20,900 --> 00:03:23,090 when we talk about computer mathematics. 82 82 00:03:23,090 --> 00:03:24,830 Now, when you look at this number, 83 83 00:03:24,830 --> 00:03:27,490 if you see a one in the binary of that subnet mask, 84 84 00:03:27,490 --> 00:03:29,670 this means it's part of the network portion 85 85 00:03:29,670 --> 00:03:31,130 of the IP address. 86 86 00:03:31,130 --> 00:03:33,860 If I see a zero in the binary portion of the subnet mask, 87 87 00:03:33,860 --> 00:03:35,620 this means it's part of the host portion 88 88 00:03:35,620 --> 00:03:37,130 of the IPv4 address. 89 89 00:03:37,130 --> 00:03:40,527 So let's put this together by showing both an IPv4 address 90 90 00:03:40,527 --> 00:03:42,370 and a subnet mask together. 91 91 00:03:42,370 --> 00:03:45,893 First, we have our IPv4 address of 192.168.1.4. 92 92 00:03:47,800 --> 00:03:49,460 Next we have our subnet mask 93 93 00:03:49,460 --> 00:03:54,050 underneath it with 255.255.255.0. 94 94 00:03:54,050 --> 00:03:56,460 Now, everywhere I see that 255, 95 95 00:03:56,460 --> 00:03:58,980 this is going to represent a one in binary. 96 96 00:03:58,980 --> 00:04:01,240 So this becomes part of the network portion 97 97 00:04:01,240 --> 00:04:03,140 of that IPv4 address. 98 98 00:04:03,140 --> 00:04:07,130 If I use this example, 192.168.1.4, 99 99 00:04:07,130 --> 00:04:11,520 the 198.168.1, that is part of the network. 100 100 00:04:11,520 --> 00:04:16,420 Now, I can do anything that starts with 192.168.1.something 101 101 00:04:16,420 --> 00:04:19,020 and it would all be addressable by the same local network 102 102 00:04:19,020 --> 00:04:22,260 because they all share this same network portion. 103 103 00:04:22,260 --> 00:04:23,870 Now, when I get to the second part, 104 104 00:04:23,870 --> 00:04:25,540 anytime I see those zeros, 105 105 00:04:25,540 --> 00:04:27,950 this represents all zeros in binary. 106 106 00:04:27,950 --> 00:04:31,780 So that's going to be the host portion of that IPv4 address. 107 107 00:04:31,780 --> 00:04:35,260 In this case, that is the .4 portion of this address, 108 108 00:04:35,260 --> 00:04:36,930 which is going to represent the host. 109 109 00:04:36,930 --> 00:04:40,560 That host could be a server, a desktop, a laptop, a tablet, 110 110 00:04:40,560 --> 00:04:42,800 a smartphone or any other network device. 111 111 00:04:42,800 --> 00:04:44,110 It really doesn't matter. 112 112 00:04:44,110 --> 00:04:46,230 But when we talk about this .4 device, 113 113 00:04:46,230 --> 00:04:47,770 that is a single host. 114 114 00:04:47,770 --> 00:04:50,720 When I talk about the 192.168.1, 115 115 00:04:50,720 --> 00:04:55,330 that is the network that can contain up to 254 devices. 116 116 00:04:55,330 --> 00:04:59,670 So if I have a device like 192.168.1.50 117 117 00:04:59,670 --> 00:05:03,560 with a subnet of 255.255.255.0 118 118 00:05:03,560 --> 00:05:06,050 that device is also in the same network 119 119 00:05:06,050 --> 00:05:09,340 as our 192.168.1.4 device, 120 120 00:05:09,340 --> 00:05:11,840 and they can communicate with each other using a switch 121 121 00:05:11,840 --> 00:05:13,340 and they wouldn't have to use a router 122 122 00:05:13,340 --> 00:05:18,340 because they both share the same network portion, 192.168.1. 123 123 00:05:18,490 --> 00:05:19,540 Now, on the other hand, 124 124 00:05:19,540 --> 00:05:23,970 let's assume I have a device like 192.168.0.100 125 125 00:05:23,970 --> 00:05:27,970 with a subnet of 255.255.255.0, 126 126 00:05:27,970 --> 00:05:30,160 that device is on a different network, 127 127 00:05:30,160 --> 00:05:34,720 specifically, it's on the 192.168.0.something network. 128 128 00:05:34,720 --> 00:05:37,920 So we cannot communicate that from our original device 129 129 00:05:37,920 --> 00:05:42,350 at 192.168.1.4 without leaving our network 130 130 00:05:42,350 --> 00:05:44,820 and routing our traffic over to this new network, 131 131 00:05:44,820 --> 00:05:48,370 this 192.168.0.something network. 132 132 00:05:48,370 --> 00:05:50,440 This is why we need to have a router. 133 133 00:05:50,440 --> 00:05:52,360 Now, if this doesn't quite make sense yet, 134 134 00:05:52,360 --> 00:05:53,810 don't worry too much. 135 135 00:05:53,810 --> 00:05:55,740 We are going to dive deeper into subnetting 136 136 00:05:55,740 --> 00:05:57,840 and you're going to actually calculate subnet mast 137 137 00:05:57,840 --> 00:06:00,360 and things like that to learn how routing works. 138 138 00:06:00,360 --> 00:06:02,810 Right now, we have barely just scratched the surface 139 139 00:06:02,810 --> 00:06:04,260 in the examples we talked about. 140 140 00:06:04,260 --> 00:06:05,480 And I just wanted to get you the idea 141 141 00:06:05,480 --> 00:06:07,510 and introduce you to this concept. 142 142 00:06:07,510 --> 00:06:09,660 Now, the next concept that we need to talk about 143 143 00:06:09,660 --> 00:06:11,520 is that an IPv4 addresses 144 144 00:06:11,520 --> 00:06:13,380 and how they're broken up into classes 145 145 00:06:13,380 --> 00:06:15,000 or groupings or ranges 146 146 00:06:15,000 --> 00:06:17,010 that can be used for different purposes. 147 147 00:06:17,010 --> 00:06:20,220 Now, each class has its own default subnet mask as well. 148 148 00:06:20,220 --> 00:06:21,340 When we talk about classes, 149 149 00:06:21,340 --> 00:06:23,270 we identify these by a letter. 150 150 00:06:23,270 --> 00:06:27,430 These letters are A, B, C, D, and E. 151 151 00:06:27,430 --> 00:06:30,160 Now, to identify the class for a given IP address, 152 152 00:06:30,160 --> 00:06:32,700 you just need to look at the first octet. 153 153 00:06:32,700 --> 00:06:36,410 If that first octet begins with a number between 1 and 127, 154 154 00:06:36,410 --> 00:06:38,297 it's going to be considered a class A address, 155 155 00:06:38,297 --> 00:06:42,930 and it has a default subnet mask of 255.0.0.0. 156 156 00:06:42,930 --> 00:06:45,010 This means the network portion of that address 157 157 00:06:45,010 --> 00:06:46,690 is just the first octet, 158 158 00:06:46,690 --> 00:06:48,550 and the second, third and fourth octets 159 159 00:06:48,550 --> 00:06:50,640 are going to make up the host portion. 160 160 00:06:50,640 --> 00:06:52,850 This means that with a class A network, 161 161 00:06:52,850 --> 00:06:57,760 we can have 256 times 256 times 256 hosts 162 162 00:06:57,760 --> 00:06:59,120 on a single network, 163 163 00:06:59,120 --> 00:07:01,880 which means there are 16.7 million 164 164 00:07:01,880 --> 00:07:03,500 possible host IP addresses 165 165 00:07:03,500 --> 00:07:05,820 available for a single network address portion 166 166 00:07:05,820 --> 00:07:07,610 assigned in the class A. 167 167 00:07:07,610 --> 00:07:09,110 Now, our second class we have 168 168 00:07:09,110 --> 00:07:10,670 occurs when we have that first octet 169 169 00:07:10,670 --> 00:07:14,360 beginning with a number between 128 and 191. 