1 00:00:00,624 --> 00:00:07,065 In the previous video, we already learn about Public IP Address and Private IP Address. 2 00:00:07,453 --> 00:00:12,169 Now in this video we are going to start learning about subnetting. 3 00:00:13,260 --> 00:00:17,101 Okay, do you remember why we need to learn subnetting? 4 00:00:17,570 --> 00:00:23,762 Yes! We need to learn subnetting to determine the best prefix we will use in the network. 5 00:00:24,400 --> 00:00:28,240 For example, here we have a computer network that consist 6 00:00:28,240 --> 00:00:35,333 of 12 computers. So in this case, we will need 12 IP for each computers. 7 00:00:35,760 --> 00:00:42,046 The question is, which prefix is the best for 12 IP or 12 computers? 8 00:00:43,018 --> 00:00:51,245 In the previous video, I say that if we use prefix /24, the total IP is 256. 9 00:00:52,792 --> 00:00:59,145 How we can get this 256? we are going to learn about this now. 10 00:00:59,760 --> 00:01:07,493 To get this 256 is 2 to the power of 32 minus prefix. 11 00:01:08,043 --> 00:01:19,621 In this case, the prefix is 24, so the total IP is 2 to the power of 8. Because 32 minus 24 12 00:01:19,621 --> 00:01:31,718 is 8. And 2 to the power of 8 is 256. This is how we get 256 for prefix /24. 13 00:01:32,800 --> 00:01:40,547 The question is, why 32? this is because IP Address is consist of 32 bit. 14 00:01:41,367 --> 00:01:47,607 Oh ya, this formula is the easyway to learn about subnetting. If you want to learn 15 00:01:47,607 --> 00:01:53,845 subnetting in the hardway, you will need to convert this IP Address to binary first, 16 00:01:53,977 --> 00:01:59,733 doing some calculation in the binary, and then convert it back to the decimal. 17 00:02:00,188 --> 00:02:04,242 I will not teach you the hardway in this course. 18 00:02:04,646 --> 00:02:11,239 Because if we learn in the hardway, everyone of you will think that computer network is difficult! 19 00:02:11,744 --> 00:02:16,621 In this course, I want to make the computer network as simple as possible. 20 00:02:16,820 --> 00:02:20,285 So you can happy to learn about computer network. 21 00:02:21,046 --> 00:02:32,102 Okay, back to this. Now let’s review this again, so here we have prefix /24, the total IP is 256, 22 00:02:32,278 --> 00:02:48,926 we can get this 256 from 2 to the power of 32 minus prefix, 32 minus 24 is 8. And 2 to the power of 8 is 256. 23 00:02:49,599 --> 00:02:58,793 May be some of you have a trouble to determine 2 to the power of 8. So I will give you another easier example. 24 00:02:58,983 --> 00:03:06,482 Let’s say we have prefix /30. How many IP Address that we can use in prefix /30? 25 00:03:08,420 --> 00:03:17,370 2 to the power of 32 minus 30, 32 minus 30 is 2, so 2 to the power of 2, 26 00:03:17,701 --> 00:03:24,869 I think all of you will know the answer right? Yes.. 2 to the power of 2 Is 4. 27 00:03:25,584 --> 00:03:35,199 Now let’s try another example. Let’s say we have prefix /29. How many IP Address that we can use 28 00:03:35,199 --> 00:03:45,874 in prefix /29? Let’s try to calculate. 2 to the power of 32 minus 29. 32 minus 29 29 00:03:45,874 --> 00:03:58,649 is 3, so 2 to the power of 3, the answer is 8. So the total IP that we can use in prefix /29 is 8, 30 00:03:59,547 --> 00:04:07,485 Well, if you see here, actually we have a patterns. 2 to the power of 2 is 4, 31 00:04:07,778 --> 00:04:18,373 2 to the power of 3 is 8. This is means that if the power increment by 1, the result is multiply by 2. 32 00:04:19,360 --> 00:04:31,981 Let’s write it out. 2 to the power of 1 is 2, 2 to the power of 2 is 4, 2 to the power of 3 is 8, 33 00:04:32,632 --> 00:04:41,840 2 to the power of 4 is 16, 2 to the power of 5 is 32, and others. 34 00:04:42,392 --> 00:04:49,565 If you see the patterns, here we just need to multiply the result by 2. 2 to the power of 2 35 00:04:49,565 --> 00:05:00,075 is 2 multiply by 2, which is 4. 2 to the power of 3 is 4 multiply by 2, which is 8. 36 00:05:00,755 --> 00:05:12,715 2 to the power of 4 is 8 multiply by 2, which is 16. 2 to the power of 5 is 16 multiply by 2, 37 00:05:12,791 --> 00:05:24,043 which is 32, 2 to the power of 6 is 32 multiply by 2, which is 64. 2 to the power of 7 38 00:05:24,043 --> 00:05:38,675 is 64 multiply by 2, which is 128, and 2 to the power of 8 is 128 multiply by 2, which is 256. 39 00:05:39,243 --> 00:05:44,261 So the pattern is that we just need to multiply the result by 2. 40 00:05:44,261 --> 00:05:48,625 We don’t need to have a trouble to calculating powers anymore. 41 00:05:49,645 --> 00:05:59,527 Okay, here we stop in 2 to the power of 8. Because this is for prefix /24, in this course we will only 42 00:05:59,527 --> 00:06:10,000 learn about subnetting prefix /24 until /30. So we just need to know until 2 to the power of 8. 43 00:06:10,704 --> 00:06:14,079 Okay, now I hope you understand how to determine 44 00:06:14,079 --> 00:06:18,082 how much IP Address that we can use in the specific prefix. 45 00:06:18,720 --> 00:06:25,661 Before I end this video, let’s try one more example to make sure that you really understand. 46 00:06:26,042 --> 00:06:40,534 Let’s say we have prefix /26, the total IP for this prefix is 2 to the power of 32 minus 26. 32 minus 26 is 6, 47 00:06:40,835 --> 00:06:53,835 so 2 to the power of 6, and the result is 64. So the total IP that we can use in prefix /26 is 64. 48 00:06:54,574 --> 00:07:03,814 Now let’s back to our first case. Here we have 12 PC, and absolutely we will need 12 IP Address. 49 00:07:04,195 --> 00:07:08,307 The question is which prefix is the best for this case? 50 00:07:08,748 --> 00:07:15,174 The answer is very simple, we just need to see in the our calculation before. 51 00:07:15,475 --> 00:07:23,226 Here we have 2 to the power of 1, the result is 2. Absolutely this is not enough for us 52 00:07:23,768 --> 00:07:31,872 4 is also not enough, 8 not enough, and finally, 16 is absolutely enough. 53 00:07:32,551 --> 00:07:37,283 16 is enough for 12 PC. And this is the best. 54 00:07:37,664 --> 00:07:47,442 So which prefix the best? This is easy, the prefix is 32 minus 4. Which is /28. 55 00:07:48,246 --> 00:07:56,307 So in the computer network that consist of 12 PC, the best prefix that we can use is prefix /28. 56 00:07:57,562 --> 00:08:03,834 Okay I hope now you understand how to find the best prefix that we can use in the computer network. 57 00:08:04,123 --> 00:08:10,381 In the next video, we are going to learn another case to find the best prefix we will use. 58 00:08:11,192 --> 00:08:14,537 Thankyou for watching and see you on the next video!