1 00:00:00,480 --> 00:00:01,470 In this lesson, 2 00:00:01,470 --> 00:00:04,530 we're going to talk about TCP/IP fundamentals, 3 00:00:04,530 --> 00:00:07,230 which are the very foundations of networking. 4 00:00:07,230 --> 00:00:09,750 Now, one of the major components of the operating system 5 00:00:09,750 --> 00:00:12,480 is networking because we have to be able to have networking, 6 00:00:12,480 --> 00:00:14,610 to communicate with the outside world. 7 00:00:14,610 --> 00:00:17,700 Networking is crucial for almost all modern systems, 8 00:00:17,700 --> 00:00:19,860 including those that run Linux. 9 00:00:19,860 --> 00:00:21,060 So in this lesson, 10 00:00:21,060 --> 00:00:23,430 we're going to review some of the fundamental concepts 11 00:00:23,430 --> 00:00:24,900 that are involved in networking, 12 00:00:24,900 --> 00:00:27,180 and then you're going to configure networking 13 00:00:27,180 --> 00:00:28,950 in your Linux systems. 14 00:00:28,950 --> 00:00:31,740 This will ensure your systems, especially your servers 15 00:00:31,740 --> 00:00:33,750 will be able to communicate with other computers, 16 00:00:33,750 --> 00:00:36,000 both locally and around the world. 17 00:00:36,000 --> 00:00:37,860 Before you start developing Linux specific 18 00:00:37,860 --> 00:00:39,210 networking skills, though, 19 00:00:39,210 --> 00:00:41,400 you need to review some fundamental concepts 20 00:00:41,400 --> 00:00:44,490 that comprise modern TCP/IP networks. 21 00:00:44,490 --> 00:00:46,830 Then you'll be better equipped to manage networking 22 00:00:46,830 --> 00:00:48,660 in your Linux systems. 23 00:00:48,660 --> 00:00:51,540 Now Linux offers all the necessary networking tools 24 00:00:51,540 --> 00:00:53,130 and features for integration 25 00:00:53,130 --> 00:00:55,410 into all types of network structures. 26 00:00:55,410 --> 00:00:57,540 Linux and other Unix operating systems 27 00:00:57,540 --> 00:00:59,910 use the TCP/IP protocol. 28 00:00:59,910 --> 00:01:02,250 It is not a single network protocol though, 29 00:01:02,250 --> 00:01:04,890 but instead it's a family of network protocols 30 00:01:04,890 --> 00:01:07,050 that offer various different services. 31 00:01:07,050 --> 00:01:08,790 Many families or suites of protocols 32 00:01:08,790 --> 00:01:10,320 have existed over the years. 33 00:01:10,320 --> 00:01:12,900 But these days, the only protocol suite 34 00:01:12,900 --> 00:01:16,050 that most people use is TCP/IP. 35 00:01:16,050 --> 00:01:19,200 Now another thing we need to talk about is the OSI model. 36 00:01:19,200 --> 00:01:22,530 The OSI model, or the Open Systems Interconnection model 37 00:01:22,530 --> 00:01:25,170 is used to standardize how networking is functioning 38 00:01:25,170 --> 00:01:28,020 inside of all of the different computer networking models 39 00:01:28,020 --> 00:01:29,850 and all the different protocols. 40 00:01:29,850 --> 00:01:32,760 Now, the OSI model is an abstraction that shows us 41 00:01:32,760 --> 00:01:34,500 how these things would work in an ideal 42 00:01:34,500 --> 00:01:36,270 or theoretical world. 43 00:01:36,270 --> 00:01:39,000 The OSI model has seven layers to it. 44 00:01:39,000 --> 00:01:40,830 And each of those layers represents 45 00:01:40,830 --> 00:01:43,680 an area of responsibility that has to be satisfied 46 00:01:43,680 --> 00:01:47,280 for the networking to be able to process and do its job. 47 00:01:47,280 --> 00:01:48,600 As an IT professional, 48 00:01:48,600 --> 00:01:51,180 you need to understand how these layers work. 49 00:01:51,180 --> 00:01:53,220 If we start at the top or layer seven, 50 00:01:53,220 --> 00:01:56,100 we have the application layer and the application layer 51 00:01:56,100 --> 00:01:58,500 supports applications and end-users. 52 00:01:58,500 --> 00:02:01,560 When you go to layer six, this is the presentation layer. 53 00:02:01,560 --> 00:02:04,049 This is where the formatting of data is going to occur, 54 00:02:04,049 --> 00:02:06,390 and cryptography is going to be handled. 55 00:02:06,390 --> 00:02:09,240 At layer five, we're going to have the session layer. 56 00:02:09,240 --> 00:02:11,280 This is used to establish, maintain, 57 00:02:11,280 --> 00:02:14,670 and tear down a connection between two different devices. 58 00:02:14,670 --> 00:02:17,010 Layer four is our transport layer. 