170 170 00:07:14,360 --> 00:07:16,560 This would be considered a class B address, 171 171 00:07:16,560 --> 00:07:21,560 and it will have a default subnet mask of 255.255.0.0. 172 172 00:07:21,710 --> 00:07:24,000 This means that the network portion of this address 173 173 00:07:24,000 --> 00:07:26,120 is going to be the first and second octets, 174 174 00:07:26,120 --> 00:07:27,520 and the third and fourth octet 175 175 00:07:27,520 --> 00:07:29,560 are going to make up the host portion. 176 176 00:07:29,560 --> 00:07:31,530 This means that for a class B network, 177 177 00:07:31,530 --> 00:07:36,030 we can have up to 256 times 256 hosts on a single network. 178 178 00:07:36,030 --> 00:07:41,030 And that means we get 65,536 possible host IP addresses 179 179 00:07:41,260 --> 00:07:43,380 available for a single network address portion 180 180 00:07:43,380 --> 00:07:45,680 assigned within a class B. 181 181 00:07:45,680 --> 00:07:48,380 Now, the third class we have occurs when the first octet 182 182 00:07:48,380 --> 00:07:52,150 begins with a number between 192 and 223. 183 183 00:07:52,150 --> 00:07:54,170 This is considered a class C address, 184 184 00:07:54,170 --> 00:07:59,170 and it has a default subnet mask of 255.255.255.0. 185 185 00:07:59,470 --> 00:08:01,360 This means that the network portion of the address 186 186 00:08:01,360 --> 00:08:04,140 is going to be the first, second and third octet. 187 187 00:08:04,140 --> 00:08:07,290 And we save that fourth octet for the host portion. 188 188 00:08:07,290 --> 00:08:09,130 This means that for a class C network, 189 189 00:08:09,130 --> 00:08:12,460 you can only have 256 hosts on a single network. 190 190 00:08:12,460 --> 00:08:16,160 And this means there are only 256 possible host IP addresses 191 191 00:08:16,160 --> 00:08:18,200 available for a single network address portion 192 192 00:08:18,200 --> 00:08:19,580 that's being assigned. 193 193 00:08:19,580 --> 00:08:22,310 Now the fourth class we have occurs when the first octet 194 194 00:08:22,310 --> 00:08:25,820 begins with a number between 224 and 239. 195 195 00:08:25,820 --> 00:08:28,350 This is considered a class D address. 196 196 00:08:28,350 --> 00:08:29,610 Now, a class D address 197 197 00:08:29,610 --> 00:08:32,280 does not have any subnet mask assigned to it. 198 198 00:08:32,280 --> 00:08:34,950 This is because class D addresses are special 199 199 00:08:34,950 --> 00:08:38,570 and they're reserved for multicasting or multicast routing. 200 200 00:08:38,570 --> 00:08:41,200 Now, a multicast address is a logical identifier 201 201 00:08:41,200 --> 00:08:43,290 for a group of hosts in a computer network 202 202 00:08:43,290 --> 00:08:45,860 that are already going to be available to process datagrams 203 203 00:08:45,860 --> 00:08:48,070 or frames intended to be multicast 204 204 00:08:48,070 --> 00:08:49,930 for a designated network service. 205 205 00:08:49,930 --> 00:08:52,300 So the actual multicast address 206 206 00:08:52,300 --> 00:08:54,510 doesn't have to align with a single host, 207 207 00:08:54,510 --> 00:08:57,040 but instead, it aligns with a group of hosts. 208 208 00:08:57,040 --> 00:08:58,960 When you think about a multicast address, 209 209 00:08:58,960 --> 00:09:01,470 I want you to think about it like a group chat on Facebook. 210 210 00:09:01,470 --> 00:09:02,810 You might have a group chat name, 211 211 00:09:02,810 --> 00:09:04,750 in our case, a multicast address. 212 212 00:09:04,750 --> 00:09:07,270 And when you send a message to your group chat's name, 213 213 00:09:07,270 --> 00:09:08,440 all of the members of that group 214 214 00:09:08,440 --> 00:09:10,260 are going to get a copy of that message. 215 215 00:09:10,260 --> 00:09:12,710 Well, the same thing is going to happen in multicast 216 216 00:09:12,710 --> 00:09:14,550 when we're using IPv4. 217 217 00:09:14,550 --> 00:09:16,760 We're going to talk more about multicasting later on 218 218 00:09:16,760 --> 00:09:18,650 when we discuss the different types of data flows 219 219 00:09:18,650 --> 00:09:20,220 within IPv4. 220 220 00:09:20,220 --> 00:09:21,053 But for now, 221 221 00:09:21,053 --> 00:09:22,640 this is the idea of what you need to understand 222 222 00:09:22,640 --> 00:09:23,700 with multicasting. 223 223 00:09:23,700 --> 00:09:25,150 I sent it from one person 224 224 00:09:25,150 --> 00:09:27,820 and it goes to multiple people all at the same time. 225 225 00:09:27,820 --> 00:09:30,120 Now, the fifth class we have occurs when the first octet 226 226 00:09:30,120 --> 00:09:33,410 begins with a number between 240 and 255. 227 227 00:09:33,410 --> 00:09:35,530 This is called a class E address 228 228 00:09:35,530 --> 00:09:38,280 and it also has no default subnet mask. 229 229 00:09:38,280 --> 00:09:41,010 This is because class E addresses are also special. 230 230 00:09:41,010 --> 00:09:41,850 In this case, 231 231 00:09:41,850 --> 00:09:44,530 they're reserved for experimental purposes for research 232 232 00:09:44,530 --> 00:09:46,640 and development or study only. 233 233 00:09:46,640 --> 00:09:50,570 This experimental range contains about 268 million addresses 234 234 00:09:50,570 --> 00:09:52,940 that are reserved for future use. 235 235 00:09:52,940 --> 00:09:53,773 Over the years, 236 236 00:09:53,773 --> 00:09:54,920 there've been a few proposals 237 237 00:09:54,920 --> 00:09:58,030 to reallocate these class E addresses for general use 238 238 00:09:58,030 --> 00:09:59,810 because public IPv4 addresses 239 239 00:09:59,810 --> 00:10:01,300 were becoming more and more scarce 240 240 00:10:01,300 --> 00:10:04,140 in the class A, class B, and class C ranges 241 241 00:10:04,140 --> 00:10:06,190 as more and more devices started getting connected 242 242 00:10:06,190 --> 00:10:07,220 to the internet. 243 243 00:10:07,220 --> 00:10:09,130 That said, so far to date, 244 244 00:10:09,130 --> 00:10:10,310 these class E addresses 245 245 00:10:10,310 --> 00:10:13,070 still remain allocated for experimental use only, 246 246 00:10:13,070 --> 00:10:15,440 and most IP implementations within our networks 247 247 00:10:15,440 --> 00:10:19,950 will consider any IP in this range from 240.0.0.0 248 248 00:10:19,950 --> 00:10:24,000 all the way up to 255.255.255.255 249 249 00:10:24,000 --> 00:10:28,100 to be invalid as a source or destination within a datagram. 250 250 00:10:28,100 --> 00:10:28,933 And therefore, 251 251 00:10:28,933 --> 00:10:31,920 the datagram would be rejected by the destination system. 