1 00:00:00,620 --> 00:00:08,120 So once again the format of an IP address in this case IP version 4 is a 32 bit binary number. 2 00:00:08,240 --> 00:00:15,290 It's divided into four parts or four octets which are 8 pets or one byte in size. 3 00:00:15,290 --> 00:00:22,280 So an IP address could be written as follows in binary in dotted decimal notation or it could be written 4 00:00:22,430 --> 00:00:23,780 as follows. 5 00:00:23,840 --> 00:00:26,510 Ducted decimal notation. 6 00:00:26,540 --> 00:00:35,900 So just to summarize it say for byte number or 32 bit number typically written in dotted decimal notation. 7 00:00:36,020 --> 00:00:40,230 But be aware that it's actually a binary address of 32 bits. 8 00:00:40,250 --> 00:00:42,010 Please refer to the binary videos. 9 00:00:42,020 --> 00:00:49,250 If you're not sure about the formatting or conversion of binary to decimal and back again and octet 10 00:00:49,400 --> 00:00:54,950 is 8 binary bets all one byte one byte equates to eight binary bits. 11 00:00:55,010 --> 00:01:01,970 So no provision for dress consists of four octets such as extra X to add extra X where X is an octet 12 00:01:02,110 --> 00:01:04,610 or 8 bits or one byte. 13 00:01:04,610 --> 00:01:10,610 Now using our street analogy again it's possible to have the same house number on different streets. 14 00:01:10,610 --> 00:01:15,290 So house one could be an Oxford Street as well as Cambridge Street. 15 00:01:15,290 --> 00:01:19,410 House Number One should just not appear twice on the same street. 16 00:01:19,460 --> 00:01:23,800 But number one is permitted on different streets in the same way here. 17 00:01:23,870 --> 00:01:31,730 It's possible to have number one on Network 10 but one dog 1.0 slash 24 as well as number one on network 18 00:01:31,950 --> 00:01:38,330 12:48 1.0 slushed 24 the same number can appear on different networks. 19 00:01:38,330 --> 00:01:40,240 I'll explain this next 24 in a moment. 20 00:01:40,280 --> 00:01:46,970 When we discuss network mosques but in this example we have network up one at 1.0 and told at one point 21 00:01:46,970 --> 00:01:54,980 1.0 and it's possible to have multiple devices with the host portion of the IP address set to one the 22 00:01:54,980 --> 00:02:02,500 same host portion can appear twice as I'm in this example or many times in a network or the internet. 23 00:02:02,600 --> 00:02:10,980 As long as the network portion is different now one thing you'll learn about networking is that things 24 00:02:10,980 --> 00:02:19,440 are constantly changing across classes or classful networks were used in the Internet from 1981 until 25 00:02:19,440 --> 00:02:27,730 the introduction of classless into domain routing in 1993 which is commonly known as cyder or C IDR. 26 00:02:27,780 --> 00:02:35,340 Now prior to 1993 address classes were used to divide the IP version 4 address space into five address 27 00:02:35,340 --> 00:02:36,380 classes. 28 00:02:36,690 --> 00:02:44,370 The three that we are going to concentrate on here are Class A B and C which are used for any cost traffic 29 00:02:44,860 --> 00:02:52,660 plus D is used for multicast and class-C is reserved for future or experimental purposes. 30 00:02:52,700 --> 00:03:00,450 Classes have been superseded in IP version 6 IP version 6 and does not use address classes and in IP 31 00:03:00,450 --> 00:03:04,430 version 4 address classes have been replaced with cyder. 32 00:03:04,650 --> 00:03:10,800 So the different classes of addresses a B and C were used to accomodate different sizes of networks 33 00:03:11,190 --> 00:03:14,170 which aided in the classification of those networks. 34 00:03:14,190 --> 00:03:20,910 So as an example a classful address supports about 16 million IP addresses. 35 00:03:20,910 --> 00:03:24,000 So once again we had plus a b and c.. 36 00:03:24,180 --> 00:03:27,620 These have been replaced with superseded by cyder. 37 00:03:27,780 --> 00:03:35,360 We'll see IDR and address classes such as A B and C were determined and then allocated by the owner 38 00:03:35,730 --> 00:03:38,440 or internet assigned numbers or 30. 39 00:03:38,520 --> 00:03:42,050 This format is not used entirely in its original format. 40 00:03:42,080 --> 00:03:47,250 Today he has an entry on Wikipedia showing the list of class addresses. 41 00:03:47,460 --> 00:03:52,200 So each class a address has approximately 16 million IP addresses. 42 00:03:52,200 --> 00:03:55,990 And if we scroll down the list we can see various examples. 43 00:03:56,040 --> 00:04:07,050 AT&T have 12 Xerox 13 HP 15 Dec. 16 so 15 and 16 are now owned by HP. 44 00:04:07,050 --> 00:04:12,740 Apple has 17 MIT 18 Ford 19 and so forth and so on. 45 00:04:13,050 --> 00:04:24,450 So notice as an example Apple own 17.00 doats arrow slash 8 Apple have 16 odd million public IP addresses 46 00:04:24,660 --> 00:04:26,920 that are part of the Class A address. 47 00:04:27,000 --> 00:04:35,740 So in the original IP address format across a address consists of eight network bits and 24 host bits. 48 00:04:35,880 --> 00:04:40,770 Hence it's written as shaped denoting eight network bets. 49 00:04:40,770 --> 00:04:46,770 Now this was fine when the Internet was small but it quickly became a limiting factor and thus multiple 50 00:04:46,770 --> 00:04:51,300 addresses were introduced with a different size and network portions. 51 00:04:51,300 --> 00:04:56,520 Hence we have class a class B and class C addresses. 52 00:04:56,610 --> 00:05:04,280 Please note once again that class full addresses were replaced in 1993 with plotless into domain routing 53 00:05:04,500 --> 00:05:07,320 or C ID are also called cyder. 54 00:05:07,650 --> 00:05:13,340 However you may still come across commands that use the classful address format. 55 00:05:13,380 --> 00:05:18,330 An example of that is the net work command within writing protocols. 56 00:05:18,560 --> 00:05:26,040 So as an example if you use the network command on a rope routing process the command is written in 57 00:05:26,040 --> 00:05:28,680 a class full format. 58 00:05:28,710 --> 00:05:33,660 It's also worth knowing a bit of the history and understanding why we have problems with a lack of IP 59 00:05:33,660 --> 00:05:35,030 addressing today. 60 00:05:35,190 --> 00:05:39,270 Hence it's worth your learning about potful addresses for completeness. 61 00:05:39,270 --> 00:05:44,880 The breaking up of addresses was originally used to try and save or conserv IP addresses but did not 62 00:05:44,880 --> 00:05:52,680 work in its original format and thus was expanded and changed by cyder well-explained side in a moment. 63 00:05:52,680 --> 00:05:56,540 Let's first look at the various address classes in more detail.