59 00:02:17,010 --> 00:02:19,740 And this enables the reliable transmission of information 60 00:02:19,740 --> 00:02:22,470 using TCP or UDP. 61 00:02:22,470 --> 00:02:25,320 When we get down to layer three, we're at the network layer. 62 00:02:25,320 --> 00:02:27,750 Network layers are going to use logical addressing 63 00:02:27,750 --> 00:02:30,360 like IP addresses to tell data where to go 64 00:02:30,360 --> 00:02:31,800 on a given network. 65 00:02:31,800 --> 00:02:34,800 When we get down to layer two, we're at the data link layer. 66 00:02:34,800 --> 00:02:36,990 The data link layer is where we're going to be using 67 00:02:36,990 --> 00:02:39,540 physical addressing things like MAC addresses, 68 00:02:39,540 --> 00:02:42,150 to be able to send data around our local area network 69 00:02:42,150 --> 00:02:43,860 instead of across the internet. 70 00:02:43,860 --> 00:02:46,740 And finally layer one is our physical layer. 71 00:02:46,740 --> 00:02:49,230 This is actually the cables, the radio frequencies, 72 00:02:49,230 --> 00:02:51,930 and other things that enable physical network connectivity 73 00:02:51,930 --> 00:02:54,420 to occur between two different systems. 74 00:02:54,420 --> 00:02:57,390 Now, when you look at the TCP/IP protocol suite, 75 00:02:57,390 --> 00:03:00,240 it satisfies the requirements of the OSI model, 76 00:03:00,240 --> 00:03:02,580 but it does it in only four layers. 77 00:03:02,580 --> 00:03:07,050 This is also known as the TCP/IP model, or the DOD model. 78 00:03:07,050 --> 00:03:09,420 This suite is used to govern the network communications 79 00:03:09,420 --> 00:03:11,850 on most internal network and protocol suites 80 00:03:11,850 --> 00:03:13,320 on the internet too. 81 00:03:13,320 --> 00:03:16,350 Now, having an understanding of the TCP/IP suite can really 82 00:03:16,350 --> 00:03:18,810 aid in troubleshooting and network configuration, 83 00:03:18,810 --> 00:03:21,210 just like knowing the OSI model can. 84 00:03:21,210 --> 00:03:22,950 If you want to learn more about both of these, 85 00:03:22,950 --> 00:03:25,953 I do recommend you take a good course in Network Plus. 86 00:03:26,970 --> 00:03:28,710 Now, when we talk about networking, 87 00:03:28,710 --> 00:03:30,900 you'll often hear the term node. 88 00:03:30,900 --> 00:03:33,030 Now, a node is a term that refers to devices 89 00:03:33,030 --> 00:03:34,950 with an identity on the network. 90 00:03:34,950 --> 00:03:37,110 This can be a computer, it can be a server, 91 00:03:37,110 --> 00:03:38,850 it can be a tablet or a smartphone, 92 00:03:38,850 --> 00:03:40,710 really anything that's connected to the network 93 00:03:40,710 --> 00:03:41,940 can be a node. 94 00:03:41,940 --> 00:03:44,130 The identity of that node will be represented 95 00:03:44,130 --> 00:03:46,470 by a physical address, or a MAC address, 96 00:03:46,470 --> 00:03:49,200 or a logical address, like an IP address 97 00:03:49,200 --> 00:03:51,240 or an IP Version 6 address, 98 00:03:51,240 --> 00:03:54,450 or you can use any combination of those three. 99 00:03:54,450 --> 00:03:56,280 Now, when you're using a MAC address, 100 00:03:56,280 --> 00:03:58,260 this is the most fundamental network identity 101 00:03:58,260 --> 00:04:00,900 that's out there and it's considered a physical address 102 00:04:00,900 --> 00:04:02,910 and it operates at the data link layer 103 00:04:02,910 --> 00:04:05,310 or layer two of the OSI model. 104 00:04:05,310 --> 00:04:06,960 If you're using an IP address, 105 00:04:06,960 --> 00:04:09,060 this is considered a logical address. 106 00:04:09,060 --> 00:04:11,940 And an IP address is going to be used at layer three 107 00:04:11,940 --> 00:04:14,670 or the network layer of the OSI model. 108 00:04:14,670 --> 00:04:17,190 When you're using an IP address, most commonly, 109 00:04:17,190 --> 00:04:21,180 you're going to see an IPv4 address or Version 4 address. 110 00:04:21,180 --> 00:04:23,130 Now these Version 4 address are written 111 00:04:23,130 --> 00:04:24,930 in dotted decimal notation, 112 00:04:24,930 --> 00:04:26,970 which is written in base 10 numbers. 113 00:04:26,970 --> 00:04:30,270 These are going to have a range from zero to 255 114 00:04:30,270 --> 00:04:31,890 in each of four positions. 115 00:04:31,890 --> 00:04:34,173 And each one is going to be separated by a dot. 116 00:04:36,218 --> 00:04:39,570 So something like one 192.168.2.1 117 00:04:39,570 --> 00:04:42,300 would be an IP Version 4 address. 