252 252 00:10:31,920 --> 00:10:34,510 So if you try to send something to a window server 253 253 00:10:34,510 --> 00:10:35,720 or a workstation, 254 254 00:10:35,720 --> 00:10:38,080 it's going to refuse to communicate with that device 255 255 00:10:38,080 --> 00:10:40,950 if you claim to be from a class E address. 256 256 00:10:40,950 --> 00:10:41,783 All right. 257 257 00:10:41,783 --> 00:10:43,770 So now that we've covered the five different classes 258 258 00:10:43,770 --> 00:10:45,250 of IPv4 addresses, 259 259 00:10:45,250 --> 00:10:47,920 let's talk a little more about subnet masks. 260 260 00:10:47,920 --> 00:10:48,753 Let's pretend that 261 261 00:10:48,753 --> 00:10:52,410 we have an IP address of 192.168.1.4 again, 262 262 00:10:52,410 --> 00:10:56,870 with a subnet mask of 255.255.255.0. 263 263 00:10:56,870 --> 00:10:59,540 This subnet mask is the default subnet mask 264 264 00:10:59,540 --> 00:11:00,890 for a class C network. 265 265 00:11:00,890 --> 00:11:03,590 And since our IP address begins with a 192, 266 266 00:11:03,590 --> 00:11:05,770 it is also a class C address. 267 267 00:11:05,770 --> 00:11:07,810 This means we have a class C address 268 268 00:11:07,810 --> 00:11:10,100 using a class C default subnet mask. 269 269 00:11:10,100 --> 00:11:13,120 So we consider this to be classful 270 270 00:11:13,120 --> 00:11:15,480 We call this a classful mask. 271 271 00:11:15,480 --> 00:11:18,500 Now, a classful subnet mask is just the default 272 272 00:11:18,500 --> 00:11:20,630 for a given class of IP address. 273 273 00:11:20,630 --> 00:11:21,740 This doesn't mean though, 274 274 00:11:21,740 --> 00:11:24,000 that it's the best one for us to always use. 275 275 00:11:24,000 --> 00:11:26,460 For example, if we're using a class A address, 276 276 00:11:26,460 --> 00:11:31,460 you may recall that his default subnet mask is 255.0.0.0. 277 277 00:11:31,800 --> 00:11:33,810 This means we have a possibility of having 278 278 00:11:33,810 --> 00:11:37,530 16.7 million hosts on a single network. 279 279 00:11:37,530 --> 00:11:38,780 Now, I don't know about you, 280 280 00:11:38,780 --> 00:11:41,420 but I don't often come across networks that are that large 281 281 00:11:41,420 --> 00:11:43,120 and require that many hosts. 282 282 00:11:43,120 --> 00:11:44,230 In fact, I used to work 283 283 00:11:44,230 --> 00:11:46,260 on one of the world's largest internets, 284 284 00:11:46,260 --> 00:11:48,610 and we had a little over 1 million hosts 285 285 00:11:48,610 --> 00:11:51,180 spread across six continents around the globe. 286 286 00:11:51,180 --> 00:11:53,320 That was a really, really big network, 287 287 00:11:53,320 --> 00:11:54,860 and we still didn't come close 288 288 00:11:54,860 --> 00:11:57,740 to using all 16.7 million IP addresses 289 289 00:11:57,740 --> 00:11:59,860 in a classful class A subnet. 290 290 00:11:59,860 --> 00:12:01,800 So, often what we'll want to do 291 291 00:12:01,800 --> 00:12:04,530 is break up these networks into smaller networks. 292 292 00:12:04,530 --> 00:12:07,500 So we often instead want to break down these large networks 293 293 00:12:07,500 --> 00:12:09,020 into smaller networks. 294 294 00:12:09,020 --> 00:12:09,853 To do this, 295 295 00:12:09,853 --> 00:12:11,900 we're going to use a process known as subnetting. 296 296 00:12:11,900 --> 00:12:13,990 Now, we're not going to cover subnetting in detail 297 297 00:12:13,990 --> 00:12:15,180 in this lesson. 298 298 00:12:15,180 --> 00:12:17,970 Instead, I'm going to dedicate a few lessons later on 299 299 00:12:17,970 --> 00:12:19,610 to fully dive into that concept 300 300 00:12:19,610 --> 00:12:21,630 because you need to understand how to do it. 301 301 00:12:21,630 --> 00:12:22,500 But for now, 302 302 00:12:22,500 --> 00:12:24,540 I just want you to remember that we don't have to stick 303 303 00:12:24,540 --> 00:12:26,350 with a classical subnet mask. 304 304 00:12:26,350 --> 00:12:30,040 Instead, we can use a classless subnet mask if we want to. 305 305 00:12:30,040 --> 00:12:33,620 This is a process known as classless inter-domain routing. 306 306 00:12:33,620 --> 00:12:35,930 This will let us borrow some of those host bits, 307 307 00:12:35,930 --> 00:12:37,860 those zeros that I showed you in the subnet mask, 308 308 00:12:37,860 --> 00:12:40,580 and then reassign them to the network portion. 309 309 00:12:40,580 --> 00:12:43,150 So this lets me cut down the size of my networks 310 310 00:12:43,150 --> 00:12:45,600 into much smaller portions with less hosts 311 311 00:12:45,600 --> 00:12:46,830 and this is more efficient. 312 312 00:12:46,830 --> 00:12:48,100 This will give me, at the same time, 313 313 00:12:48,100 --> 00:12:50,370 a lot more networks that I can possibly use. 314 314 00:12:50,370 --> 00:12:52,320 Because again, if you think of it like a pie, 315 315 00:12:52,320 --> 00:12:53,850 you can cut it many different ways, 316 316 00:12:53,850 --> 00:12:56,410 but it's still one pie and it's a fixed amount of IPs 317 317 00:12:56,410 --> 00:12:57,610 that we have in total. 318 318 00:12:57,610 --> 00:12:59,430 So, I can cut the pie in half 319 319 00:12:59,430 --> 00:13:01,200 and we'd have two halves of the pie, 320 320 00:13:01,200 --> 00:13:02,500 or I can cut it in quarters 321 321 00:13:02,500 --> 00:13:04,190 and we can have four pieces of pie, 322 322 00:13:04,190 --> 00:13:06,130 but each of those pieces are smaller. 323 323 00:13:06,130 --> 00:13:07,980 The same thing with our networks. 324 324 00:13:07,980 --> 00:13:09,260 So, for example, 325 325 00:13:09,260 --> 00:13:11,810 let's say I have a classful class C subnet mask, 326 326 00:13:11,810 --> 00:13:16,810 and I would have 255.255.255.0 as that subnet mask. 327 327 00:13:16,840 --> 00:13:19,710 This allowed me to have 256 hosts, right? 328 328 00:13:19,710 --> 00:13:20,880 Well, in my home network, 329 329 00:13:20,880 --> 00:13:23,310 I don't really need 256 hosts. 330 330 00:13:23,310 --> 00:13:26,630 So maybe I want to break this down into four smaller networks. 331 331 00:13:26,630 --> 00:13:29,390 If I take 256 and I divide it by four, 332 332 00:13:29,390 --> 00:13:32,740 I get 64 hosts for each of those four networks. 333 333 00:13:32,740 --> 00:13:33,573 To do this, 334 334 00:13:33,573 --> 00:13:38,030 I would change the subnet mask from 255.255.255.0 335 335 00:13:38,030 --> 00:13:42,010 to 255.255.255.192. 336 336 00:13:42,010 --> 00:13:43,040 How do I do this? 337 337 00:13:43,040 --> 00:13:45,130 Well, I borrowed two bits from the host 338 338 00:13:45,130 --> 00:13:47,730 and I gave it to the network portion of the address. 339 339 00:13:47,730 --> 00:13:50,420 And this is how I make four different subnetworks 340 340 00:13:50,420 --> 00:13:53,740 or subnets out of this by using my subnet mask. 341 341 00:13:53,740 --> 00:13:54,930 Now, later on in this section, 342 342 00:13:54,930 --> 00:13:56,740 I'm going to teach you how to do subnetting 343 343 00:13:56,740 --> 00:13:59,800 and understand how I got that number for that subnet mask, 344 344 00:13:59,800 --> 00:14:01,490 including all the math involved, 345 345 00:14:01,490 --> 00:14:02,750 just like I did here. 346 346 00:14:02,750 --> 00:14:03,930 But for now, 347 347 00:14:03,930 --> 00:14:06,080 I just want you to remember that subnetting allows you 348 348 00:14:06,080 --> 00:14:09,130 to use a classless subnet mask to create smaller networks 349 349 00:14:09,130 --> 00:14:11,780 with fewer hosts in each of those networks than you could 350 350 00:14:11,780 --> 00:14:14,440 if you had a classful subnet mask by itself. 351 351 00:14:14,440 --> 00:14:15,747 This process is known as 352 352 00:14:15,747 --> 00:14:19,170 the classless inter-domain routing or CIDR, 353 353 00:14:19,170 --> 00:14:21,340 and we are going to abbreviate our IP addresses 354 354 00:14:21,340 --> 00:14:24,650 using this CIDR or CIDR notation. 355 355 00:14:24,650 --> 00:14:25,750 Now, when we do this, 356 356 00:14:25,750 --> 00:14:27,600 we don't have to write out the subnet mask. 357 357 00:14:27,600 --> 00:14:31,650 Instead, we just write the IP address, a slash and a number. 358 358 00:14:31,650 --> 00:14:33,910 This is known as our CIDR notation. 359 359 00:14:33,910 --> 00:14:38,690 So if I have an IP address of 192.168.1.4 360 360 00:14:38,690 --> 00:14:42,890 with a subnet mask of 255.255.255.0, 361 361 00:14:42,890 --> 00:14:47,760 I can abbreviate this using CIDR notation as 192.168.1.4/24. 362 362 00:14:50,220 --> 00:14:53,930 Oftentimes, you'll hear this called CIDR or slash notation. 363 363 00:14:53,930 --> 00:14:57,920 Now, if I had an IP address of 192.168.1.4, 364 364 00:14:57,920 --> 00:15:02,920 but my subnet mask was 255.255.255.192, 365 365 00:15:03,000 --> 00:15:08,000 I can abbreviate that as 192.168.1.4/26 366 366 00:15:09,100 --> 00:15:12,400 because remember, I borrowed two bits from the host portion. 367 367 00:15:12,400 --> 00:15:16,440 So I went from 24 as my default subnet mask, /24, 368 368 00:15:16,440 --> 00:15:17,800 into a /26, 369 369 00:15:17,800 --> 00:15:20,830 by borrowing two bits and making my network portion 370 370 00:15:20,830 --> 00:15:22,090 that much larger, 371 371 00:15:22,090 --> 00:15:24,810 bringing it from 24 up to 26. 372 372 00:15:24,810 --> 00:15:27,520 Now, when you're trying to calculate your CIDR notation, 373 373 00:15:27,520 --> 00:15:28,890 it's really going to be easiest 374 374 00:15:28,890 --> 00:15:31,100 when you're dealing with classful subnet masks. 375 375 00:15:31,100 --> 00:15:33,770 The CIDR notation here is really, really easy. 376 376 00:15:33,770 --> 00:15:35,710 Now, for the classful subnet masks, 377 377 00:15:35,710 --> 00:15:38,480 our CIDR notation is going to be rather simple. 378 378 00:15:38,480 --> 00:15:41,110 If you have a class A classful subnet mask, 379 379 00:15:41,110 --> 00:15:44,130 you're going to have a /8 after the IP address. 380 380 00:15:44,130 --> 00:15:48,050 This means that the subnet mask is 255.0.0.0, 381 381 00:15:48,050 --> 00:15:50,210 or it has eight bits of ones, 382 382 00:15:50,210 --> 00:15:51,240 which is the /8, 383 383 00:15:51,240 --> 00:15:54,950 and then 24 bits of zeros inside the subnet mask. 384 384 00:15:54,950 --> 00:15:57,320 Now, if you have a class B classful subnet mask, 385 385 00:15:57,320 --> 00:16:00,510 you're going to use a /16 after your IP address. 386 386 00:16:00,510 --> 00:16:04,800 This means the subnet mask is 255.255.0.0. 387 387 00:16:04,800 --> 00:16:07,310 Also, it means that it has 16 bits of ones 388 388 00:16:07,310 --> 00:16:10,600 and 16 bits of zeros in that subnet mask. 389 389 00:16:10,600 --> 00:16:12,970 Now, if you have a class C class will subnet mask, 390 390 00:16:12,970 --> 00:16:16,260 you're going to use a /24 after the IP address. 391 391 00:16:16,260 --> 00:16:21,020 This means that the subnet mask is going to be 255.255.255.0, 392 392 00:16:21,020 --> 00:16:23,690 or that it has 24 bits of ones 393 393 00:16:23,690 --> 00:16:26,850 and then eight bits of zeros in that subnet mask. 394 394 00:16:26,850 --> 00:16:28,240 Next, we need to talk about 395 395 00:16:28,240 --> 00:16:30,750 two different types of IPv4 addresses. 396 396 00:16:30,750 --> 00:16:32,970 These are called public and private IPs, 397 397 00:16:32,970 --> 00:16:35,120 and you may also hear them called routable 398 398 00:16:35,120 --> 00:16:36,950 and non-routable IPs. 399 399 00:16:36,950 --> 00:16:39,830 When an IP is considered a public or a routable IP, 400 400 00:16:39,830 --> 00:16:43,030 this IP address can be directly accessed over the internet 401 401 00:16:43,030 --> 00:16:44,410 and assigned to your network 402 402 00:16:44,410 --> 00:16:46,470 by your internet service provider. 403 403 00:16:46,470 --> 00:16:48,600 Routable IPs are publicly routable 404 404 00:16:48,600 --> 00:16:50,030 across the entire internet, 405 405 00:16:50,030 --> 00:16:53,040 and therefore, they're globally managed by ICANN. 406 406 00:16:53,040 --> 00:16:54,810 ICANN is the Internet Corporation 407 407 00:16:54,810 --> 00:16:56,570 for Assigned Names and Numbers. 408 408 00:16:56,570 --> 00:16:58,710 So if you want a public IP address, 409 409 00:16:58,710 --> 00:17:00,760 like for running a web server for your company 410 410 00:17:00,760 --> 00:17:02,570 or a Minecraft server for your kids, 411 411 00:17:02,570 --> 00:17:04,090 you can buy that IP address 412 412 00:17:04,090 --> 00:17:06,900 and ICANN is the one who will lease those out to you. 413 413 00:17:06,900 --> 00:17:09,630 Now, ICANN has five different groups underneath them 414 414 00:17:09,630 --> 00:17:10,610 who are responsible for actually 415 415 00:17:10,610 --> 00:17:12,350 handing out these public IPs 416 416 00:17:12,350 --> 00:17:14,470 based on where you actually live in the world. 417 417 00:17:14,470 --> 00:17:17,650 There is ARAIN, A-R-I-N, which is for North America. 418 418 00:17:17,650 --> 00:17:21,130 There's LACNIC, L-A-C-N-I-C, which is for Latin America. 419 419 00:17:21,130 --> 00:17:24,450 There's ethnic AFNIC, A-F-N-I-C, which is for Africa. 420 420 00:17:24,450 --> 00:17:26,630 There's APNIC, A-P-N-I-C, 421 421 00:17:26,630 --> 00:17:28,400 which is for Asia and the Pacific region. 422 422 00:17:28,400 --> 00:17:31,640 And there's RIPE, R-I-P-E, which is for Europe. 423 423 00:17:31,640 --> 00:17:33,850 These are the ones who are responsible for the management 424 424 00:17:33,850 --> 00:17:36,550 of the public IP space on behalf of ICANN 425 425 00:17:36,550 --> 00:17:38,450 in each of those different regions. 