118 00:04:42,300 --> 00:04:45,510 Now, a computer though, doesn't use addresses in decimal. 119 00:04:45,510 --> 00:04:48,240 Instead, they like to look at things in binary, 120 00:04:48,240 --> 00:04:51,210 which means everything has to be written as a zero or a one. 121 00:04:51,210 --> 00:04:54,630 So it would take that address and convert it into binary 122 00:04:54,630 --> 00:04:56,340 for use on the network. 123 00:04:56,340 --> 00:04:58,110 Now, on the other hand, we, as humans, 124 00:04:58,110 --> 00:05:00,270 don't really like to have to memorize numbers. 125 00:05:00,270 --> 00:05:01,950 So instead we like to look at things 126 00:05:01,950 --> 00:05:05,070 in human-readable format, something like a host name. 127 00:05:05,070 --> 00:05:07,770 So that IP address can also be represented 128 00:05:07,770 --> 00:05:09,450 by the host name of the node. 129 00:05:09,450 --> 00:05:11,580 For example, if you go to my web server, 130 00:05:11,580 --> 00:05:13,380 it's diontraining.com, 131 00:05:13,380 --> 00:05:16,350 instead of you having to type in the exact IP address. 132 00:05:16,350 --> 00:05:19,020 Now the host name is this human-readable name 133 00:05:19,020 --> 00:05:21,180 that helps people better understand what device 134 00:05:21,180 --> 00:05:22,740 they're actually working with. 135 00:05:22,740 --> 00:05:25,680 On the internet we use domain names for this purpose, 136 00:05:25,680 --> 00:05:27,240 but on your local intranet, 137 00:05:27,240 --> 00:05:29,970 you can use a host name instead like server, 138 00:05:29,970 --> 00:05:34,590 or database server or payroll server or something like that. 139 00:05:34,590 --> 00:05:36,570 This identity will often be configured 140 00:05:36,570 --> 00:05:38,820 during the installation of the operating system. 141 00:05:38,820 --> 00:05:42,780 And often we call this the computer name or the host name. 142 00:05:42,780 --> 00:05:45,570 Now there's also several essential network devices out there 143 00:05:45,570 --> 00:05:47,640 and different components that you need to understand 144 00:05:47,640 --> 00:05:49,890 so you can figure out how all these things work. 145 00:05:49,890 --> 00:05:51,390 These can be part of your troubleshooting, 146 00:05:51,390 --> 00:05:54,420 or it can also be used during network installation. 147 00:05:54,420 --> 00:05:56,820 Now Linux systems need to be configured properly 148 00:05:56,820 --> 00:05:59,610 to interact with different network devices and components 149 00:05:59,610 --> 00:06:02,130 to able to perform their functions on the network. 150 00:06:02,130 --> 00:06:04,500 The first one we're going to talk about is a switch. 151 00:06:04,500 --> 00:06:06,900 Now, a switch is a device that acts as a concentrator 152 00:06:06,900 --> 00:06:09,120 and it centralizes all network connections 153 00:06:09,120 --> 00:06:12,990 for a given segment to a single device, known as a switch. 154 00:06:12,990 --> 00:06:14,850 This switch can be used to manage traffic 155 00:06:14,850 --> 00:06:17,550 for performance and security concerns as well. 156 00:06:17,550 --> 00:06:20,130 As a general rule switches work at layer two 157 00:06:20,130 --> 00:06:21,300 of the OSI model, 158 00:06:21,300 --> 00:06:23,910 and they do their switching using MAC addresses. 159 00:06:23,910 --> 00:06:25,710 If we want to operate at layer three, 160 00:06:25,710 --> 00:06:27,360 we're going to use a router. 161 00:06:27,360 --> 00:06:29,790 Now, a router is a device that acts as a central point 162 00:06:29,790 --> 00:06:32,640 for communications between different network segments 163 00:06:32,640 --> 00:06:35,670 and they connect two different networks together. 164 00:06:35,670 --> 00:06:37,680 Now, administrators can configure the router 165 00:06:37,680 --> 00:06:40,020 to permit or deny certain kinds of traffic 166 00:06:40,020 --> 00:06:41,730 using access control lists, 167 00:06:41,730 --> 00:06:43,560 as well as the ability to pass traffic 168 00:06:43,560 --> 00:06:45,570 from one network segment to another, 169 00:06:45,570 --> 00:06:48,210 such as going from your internal network to the internet, 170 00:06:48,210 --> 00:06:50,040 which is an external network. 