426 426 00:17:38,450 --> 00:17:40,110 Now, since I'm located in America, 427 427 00:17:40,110 --> 00:17:41,840 if I wanted a public IP address, 428 428 00:17:41,840 --> 00:17:43,490 I should go to ARIN, right? 429 429 00:17:43,490 --> 00:17:45,620 Well, not exactly. 430 430 00:17:45,620 --> 00:17:47,610 ARIN will be way too busy to handle that. 431 431 00:17:47,610 --> 00:17:49,920 They're not just going to sell me one address, 432 432 00:17:49,920 --> 00:17:51,120 they're only going to sell me IPs 433 433 00:17:51,120 --> 00:17:53,250 if I want a whole bunch of IPs. 434 434 00:17:53,250 --> 00:17:55,740 So instead, I'm going to have to go to a reseller 435 435 00:17:55,740 --> 00:17:57,860 who will sell me just a single IP. 436 436 00:17:57,860 --> 00:18:00,810 In my case, I can contact my internet service provider, 437 437 00:18:00,810 --> 00:18:02,550 somebody like Verizon or Comcast 438 438 00:18:02,550 --> 00:18:04,740 and tell them that I want a public IP. 439 439 00:18:04,740 --> 00:18:06,900 Then Verizon will pick me out one 440 440 00:18:06,900 --> 00:18:09,150 out of their entire chunk from ARIN that they have 441 441 00:18:09,150 --> 00:18:11,950 such as a class A with 16.7 million IPs, 442 442 00:18:11,950 --> 00:18:16,830 or a class B with 65,536 IPs and assign one to me. 443 443 00:18:16,830 --> 00:18:19,650 This way, Verizon can lease out that single IP 444 444 00:18:19,650 --> 00:18:22,300 or a small subnet worth of IPs for my company 445 445 00:18:22,300 --> 00:18:24,180 'cause maybe I need 5 or 10 of them. 446 446 00:18:24,180 --> 00:18:26,980 Public IPs must be purchased before you can use them 447 447 00:18:26,980 --> 00:18:27,813 and you do this 448 448 00:18:27,813 --> 00:18:29,950 through your local internet service provider. 449 449 00:18:29,950 --> 00:18:30,860 Now, on the other hand, 450 450 00:18:30,860 --> 00:18:33,830 there are also non-routable IPs known as private IPs, 451 451 00:18:33,830 --> 00:18:36,150 because, well, they're not public. 452 452 00:18:36,150 --> 00:18:39,120 Private IPs can be used by anyone at any time, 453 453 00:18:39,120 --> 00:18:41,800 but only within their own local area networks. 454 454 00:18:41,800 --> 00:18:44,630 This is why these IPs are considered not routable 455 455 00:18:44,630 --> 00:18:46,670 because no one is controlling who's using them 456 456 00:18:46,670 --> 00:18:48,310 and in which networks. 457 457 00:18:48,310 --> 00:18:49,143 In fact, 458 458 00:18:49,143 --> 00:18:51,490 if you look at your IP address of your computer right now, 459 459 00:18:51,490 --> 00:18:52,547 I bet you're using an IP address 460 460 00:18:52,547 --> 00:18:56,520 and it starts with either a 10, a 172, or a 192 461 461 00:18:56,520 --> 00:18:57,980 as its first octet. 462 462 00:18:57,980 --> 00:18:58,870 Don't believe me? 463 463 00:18:58,870 --> 00:19:01,240 Go ahead, pause this video and check. 464 464 00:19:01,240 --> 00:19:02,140 If you don't know how to check, 465 465 00:19:02,140 --> 00:19:04,090 I'm going to tell you how to do it right now. 466 466 00:19:04,090 --> 00:19:05,500 If you're on a Windows computer, 467 467 00:19:05,500 --> 00:19:07,170 I want you to hold down the Windows key 468 468 00:19:07,170 --> 00:19:09,230 and press the R key at the same time. 469 469 00:19:09,230 --> 00:19:12,210 Then type CMD and hit enter. 470 470 00:19:12,210 --> 00:19:13,710 This stands for command. 471 471 00:19:13,710 --> 00:19:15,920 Next, you have this black window on your screen. 472 472 00:19:15,920 --> 00:19:19,540 Type in ipconfig for IP configuration, 473 473 00:19:19,540 --> 00:19:22,220 and then hit enter and look at your IP address. 474 474 00:19:22,220 --> 00:19:25,380 Does it start with a 10, a 172 or a 192? 475 475 00:19:25,380 --> 00:19:26,700 I bet it does. 476 476 00:19:26,700 --> 00:19:28,050 Now, if you're on a Mac, don't worry. 477 477 00:19:28,050 --> 00:19:29,260 I'm not leaving you out. 478 478 00:19:29,260 --> 00:19:31,200 You can go ahead and look at this as well. 479 479 00:19:31,200 --> 00:19:32,160 If you're watching this video 480 480 00:19:32,160 --> 00:19:33,880 over a wireless network connection, 481 481 00:19:33,880 --> 00:19:35,830 go ahead and hold down your option key 482 482 00:19:35,830 --> 00:19:37,660 and then click on the Wi-Fi icon 483 483 00:19:37,660 --> 00:19:39,410 in the top right of your menu bar. 484 484 00:19:39,410 --> 00:19:41,410 Look down under your wireless networks name, 485 485 00:19:41,410 --> 00:19:42,990 and you're going to see your IP address. 486 486 00:19:42,990 --> 00:19:45,570 Again, I bet it starts today with either a 10, 487 487 00:19:45,570 --> 00:19:49,330 a 172 or a 192 as part of that IP. 488 488 00:19:49,330 --> 00:19:50,410 Now, am I a magician 489 489 00:19:50,410 --> 00:19:52,480 being able to tell you what your IP address is? 490 490 00:19:52,480 --> 00:19:53,730 Well, not really. 491 491 00:19:53,730 --> 00:19:55,110 You see those three values 492 492 00:19:55,110 --> 00:19:57,880 are part of what we call the private IP ranges. 493 493 00:19:57,880 --> 00:20:01,140 This includes something like 10.0.0.something, 494 494 00:20:01,140 --> 00:20:04,350 or 172.16.1.something, 495 495 00:20:04,350 --> 00:20:07,450 or 192.168.1.something 496 496 00:20:07,450 --> 00:20:09,440 and a bunch of other IPs as well. 497 497 00:20:09,440 --> 00:20:11,650 So, if you're using one of these private IPs, 498 498 00:20:11,650 --> 00:20:13,220 and I said they're not routable, 499 499 00:20:13,220 --> 00:20:14,620 how are you actually getting out to the internet 500 500 00:20:14,620 --> 00:20:16,170 to watch this video? 501 501 00:20:16,170 --> 00:20:18,000 Well, when you go out to the internet, 502 502 00:20:18,000 --> 00:20:20,200 your router actually conducts a little trick 503 503 00:20:20,200 --> 00:20:21,940 known as Network Address Translation, 504 504 00:20:21,940 --> 00:20:25,270 and it changes your private IP into a public IP. 505 505 00:20:25,270 --> 00:20:26,720 Now, we're going to cover the concept 506 506 00:20:26,720 --> 00:20:28,090 of Network Address Translation 507 507 00:20:28,090 --> 00:20:30,550 and Port Address Translation in a separate lesson 508 508 00:20:30,550 --> 00:20:32,340 because it's really important for you understand that. 509 509 00:20:32,340 --> 00:20:33,173 But for now, 510 510 00:20:33,173 --> 00:20:36,110 let's stick to talking about these private IPs. 511 511 00:20:36,110 --> 00:20:36,943 All right. 512 512 00:20:36,943 --> 00:20:37,776 For the exam 513 513 00:20:37,776 --> 00:20:39,950 and your life as a real world network technician, 514 514 00:20:39,950 --> 00:20:41,900 it's going to be really important for you to understand 515 515 00:20:41,900 --> 00:20:44,320 the ranges for private IP addresses. 