171 00:06:50,040 --> 00:06:51,990 These routers are going to operate at layer three 172 00:06:51,990 --> 00:06:53,610 of the OSI model, like I said, 173 00:06:53,610 --> 00:06:56,220 and they use IP addresses either Version 4 174 00:06:56,220 --> 00:06:58,380 or Version 6 by default. 175 00:06:58,380 --> 00:07:01,020 Now media is another term you have to be aware of. 176 00:07:01,020 --> 00:07:03,180 Media just refers to the actual path 177 00:07:03,180 --> 00:07:05,130 that we're going to send the electrical signals over 178 00:07:05,130 --> 00:07:07,590 to go from one device or component to another. 179 00:07:07,590 --> 00:07:09,600 Now, most typically we're going to be using 180 00:07:09,600 --> 00:07:11,190 network cables for this purpose. 181 00:07:11,190 --> 00:07:14,040 Specifically, twisted pair ethernet cables. 182 00:07:14,040 --> 00:07:15,750 Now these twisted pair cables can come in, 183 00:07:15,750 --> 00:07:19,530 either shielded or STP or unshielded UTP Versions. 184 00:07:19,530 --> 00:07:22,860 Just like you learned about back in A Plus and Network Plus. 185 00:07:22,860 --> 00:07:24,480 When dealing with these type of cables, 186 00:07:24,480 --> 00:07:27,330 it is relatively inexpensive and easy to work with. 187 00:07:27,330 --> 00:07:30,240 Now, another type of cable you might use is fiber cables. 188 00:07:30,240 --> 00:07:31,590 They're harder to work with. 189 00:07:31,590 --> 00:07:32,970 They're a little bit more expensive, 190 00:07:32,970 --> 00:07:35,610 but they do give you a lot better performance. 191 00:07:35,610 --> 00:07:38,250 Additionally, when we're talking about layer one devices 192 00:07:38,250 --> 00:07:39,810 like these two types of cables, 193 00:07:39,810 --> 00:07:42,270 we also need to consider radiofrequency. 194 00:07:42,270 --> 00:07:44,520 If you're using wireless networks, you're going to be using 195 00:07:44,520 --> 00:07:47,790 radiofrequency waves that are basically invisible cables 196 00:07:47,790 --> 00:07:49,263 to connect your two devices. 197 00:07:50,190 --> 00:07:51,734 All right, now that we've covered some of the main devices 198 00:07:51,734 --> 00:07:54,060 and components inside of our networks, 199 00:07:54,060 --> 00:07:56,550 let's talk about the data as it moves through the network 200 00:07:56,550 --> 00:07:58,020 at different layers. 201 00:07:58,020 --> 00:08:00,330 When we talk about data, it's called different things, 202 00:08:00,330 --> 00:08:02,310 depending on what layer we're operating at 203 00:08:02,310 --> 00:08:06,090 inside the TCP/IP network, or the OSI model. 204 00:08:06,090 --> 00:08:08,070 If we're going to be operating at the network layer 205 00:08:08,070 --> 00:08:10,170 of the OSI model or layer three, 206 00:08:10,170 --> 00:08:12,690 we're going to refer to this data as a packet. 207 00:08:12,690 --> 00:08:15,540 Now, when we get down to layer two or the data link layer, 208 00:08:15,540 --> 00:08:17,730 we're going to refer to it as a frame. 209 00:08:17,730 --> 00:08:20,520 When we get down to layer one or the physical layer, 210 00:08:20,520 --> 00:08:23,790 we're going to call it a bit, which is a one or zero. 211 00:08:23,790 --> 00:08:25,890 It's just the amount of data that we're grouping together 212 00:08:25,890 --> 00:08:27,180 at these different layers. 213 00:08:27,180 --> 00:08:28,560 That's going to give it a different name, 214 00:08:28,560 --> 00:08:32,280 whether it's a bit, a frame, or a packet. 215 00:08:32,280 --> 00:08:34,289 Now, when we're dealing with network services, 216 00:08:34,289 --> 00:08:36,570 we have a lot of different network services on the network, 217 00:08:36,570 --> 00:08:38,940 but two are very, very important to us. 218 00:08:38,940 --> 00:08:41,760 And these are DNS and DHCP. 219 00:08:41,760 --> 00:08:43,320 Now you're going to have to understand the role 220 00:08:43,320 --> 00:08:44,820 of these two different services 221 00:08:44,820 --> 00:08:47,160 if you want to properly configure your Linux systems 222 00:08:47,160 --> 00:08:48,570 to use the network. 223 00:08:48,570 --> 00:08:51,360 First, we have DNS, and DNS stands for 224 00:08:51,360 --> 00:08:53,220 the Domain Name System. 225 00:08:53,220 --> 00:08:55,800 This is a service that provides name resolution. 226 00:08:55,800 --> 00:08:58,440 It's a way of creating easy to remember host names 227 00:08:58,440 --> 00:09:00,780 with a difficult to remember IP address. 228 00:09:00,780 --> 00:09:02,910 Again, remember I said, if you go to my website, 229 00:09:02,910 --> 00:09:04,384 it's diontraining.com. 230 00:09:04,384 --> 00:09:06,330 That is the domain name. 231 00:09:06,330 --> 00:09:09,570 And DNS allows you to type in diontraining.com 232 00:09:09,570 --> 00:09:11,970 and will automatically convert it to the IP address 233 00:09:11,970 --> 00:09:14,430 that's really associated with that server. 234 00:09:14,430 --> 00:09:17,100 DNS is going to be implemented as a database that's hosted 235 00:09:17,100 --> 00:09:20,580 on one or more servers as part of this DNS system. 236 00:09:20,580 --> 00:09:23,850 This database can contain the names and the IP addresses 237 00:09:23,850 --> 00:09:25,800 for all the nodes in your own network, 238 00:09:25,800 --> 00:09:29,760 or it can be part of the larger internet DNS infrastructure. 239 00:09:29,760 --> 00:09:31,260 So when I'm talking about my website, 240 00:09:31,260 --> 00:09:33,900 that's part of the larger internet DNS structure, 241 00:09:33,900 --> 00:09:36,150 but I also have a local DNS server 242 00:09:36,150 --> 00:09:38,193 for the servers internal to my network. 243 00:09:39,030 --> 00:09:41,850 Next, we need to talk about DHCP. 244 00:09:41,850 --> 00:09:44,280 You see, all of the different computers and tablets, 245 00:09:44,280 --> 00:09:47,070 and mobile devices, and servers, need to be configured 246 00:09:47,070 --> 00:09:49,080 with some basic information in order for them 247 00:09:49,080 --> 00:09:51,030 to make a connection on the network. 248 00:09:51,030 --> 00:09:53,010 We can do this in one of two ways. 249 00:09:53,010 --> 00:09:55,560 We can do it statically or dynamically. 250 00:09:55,560 --> 00:09:57,870 A static configuration is when somebody goes 251 00:09:57,870 --> 00:10:00,360 and manually configures this information on the servers 252 00:10:00,360 --> 00:10:01,590 or network devices. 253 00:10:01,590 --> 00:10:05,040 But dynamic configuration is a lot easier to use, 254 00:10:05,040 --> 00:10:06,090 especially when we're dealing 255 00:10:06,090 --> 00:10:08,370 with a lot of end-user workstations. 256 00:10:08,370 --> 00:10:12,150 With a dynamic configuration we're going to use DHCP 257 00:10:12,150 --> 00:10:15,150 or a Dynamic Host Configuration Protocol. 258 00:10:15,150 --> 00:10:18,120 DHCP is a service that provides dynamic configuration 259 00:10:18,120 --> 00:10:20,340 of your endpoint devices by providing them 260 00:10:20,340 --> 00:10:23,760 with their IP address, their subnet mask, their gateway, 261 00:10:23,760 --> 00:10:26,100 and their DNS server to use. 262 00:10:26,100 --> 00:10:29,040 Now, IP addresses are going to use an addressing system 263 00:10:29,040 --> 00:10:31,380 for managing your different network identities. 264 00:10:31,380 --> 00:10:33,090 When we deal with IPv4, 265 00:10:33,090 --> 00:10:35,130 we're dealing with a very old protocol. 266 00:10:35,130 --> 00:10:38,040 It was actually defined all the way back in 1981, 267 00:10:38,040 --> 00:10:40,710 and the addresses were 32-bits in length. 268 00:10:40,710 --> 00:10:44,610 And this gives us about 4.2 billion addresses out there. 269 00:10:44,610 --> 00:10:48,510 Now IPv4 are going to be divided into at least two portions. 270 00:10:48,510 --> 00:10:50,430 We have a network identifier portion 271 00:10:50,430 --> 00:10:52,500 and a host identifier portion. 272 00:10:52,500 --> 00:10:54,965 The network identifier is going to define the network segment 273 00:10:54,965 --> 00:10:56,880 that that host belongs to. 274 00:10:56,880 --> 00:10:59,850 And the host identifier uniquely identifies the host 275 00:10:59,850 --> 00:11:01,530 within that segment. 276 00:11:01,530 --> 00:11:05,490 Now these approximately 4.2 billion IPv4 addresses 277 00:11:05,490 --> 00:11:08,010 are going to be divided into five different classes 278 00:11:08,010 --> 00:11:11,850 and they're labeled A, B, C, D, and E. 279 00:11:11,850 --> 00:11:15,060 These classes provide a framework for possible segmentation 280 00:11:15,060 --> 00:11:16,440 of our different networks. 281 00:11:16,440 --> 00:11:19,380 And each class provides a specified number of networks, 282 00:11:19,380 --> 00:11:22,470 as well as the number of hosts available on each network. 