516 516 00:20:44,320 --> 00:20:48,203 Now, these are defined in something known as RFC 1918. 517 517 00:20:48,203 --> 00:20:50,890 Now, RFC just stands for request for comments. 518 518 00:20:50,890 --> 00:20:53,270 And request for comments is a formal publication 519 519 00:20:53,270 --> 00:20:54,500 from the Internet Society 520 520 00:20:54,500 --> 00:20:57,890 and the Internet Engineering Task Force or IETF. 521 521 00:20:57,890 --> 00:21:00,070 These RFCs are authored by individuals 522 522 00:21:00,070 --> 00:21:01,680 or groups of computer scientists 523 523 00:21:01,680 --> 00:21:04,180 to document new technologies or standards. 524 524 00:21:04,180 --> 00:21:07,280 In this case, the RFC 1918, 525 525 00:21:07,280 --> 00:21:09,520 this is going to be used to document how organizations 526 526 00:21:09,520 --> 00:21:12,660 can conduct address allocation for private internet, 527 527 00:21:12,660 --> 00:21:16,180 which we now call intranet or your local area networks. 528 528 00:21:16,180 --> 00:21:18,130 Now in RFC 1918, 529 529 00:21:18,130 --> 00:21:20,910 there are specific ranges of private IPs described 530 530 00:21:20,910 --> 00:21:24,530 within class A, B and C that anyone can use. 531 531 00:21:24,530 --> 00:21:26,520 If you're looking at class A addresses, 532 532 00:21:26,520 --> 00:21:29,060 anything that starts with a 10 in the first octet 533 533 00:21:29,060 --> 00:21:31,230 is going to be considered a private IP. 534 534 00:21:31,230 --> 00:21:34,640 So, you can have anything from 10.0.0.0 535 535 00:21:34,640 --> 00:21:39,330 all the way up to 10.255.255.255 as your address, 536 536 00:21:39,330 --> 00:21:40,920 and it's going to be a private IP. 537 537 00:21:40,920 --> 00:21:44,730 This gives you a total of 16.7 million IP addresses 538 538 00:21:44,730 --> 00:21:46,280 that anyone can use. 539 539 00:21:46,280 --> 00:21:47,400 Now, in addition to that, 540 540 00:21:47,400 --> 00:21:49,170 we also have some class B addresses, 541 541 00:21:49,170 --> 00:21:51,270 and this one's a little bit harder to memorize. 542 542 00:21:51,270 --> 00:21:52,560 For class B addresses, 543 543 00:21:52,560 --> 00:21:55,490 anything that starts with a 172.16 544 544 00:21:55,490 --> 00:21:57,930 all the way up to 172.31 545 545 00:21:57,930 --> 00:22:00,450 is going to be part of a private IP range. 546 546 00:22:00,450 --> 00:22:03,150 This includes over 1 million IP addresses 547 547 00:22:03,150 --> 00:22:07,120 because we have 16 times 256 times 256. 548 548 00:22:07,120 --> 00:22:09,340 Now, if you're looking at a class C address, 549 549 00:22:09,340 --> 00:22:12,090 anything that starts with a 192.168 550 550 00:22:12,090 --> 00:22:14,010 is considered a private IP. 551 551 00:22:14,010 --> 00:22:17,810 This includes a range of 192.168.0.0 552 552 00:22:17,810 --> 00:22:22,070 all the way up to 192.168.255.255. 553 553 00:22:22,070 --> 00:22:25,990 This gives you 65,536 IP addresses 554 554 00:22:25,990 --> 00:22:28,400 that are there for you to use if you want them. 555 555 00:22:28,400 --> 00:22:30,740 Now, I want you to commit these ranges to memory. 556 556 00:22:30,740 --> 00:22:32,930 Remember, class A is really easy. 557 557 00:22:32,930 --> 00:22:34,450 Anything that starts with a 10 558 558 00:22:34,450 --> 00:22:36,100 dot something dot something dot something 559 559 00:22:36,100 --> 00:22:38,470 is a private IP in the class A range. 560 560 00:22:38,470 --> 00:22:40,090 Now, class C is also pretty easy 561 561 00:22:40,090 --> 00:22:43,850 because anything that is 192.168 dot something dot something 562 562 00:22:43,850 --> 00:22:46,460 is also considered a private address, in this case, 563 563 00:22:46,460 --> 00:22:48,290 a class C private address. 564 564 00:22:48,290 --> 00:22:50,850 But class B is where most people are going to struggle 565 565 00:22:50,850 --> 00:22:52,420 because it's a little bit different. 566 566 00:22:52,420 --> 00:22:54,140 It's going to contain any addresses 567 567 00:22:54,140 --> 00:22:57,700 that start with 172.16 dot something dot something 568 568 00:22:57,700 --> 00:23:01,440 all the way up to 172.31 dot something dot something. 569 569 00:23:01,440 --> 00:23:04,780 This is essentially 16 classes of class B addresses 570 570 00:23:04,780 --> 00:23:06,220 that are all next to each other, 571 571 00:23:06,220 --> 00:23:09,000 and you could use any of them as a private IP. 572 572 00:23:09,000 --> 00:23:10,280 Now, on test day, 573 573 00:23:10,280 --> 00:23:13,120 CompTIA may try to trick you and say something like, 574 574 00:23:13,120 --> 00:23:15,750 which of these addresses is not a private IP? 575 575 00:23:15,750 --> 00:23:17,410 And then they're going to give you something like 576 576 00:23:17,410 --> 00:23:19,950 172.12 dot something dot something. 577 577 00:23:19,950 --> 00:23:21,570 Now, this starts with a 172, 578 578 00:23:21,570 --> 00:23:23,300 so it looks like a private IP, 579 579 00:23:23,300 --> 00:23:26,120 but because it's 172.12, 580 580 00:23:26,120 --> 00:23:30,570 it's not between 172.16 and 172.31. 581 581 00:23:30,570 --> 00:23:33,590 So 172.12 dot something dot something 582 582 00:23:33,590 --> 00:23:35,410 is actually a private IP 583 583 00:23:35,410 --> 00:23:37,590 because it's outside of my private range. 584 584 00:23:37,590 --> 00:23:38,950 You have to be especially careful 585 585 00:23:38,950 --> 00:23:41,160 when you see an address that starts with 172 586 586 00:23:41,160 --> 00:23:45,423 because it has to be between 172.16 to 172.31 587 587 00:23:46,600 --> 00:23:48,350 to be a private IP. 588 588 00:23:48,350 --> 00:23:51,040 All of the other 172 dot something addresses 589 589 00:23:51,040 --> 00:23:52,530 will be public. 590 590 00:23:52,530 --> 00:23:54,190 Now, the next thing we need to talk about 591 591 00:23:54,190 --> 00:23:55,950 is some specialized IPS, 592 592 00:23:55,950 --> 00:23:58,340 and there are two big categories that we need to cover: 593 593 00:23:58,340 --> 00:24:01,180 the loopback address and APIPA addresses. 594 594 00:24:01,180 --> 00:24:04,080 Now, the first special IP is the loopback address. 595 595 00:24:04,080 --> 00:24:07,580 This is assigned as 127.0.0.1. 596 596 00:24:07,580 --> 00:24:08,500 Now, when this was created 597 597 00:24:08,500 --> 00:24:10,550 all the way back in the early days of the internet, 598 598 00:24:10,550 --> 00:24:13,060 the designers weren't too worried about wasting IPs 599 599 00:24:13,060 --> 00:24:14,100 because they never envisioned 600 600 00:24:14,100 --> 00:24:16,160 that we were going to use a lot of IP addresses 601 601 00:24:16,160 --> 00:24:17,390 in the entire world. 