283 00:11:22,470 --> 00:11:25,170 For the first three classes, A, B, and C, 284 00:11:25,170 --> 00:11:27,960 the division is going to occur based on the network ID 285 00:11:27,960 --> 00:11:30,570 and the host ID based on one of the dots 286 00:11:30,570 --> 00:11:32,790 in this decimal dotted notation. 287 00:11:32,790 --> 00:11:36,030 Network professionals can easily recognize which class it is 288 00:11:36,030 --> 00:11:37,890 by the value of the first octet. 289 00:11:37,890 --> 00:11:40,320 And then they'll know the default subnet mask 290 00:11:40,320 --> 00:11:42,060 for each of those classes. 291 00:11:42,060 --> 00:11:44,820 For example, a class A address is going to start out 292 00:11:44,820 --> 00:11:47,640 with a zero, dot something, dot something, dot something, 293 00:11:47,640 --> 00:11:49,620 all the way up to 127, 294 00:11:49,620 --> 00:11:51,600 dot something, dot something, dot something. 295 00:11:51,600 --> 00:11:54,300 So as long as you have something between zero and 127 296 00:11:54,300 --> 00:11:57,810 as your first octet, you know, it's a class A address. 297 00:11:57,810 --> 00:11:59,340 If you're dealing with class B, 298 00:11:59,340 --> 00:12:01,800 it's first octet is going to start with a 128. 299 00:12:01,800 --> 00:12:04,110 So all of its addresses are going to be 128, 300 00:12:04,110 --> 00:12:05,910 dot something, dot something, dot something, 301 00:12:05,910 --> 00:12:07,890 all the way up to 191, 302 00:12:07,890 --> 00:12:09,900 dot something, dot something, dot something. 303 00:12:09,900 --> 00:12:12,000 And so if you have something with the first octet 304 00:12:12,000 --> 00:12:16,740 of 128 to 191, you know, this is a class B address. 305 00:12:16,740 --> 00:12:21,360 With class C, we're going to start out with 192.0.0.0, 306 00:12:21,360 --> 00:12:22,410 and go all the way up 307 00:12:23,620 --> 00:12:26,577 to 223.255.255.255. 308 00:12:26,577 --> 00:12:30,210 And this tells us that anything that starts out with a 192, 309 00:12:30,210 --> 00:12:34,080 going up to a 223 is going to be a class C address. 310 00:12:34,080 --> 00:12:35,940 When we get to a class D address, 311 00:12:35,940 --> 00:12:40,050 we're going to have a starting address of 224.0.0.0, 312 00:12:40,050 --> 00:12:41,100 and an ending address 313 00:12:43,010 --> 00:12:45,240 of 239.255.255.255. 314 00:12:45,240 --> 00:12:47,550 So again, if we start out with 224 315 00:12:47,550 --> 00:12:49,680 and we go all the way up to 239, 316 00:12:49,680 --> 00:12:51,810 that is going to be in our first octet and telling us 317 00:12:51,810 --> 00:12:53,880 that it is a class D address. 318 00:12:53,880 --> 00:12:56,040 Finally, we have a class E address, 319 00:12:56,040 --> 00:13:00,210 and this is going to have a starting address of 240.0.0.0, 320 00:13:00,210 --> 00:13:01,260 and an ending address 321 00:13:03,104 --> 00:13:04,980 of 255.255.255.255. 322 00:13:04,980 --> 00:13:08,580 So if you have anything between 240 and 255 323 00:13:08,580 --> 00:13:09,840 in that first octet, 324 00:13:09,840 --> 00:13:12,600 you know, you're dealing with a class E address. 325 00:13:12,600 --> 00:13:15,480 Now, in addition to knowing these five IP address classes, 326 00:13:15,480 --> 00:13:18,210 there's several other IP addresses or address ranges 327 00:13:18,210 --> 00:13:20,610 that are pretty important to us in networking. 328 00:13:20,610 --> 00:13:24,090 Now because of the depletion of IPv4 addresses over time, 329 00:13:24,090 --> 00:13:26,730 and there's only 4.2 billion or so of these, 330 00:13:26,730 --> 00:13:29,550 there are three IP address ranges that we reserve 331 00:13:29,550 --> 00:13:31,950 for internal use inside your network. 332 00:13:31,950 --> 00:13:34,200 These are known as private IPs. 333 00:13:34,200 --> 00:13:37,380 Now this class A reserved range for a private IP address 334 00:13:37,380 --> 00:13:39,210 is anything that starts with a 10. 335 00:13:39,210 --> 00:13:41,580 So if you have 10.0.0.0, 336 00:13:41,580 --> 00:13:45,480 all the way up through 10.255.255.255, 337 00:13:45,480 --> 00:13:48,150 that is considered the private class A range. 338 00:13:48,150 --> 00:13:51,300 And that gives us 16.7 million addresses 339 00:13:51,300 --> 00:13:53,790 that we can choose from as private addresses. 