602 602 00:24:17,390 --> 00:24:22,390 So they simply dedicate an entire range that's 127.0.0.1/8 603 603 00:24:23,630 --> 00:24:26,540 or 16.7 million IP addresses 604 604 00:24:26,540 --> 00:24:29,270 to be used as internet hosts loopback addresses. 605 605 00:24:29,270 --> 00:24:31,550 Now, this allows any higher level protocol 606 606 00:24:31,550 --> 00:24:33,520 to send data to the host itself 607 607 00:24:33,520 --> 00:24:36,050 without actually going out to a switch or a router. 608 608 00:24:36,050 --> 00:24:38,320 Essentially, this creates a loop back to the host 609 609 00:24:38,320 --> 00:24:40,250 and it tests your networking protocols. 610 610 00:24:40,250 --> 00:24:41,740 So it's often used in troubleshooting 611 611 00:24:41,740 --> 00:24:44,210 and testing that were protocols on a given system 612 612 00:24:44,210 --> 00:24:46,390 to make sure your drivers are working properly. 613 613 00:24:46,390 --> 00:24:48,450 Now, because of the way the standard was developed, 614 614 00:24:48,450 --> 00:24:49,283 anything you see 615 615 00:24:49,283 --> 00:24:51,124 that starts with 127 dot something dot something 616 616 00:24:51,124 --> 00:24:54,140 dot something is considered a loopback address, 617 617 00:24:54,140 --> 00:24:58,430 although most people just use 127.0.0.1 618 618 00:24:58,430 --> 00:25:00,580 as our loopback address by default. 619 619 00:25:00,580 --> 00:25:04,650 This means the other 16.7 million IPs are pretty much wasted 620 620 00:25:04,650 --> 00:25:06,130 because we're using this range 621 621 00:25:06,130 --> 00:25:07,720 to be the entire loopback range, 622 622 00:25:07,720 --> 00:25:10,830 even though most of us only use this one IP address. 623 623 00:25:10,830 --> 00:25:12,310 Now, you may have heard the old joke 624 624 00:25:12,310 --> 00:25:14,210 that some network technicians like to use. 625 625 00:25:14,210 --> 00:25:17,490 There's no place like 127.0.0.1, 626 626 00:25:17,490 --> 00:25:20,270 which means there's no place like here, home, right? 627 627 00:25:20,270 --> 00:25:22,130 That's one 127.0.0.1. 628 628 00:25:22,130 --> 00:25:23,450 It's the local host. 629 629 00:25:23,450 --> 00:25:24,910 Now, and during the COVID pandemic, 630 630 00:25:24,910 --> 00:25:29,410 I also saw a couple of funny memes saying stay at 127.0.0.1 631 631 00:25:29,410 --> 00:25:33,110 and wear a 255.255.255.0, 632 632 00:25:33,110 --> 00:25:34,270 which essentially says, 633 633 00:25:34,270 --> 00:25:36,170 stay at home and wear a mask. 634 634 00:25:36,170 --> 00:25:40,130 Now, when it comes to the IP address of 127.0.0.1, 635 635 00:25:40,130 --> 00:25:41,960 you're going to hear it called either the loopback 636 636 00:25:41,960 --> 00:25:44,340 or you might hear people call it the local host, 637 637 00:25:44,340 --> 00:25:45,630 like I did earlier. 638 638 00:25:45,630 --> 00:25:50,090 Now, the word local hosts will always resolve to 127.0.0.1 639 639 00:25:50,090 --> 00:25:53,000 on every computer as part of its local DNS settings. 640 640 00:25:53,000 --> 00:25:58,000 So if you ping 127.0.0.1 or you ping local hosts, 641 641 00:25:58,140 --> 00:25:59,770 you're going to get the same result. 642 642 00:25:59,770 --> 00:26:01,460 It's going to result to the IP address 643 643 00:26:01,460 --> 00:26:05,650 of that loopback IP, 127.0.0.1. 644 644 00:26:05,650 --> 00:26:07,870 Now, the second special IP addresses we have 645 645 00:26:07,870 --> 00:26:10,940 is known as APIPA, A-P-I-P-A. 646 646 00:26:10,940 --> 00:26:14,190 This is also known as the Automatic Private IP Addresses. 647 647 00:26:14,190 --> 00:26:15,910 These addresses are dynamically assigned 648 648 00:26:15,910 --> 00:26:17,100 by your operating system 649 649 00:26:17,100 --> 00:26:19,370 whenever your DHCP server is unavailable 650 650 00:26:19,370 --> 00:26:22,853 and an IP address has not already been statically assigned. 651 651 00:26:22,853 --> 00:26:24,337 APIPA addresses are always going to start with 652 652 00:26:24,337 --> 00:26:28,060 169.254 dot something dot something. 653 653 00:26:28,060 --> 00:26:29,220 So you're going to find them 654 654 00:26:29,220 --> 00:26:33,360 in the address range of 169.254.0.0 655 655 00:26:33,360 --> 00:26:37,800 all the way up to 169.254.255.255. 656 656 00:26:37,800 --> 00:26:40,320 So if you ever see an IP address in this range 657 657 00:26:40,320 --> 00:26:42,400 when you look at the IP of a network device, 658 658 00:26:42,400 --> 00:26:45,000 it means that there is something wrong with the DHCP process 659 659 00:26:45,000 --> 00:26:47,520 and the device isn't getting a normal private IP 660 660 00:26:47,520 --> 00:26:50,980 from one of our class A, class B or class C ranges. 661 661 00:26:50,980 --> 00:26:52,710 Now, as your workstation boots up, 662 662 00:26:52,710 --> 00:26:54,790 it's going to attempt to get its own IP address 663 663 00:26:54,790 --> 00:26:58,290 using dynamic IPS using the DHCP protocol. 664 664 00:26:58,290 --> 00:27:01,370 This goes through a four-step process known as DORA. 665 665 00:27:01,370 --> 00:27:04,890 This is discover, offer, request and acknowledge. 666 666 00:27:04,890 --> 00:27:05,810 If something goes wrong 667 667 00:27:05,810 --> 00:27:08,670 with this DORA negotiation process with DHCP, 668 668 00:27:08,670 --> 00:27:10,730 the system simply can't get an address 669 669 00:27:10,730 --> 00:27:12,370 and your computer would eventually just crash 670 670 00:27:12,370 --> 00:27:13,800 because it wouldn't know what to do, 671 671 00:27:13,800 --> 00:27:15,830 and it would keep trying over and over again. 672 672 00:27:15,830 --> 00:27:17,360 So with the brilliant engineers 673 673 00:27:17,360 --> 00:27:20,550 of the Internet Task Force did was create this APIPA range. 674 674 00:27:20,550 --> 00:27:22,000 Now, basically what it says is that 675 675 00:27:22,000 --> 00:27:24,110 if a workstation can't get a DHCP assignment 676 676 00:27:24,110 --> 00:27:26,990 for a dynamic IP address within some amount of time, 677 677 00:27:26,990 --> 00:27:29,210 the workstation is simply going to pick its own address 678 678 00:27:29,210 --> 00:27:30,990 from this special APIPA range. 679 679 00:27:30,990 --> 00:27:32,530 Basically, any IP at once, 680 680 00:27:32,530 --> 00:27:33,930 as long as it starts with 681 681 00:27:33,930 --> 00:27:36,990 169.254 dot something dot something. 682 682 00:27:36,990 --> 00:27:38,470 So if you find a computer 683 683 00:27:38,470 --> 00:27:40,040 that can not connect to the internet, 684 684 00:27:40,040 --> 00:27:42,810 the first thing you should do is check its IP address. 685 685 00:27:42,810 --> 00:27:44,990 You can do this using ipconfig on Windows, 686 686 00:27:44,990 --> 00:27:47,840 or ifconfig on Mac or Linux machines. 687 687 00:27:47,840 --> 00:27:49,340 Now, if you see an IP address of 688 688 00:27:49,340 --> 00:27:52,430 169.254 dot something dot something, 689 689 00:27:52,430 --> 00:27:54,480 you know you have a DHCP problem 690 690 00:27:54,480 --> 00:27:56,360 and you need to check your DHCP server 691 691 00:27:56,360 --> 00:27:57,770 to ensure it's working properly, 692 692 00:27:57,770 --> 00:27:59,770 and that it's handing out private IP addresses 693 693 00:27:59,770 --> 00:28:03,140 from class A, class B or class C assigned ranges. 694 694 00:28:03,140 --> 00:28:06,730 Now, that's as deep as we need to go into DHCP right now, 695 695 00:28:06,730 --> 00:28:09,870 but I promise we are going to go back to DHCP later on, 696 696 00:28:09,870 --> 00:28:11,430 and we'll talk about all of these things 697 697 00:28:11,430 --> 00:28:13,460 and how it provides these IP addresses 698 698 00:28:13,460 --> 00:28:16,290 and how those are going to be used inside your networks. 699 699 00:28:16,290 --> 00:28:18,100 Now, the last two things we need to discuss 700 700 00:28:18,100 --> 00:28:19,810 in terms of IPv4 addressing 701 701 00:28:19,810 --> 00:28:23,270 is the concept of virtual IP addresses and subinterfaces. 702 702 00:28:23,270 --> 00:28:26,010 Now, first let's talk about virtual IP addresses, 703 703 00:28:26,010 --> 00:28:29,320 usually abbreviate as VIP or VIPA. 704 704 00:28:29,320 --> 00:28:31,710 Now, a virtual IP address is an IP address 705 705 00:28:31,710 --> 00:28:32,880 that does not correlate 706 706 00:28:32,880 --> 00:28:35,250 to an actual physical network interface. 707 707 00:28:35,250 --> 00:28:37,270 Instead, these virtual IP addresses 708 708 00:28:37,270 --> 00:28:39,530 are usually used for network address translation, 709 709 00:28:39,530 --> 00:28:41,880 fault-tolerance and virtualization. 710 710 00:28:41,880 --> 00:28:42,713 In your computer, 711 711 00:28:42,713 --> 00:28:44,410 you have a network interface card, 712 712 00:28:44,410 --> 00:28:46,070 and normally you can only configure 713 713 00:28:46,070 --> 00:28:49,030 that network interface card with a single IP address 714 714 00:28:49,030 --> 00:28:51,480 because there's only one physical network interface, 715 715 00:28:51,480 --> 00:28:54,170 namely this network interface card. 716 716 00:28:54,170 --> 00:28:56,150 Now, with a virtual IP address, 717 717 00:28:56,150 --> 00:28:58,610 you can actually configure that network interface card 718 718 00:28:58,610 --> 00:29:00,500 to respond to numerous IP addresses 719 719 00:29:00,500 --> 00:29:01,610 and have them all resolved 720 720 00:29:01,610 --> 00:29:03,500 back to your physical network interface 721 721 00:29:03,500 --> 00:29:05,330 to establish the connectivity. 722 722 00:29:05,330 --> 00:29:07,770 Routers will often use virtual IP addresses 723 723 00:29:07,770 --> 00:29:10,640 to provide redundancy in their connectivity options as well. 724 724 00:29:10,640 --> 00:29:12,060 By having a single virtual IP 725 725 00:29:12,060 --> 00:29:14,110 assigned to the default gateway, for example, 726 726 00:29:14,110 --> 00:29:15,560 we can have multiple routers 727 727 00:29:15,560 --> 00:29:18,260 that can answer up on behalf of that virtual IP. 728 728 00:29:18,260 --> 00:29:19,900 This would allow us to have a primary device 729 729 00:29:19,900 --> 00:29:21,250 to use during normal conditions 730 730 00:29:21,250 --> 00:29:22,960 and alternate device that can be used 731 731 00:29:22,960 --> 00:29:24,420 when the primary device fails, 732 732 00:29:24,420 --> 00:29:27,220 so we could fail over to that secondary device. 733 733 00:29:27,220 --> 00:29:28,750 We'll talk more about this concept 734 734 00:29:28,750 --> 00:29:30,270 when we start digging into routers 735 735 00:29:30,270 --> 00:29:32,060 and covering concepts like redundancy. 736 736 00:29:32,060 --> 00:29:32,930 But for right now, 737 737 00:29:32,930 --> 00:29:34,540 I just wanted to introduce you to the concept 738 738 00:29:34,540 --> 00:29:36,480 that virtual IP addresses exist 739 739 00:29:36,480 --> 00:29:38,400 and we use them for things like redundancy 740 740 00:29:38,400 --> 00:29:40,820 and giving an interface, one physical interface, 741 741 00:29:40,820 --> 00:29:42,810 multiple different IP addresses. 742 742 00:29:42,810 --> 00:29:44,840 Now, the second concept we need to cover here 743 743 00:29:44,840 --> 00:29:46,670 is the idea of subinterfaces, 744 744 00:29:46,670 --> 00:29:48,170 which is a virtual interface 745 745 00:29:48,170 --> 00:29:50,360 that's created by dividing up one physical interface 746 746 00:29:50,360 --> 00:29:52,660 into multiple logical interfaces. 747 747 00:29:52,660 --> 00:29:53,800 This goes hand-in-hand 748 748 00:29:53,800 --> 00:29:55,740 with the concept of a virtual IP address 749 749 00:29:55,740 --> 00:29:57,550 because each of these virtual interfaces 750 750 00:29:57,550 --> 00:29:59,200 that we're going to create is going to be able 751 751 00:29:59,200 --> 00:30:01,670 to be assigned a virtual IP address as well. 752 752 00:30:01,670 --> 00:30:03,510 These subinterfaces are often used 753 753 00:30:03,510 --> 00:30:05,600 for inter-VLAN routing of traffic 754 754 00:30:05,600 --> 00:30:08,520 by creating two subinterfaces for one physical interface, 755 755 00:30:08,520 --> 00:30:10,770 and then assigning each of those subinterfaces 756 756 00:30:10,770 --> 00:30:13,520 with an IP address from the appropriate subnet. 757 757 00:30:13,520 --> 00:30:16,051 This then allows the rider to connect these two subnets 758 758 00:30:16,051 --> 00:30:17,380 or villains virtually 759 759 00:30:17,380 --> 00:30:18,213 instead of requiring us 760 760 00:30:18,213 --> 00:30:20,390 to dedicate two physical network interfaces 761 761 00:30:20,390 --> 00:30:22,960 and attaching a real patch cable between them. 762 762 00:30:22,960 --> 00:30:23,793 All right. 763 763 00:30:23,793 --> 00:30:26,820 I know that was a ton of information in this long video. 764 764 00:30:26,820 --> 00:30:28,810 So if I went too fast for you, 765 765 00:30:28,810 --> 00:30:31,380 please watch this lesson a second time. 766 766 00:30:31,380 --> 00:30:33,050 There is a lot of important information 767 767 00:30:33,050 --> 00:30:36,020 about IPv4 addressing that you just have to know. 768 768 00:30:36,020 --> 00:30:37,340 It is critical that you understand 769 769 00:30:37,340 --> 00:30:39,210 the different classes of IP addresses, 770 770 00:30:39,210 --> 00:30:40,760 the public and private IPs, 771 771 00:30:40,760 --> 00:30:42,350 and when each of these are used, 772 772 00:30:42,350 --> 00:30:44,690 as well as the different special IP addresses that we have 773 773 00:30:44,690 --> 00:30:47,233 such as the loopback, APIPA and others.