340 00:13:53,790 --> 00:13:55,440 If we're going to do this in class B, 341 00:13:55,440 --> 00:13:56,590 the class B reserved 342 00:13:58,041 --> 00:14:00,897 or private range is 172.16.0.0 343 00:14:02,043 --> 00:14:05,460 all the way up to 172.31.255.255 344 00:14:05,460 --> 00:14:09,300 So if the first two octets start with 172.16, 345 00:14:09,300 --> 00:14:14,300 up through 172.31, that is a private class B address. 346 00:14:14,310 --> 00:14:16,350 And finally we have the class C range. 347 00:14:16,350 --> 00:14:18,670 The class C reserved or private address range 348 00:14:20,460 --> 00:14:21,897 is 192.168.0.0 349 00:14:23,181 --> 00:14:26,820 all the way up to 192.168.255.255. 350 00:14:26,820 --> 00:14:30,420 So if you have an address that starts with 192.168, 351 00:14:30,420 --> 00:14:32,070 dot something, dot something, 352 00:14:32,070 --> 00:14:35,220 that is going to be a class C private address. 353 00:14:35,220 --> 00:14:36,720 Now there's a couple of other addresses 354 00:14:36,720 --> 00:14:39,000 that we need to talk about as well, that are special. 355 00:14:39,000 --> 00:14:41,190 One of these is the loopback address. 356 00:14:41,190 --> 00:14:44,250 Now the loopback address is used for diagnostic purposes, 357 00:14:44,250 --> 00:14:47,670 and it gives the system the ability to network with itself. 358 00:14:47,670 --> 00:14:52,230 This is known as 127.0.0.1 by default. 359 00:14:52,230 --> 00:14:54,840 Another one we have is the link-local range, 360 00:14:54,840 --> 00:14:57,000 which is used for zero configuration LANs, 361 00:14:57,000 --> 00:14:59,850 or when the DHCP lease generation fails to work, 362 00:14:59,850 --> 00:15:01,860 and this is also known as APIPA 363 00:15:01,860 --> 00:15:04,230 or the Automatic Private IP Addressing. 364 00:15:04,230 --> 00:15:07,050 This link-local or APIPA range is any address 365 00:15:07,050 --> 00:15:11,823 that starts with 169.254, dot something dot something. 366 00:15:12,690 --> 00:15:15,720 Now IPv4 is pretty useful and it's still used 367 00:15:15,720 --> 00:15:16,980 pretty heavily these days, 368 00:15:16,980 --> 00:15:20,340 even though it was created all the way back in 1981. 369 00:15:20,340 --> 00:15:23,520 But over time, we started running into some limitations 370 00:15:23,520 --> 00:15:26,610 specifically the fact that we only have 4.2 billion 371 00:15:26,610 --> 00:15:28,110 or so IP addresses. 372 00:15:28,110 --> 00:15:32,310 So a newer standard was released known as IP Version 6. 373 00:15:32,310 --> 00:15:35,910 IP Version 6 fixed a lot of the weaknesses of IPv4, 374 00:15:35,910 --> 00:15:38,280 and it has a much larger address space 375 00:15:38,280 --> 00:15:39,780 as well as built-in encryption 376 00:15:39,780 --> 00:15:42,360 and a more efficient routing mechanism. 377 00:15:42,360 --> 00:15:45,480 We're not going to dive too deep into IPv6 right now, 378 00:15:45,480 --> 00:15:47,310 but again, this will going to be something that's a review 379 00:15:47,310 --> 00:15:49,740 from your A Plus or Network Plus studies. 380 00:15:49,740 --> 00:15:53,520 Remember that IPv6, instead of using a 32-bit number 381 00:15:53,520 --> 00:15:55,860 is going to use 128-bit number, 382 00:15:55,860 --> 00:15:58,440 giving us a lot more addresses out there. 383 00:15:58,440 --> 00:16:03,210 In fact, we have 340 undecillion IP addresses in IPv6 384 00:16:03,210 --> 00:16:07,980 versus the 4.2 or 4.3 billion that we have in IPv4. 385 00:16:07,980 --> 00:16:10,500 Another thing we need to discuss is port numbers. 386 00:16:10,500 --> 00:16:11,550 You're probably familiar with this, 387 00:16:11,550 --> 00:16:13,320 again from your A Plus, Network Plus, 388 00:16:13,320 --> 00:16:14,670 and Security Plus studies, 389 00:16:14,670 --> 00:16:17,070 but network port numbers are numerical values 390 00:16:17,070 --> 00:16:19,740 that are assigned to various application layer protocols 391 00:16:19,740 --> 00:16:22,350 like FTP is port 21. 392 00:16:22,350 --> 00:16:25,920 SSH is port 22 and things like that. 393 00:16:25,920 --> 00:16:28,500 Now your network devices are going to use these port numbers 394 00:16:28,500 --> 00:16:30,750 to understand what application is going to handle 395 00:16:30,750 --> 00:16:33,030 the communication for that particular device 396 00:16:33,030 --> 00:16:34,380 over the network. 397 00:16:34,380 --> 00:16:36,900 Humans work with application layer protocols by name 398 00:16:36,900 --> 00:16:37,830 all the time. 399 00:16:37,830 --> 00:16:40,980 Things like HTTP or the Hypertext Transfer Protocol, 400 00:16:40,980 --> 00:16:44,820 for example, but a computer needs to know the port number. 401 00:16:44,820 --> 00:16:47,400 So HTTP is port 80. 402 00:16:47,400 --> 00:16:48,750 If you're going to use something like 403 00:16:48,750 --> 00:16:50,730 Post Office Protocol version 3, 404 00:16:50,730 --> 00:16:53,670 which you use for email that's port 110. 405 00:16:53,670 --> 00:16:56,700 If you're going to use Hypertext Transfer Protocol Secure 406 00:16:56,700 --> 00:17:00,090 that's port 443 and things like that. 407 00:17:00,090 --> 00:17:02,610 Again, going back to your A Plus, Network Plus, 408 00:17:02,610 --> 00:17:04,020 and Security Plus studies, 409 00:17:04,020 --> 00:17:06,329 you should be familiar with what different ports are 410 00:17:06,329 --> 00:17:07,829 for particular applications 411 00:17:07,829 --> 00:17:09,540 that are very popular in the world. 412 00:17:09,540 --> 00:17:12,960 Things like POP3, IMAP, HTTP, 413 00:17:12,960 --> 00:17:15,631 HTTPS, SSH, FTP, 414 00:17:15,631 --> 00:17:17,819 Telnet and more. 415 00:17:17,819 --> 00:17:19,859 Network administrators are also going to divide up 416 00:17:19,859 --> 00:17:21,510 your network into segments. 417 00:17:21,510 --> 00:17:24,060 And this allows us to better manage our network traffic 418 00:17:24,060 --> 00:17:25,980 and reduce some of the congestion. 419 00:17:25,980 --> 00:17:28,890 Our goal here is to manage traffic more efficiently 420 00:17:28,890 --> 00:17:30,180 and more effectively, 421 00:17:30,180 --> 00:17:32,550 and this results in better network performance, 422 00:17:32,550 --> 00:17:34,350 and allows us to isolate traffic 423 00:17:34,350 --> 00:17:35,850 that we want out of our networks 424 00:17:35,850 --> 00:17:37,890 based on the purposes of security. 425 00:17:37,890 --> 00:17:39,660 The logical divisions of our network 426 00:17:39,660 --> 00:17:41,730 are going to be referred to as subnets 427 00:17:41,730 --> 00:17:44,010 and they're referred to by a network ID. 428 00:17:44,010 --> 00:17:46,680 This network ID is going to be part of the IP address 429 00:17:46,680 --> 00:17:48,660 for each node that we're going to be using 430 00:17:48,660 --> 00:17:50,490 and all those nodes in that subnet 431 00:17:50,490 --> 00:17:53,520 will have the same network ID in their IP address. 432 00:17:53,520 --> 00:17:55,830 This means the same beginning part is going to be used 433 00:17:55,830 --> 00:17:58,620 by all the devices on that particular network. 434 00:17:58,620 --> 00:18:00,990 Now, each node is going to have its own unique host ID 435 00:18:00,990 --> 00:18:03,573 within that subnet too, to identify itself. 436 00:18:04,470 --> 00:18:07,110 So, for example, let's say I have a computer network 437 00:18:07,110 --> 00:18:08,550 with 10 machines on it, 438 00:18:08,550 --> 00:18:11,280 and I want to have them using a private IP address range 439 00:18:11,280 --> 00:18:12,663 in the class C network. 440 00:18:13,800 --> 00:18:17,850 I might assign the network as 192.168.1.0 441 00:18:17,850 --> 00:18:19,650 as my network ID. 442 00:18:19,650 --> 00:18:23,010 Then I'm going to have all of my IP addresses for my individual 443 00:18:23,010 --> 00:18:25,323 machines being part of that network. 444 00:18:26,511 --> 00:18:29,880 So the router might be 192.168.1.1. 445 00:18:29,880 --> 00:18:33,930 The first computer might be 192.168.1.2. 446 00:18:33,930 --> 00:18:38,820 The second computer would be 192.168.1.3 and so on. 447 00:18:38,820 --> 00:18:40,290 Now notice they're all going to start 448 00:18:40,290 --> 00:18:42,270 with the same first three octets, 449 00:18:42,270 --> 00:18:44,850 because I'm dealing with the standard class C network, 450 00:18:44,850 --> 00:18:48,870 and that's why I have 192.168.1 dot something. 451 00:18:48,870 --> 00:18:53,870 And all of those are part of that address of 192.168.1.0 452 00:18:54,390 --> 00:18:56,280 which is my network ID. 453 00:18:56,280 --> 00:18:58,620 Again, if you're not getting the concept of subnetting, 454 00:18:58,620 --> 00:19:00,122 I definitely recommend going back 455 00:19:00,122 --> 00:19:02,160 and looking at your Network Plus studies, 456 00:19:02,160 --> 00:19:04,140 because that is something that is covered in that course 457 00:19:04,140 --> 00:19:05,343 in a lot more depth.