1 00:00:00,440 --> 00:00:05,595 In the previous video, we already learn how to find the best prefix we can use in the 2 00:00:05,595 --> 00:00:06,631 computer network. 3 00:00:07,377 --> 00:00:14,051 Here we have 100 computers, and we know from the previous video that the best prefix for 4 00:00:14,051 --> 00:00:17,177 100 computers is /25. 5 00:00:18,092 --> 00:00:23,486 Now, in this video, we are going to determine which IP Address we will use. 6 00:00:24,473 --> 00:00:30,126 In the previous video, I also already tell you about Public and Private IP Address. 7 00:00:30,500 --> 00:00:36,232 And we need to remember that we must use Private IP Address in the local network. 8 00:00:36,798 --> 00:00:41,925 Here is the range of Private IP Address, we are free to use which range. 9 00:00:42,346 --> 00:00:50,890 we can use 10, or 172.16 or 192.168, we can use whatever we want. 10 00:00:51,371 --> 00:00:55,933 In this case, I want to use 192.168.0.0. 11 00:00:56,571 --> 00:01:01,086 This IP is included in the third range of Private IP Address. 12 00:01:01,868 --> 00:01:05,918 Now, remember that we need to pay attention on the last number. 13 00:01:06,351 --> 00:01:09,676 The first third number will never change. 14 00:01:09,976 --> 00:01:12,664 But the last number will be change. 15 00:01:13,254 --> 00:01:18,773 If you remember, the number of IP Address is between 0 until 255. 16 00:01:19,411 --> 00:01:25,120 So the last number have a chance to change become 0 until 255. 17 00:01:26,239 --> 00:01:28,218 Okay let’s start learning. 18 00:01:28,928 --> 00:01:31,807 In this case we will search for several thing. 19 00:01:31,987 --> 00:01:38,882 Which is Total IP, Subnetmask, IP Network, IP Broadcast, and IP Range. 20 00:01:39,604 --> 00:01:42,337 We will learn about all of this one by one. 21 00:01:42,914 --> 00:01:45,508 First let’s search for the total IP. 22 00:01:45,869 --> 00:01:53,563 We already learn about this, to find the total IP is 2 to the power of 32 minus prefix, 23 00:01:53,876 --> 00:02:04,622 in this case, the prefix is /25, 32 minus 25 is 7, and 2 to the power of 7 is 128. 24 00:02:05,332 --> 00:02:09,822 So the total IP for prefix /25 is 128. 25 00:02:10,869 --> 00:02:16,697 If you forget about the powers, I recommend you to always write it, so 2 to the power 26 00:02:16,697 --> 00:02:19,568 of 1 until 2 to the power of 8. 27 00:02:20,266 --> 00:02:25,203 Later, if you get used to this, you will never need to write the powers again. 28 00:02:26,009 --> 00:02:30,433 You will able to calculate subnetting without even writing anything. 29 00:02:31,179 --> 00:02:36,256 So don’t worry to write everything if you just start learning about computer network. 30 00:02:37,242 --> 00:02:43,488 Okay, now we know that the total IP for prefix /25 is 128. 31 00:02:44,065 --> 00:02:46,948 Next we are going to find the subnetmask. 32 00:02:47,321 --> 00:02:51,732 But before that, we will learn about what is subnetmask first. 33 00:02:52,237 --> 00:02:56,215 Actually, the function of subnetmask is same as prefix. 34 00:02:56,853 --> 00:03:04,267 Some vendor will need prefix when configure an IP Address, but some vendor will need subnetmask. 35 00:03:06,168 --> 00:03:08,192 Let’s say we have mikrotik. 36 00:03:09,467 --> 00:03:13,772 In Mikrotik we will need prefix when configuring IP Address. 37 00:03:14,229 --> 00:03:21,000 But in cisco, we don’t need prefix, we need subnetmask when configuring IP Address. 38 00:03:21,881 --> 00:03:30,659 Another example, in windows, we need subnetmask, but in linux, some times we will use prefix 39 00:03:30,659 --> 00:03:32,383 rather than subnetmask. 40 00:03:32,805 --> 00:03:36,154 But some time we also use subnetmask in linux. 41 00:03:36,768 --> 00:03:41,217 The point is, that the function of subnetmask is same as prefix. 42 00:03:41,530 --> 00:03:46,319 Some vendor using prefix, but some vendor using subnetmask. 43 00:03:46,848 --> 00:03:49,382 Now let’s see in cisco packet tracer. 44 00:03:49,791 --> 00:03:54,690 In the previous video, we already build a simple computer network like this. 45 00:03:55,171 --> 00:03:57,925 Let’s take a look again to the PC 0. 46 00:03:58,334 --> 00:04:01,706 Go to desktop and then IP Configuration. 47 00:04:02,801 --> 00:04:07,718 Here we can see that when we configure an IP Address, we will also need to configure 48 00:04:07,718 --> 00:04:08,874 subnetmask. 49 00:04:09,440 --> 00:04:16,699 But here we don’t see any field to put prefix. So in this case, we will need subnetmask instead 50 00:04:16,699 --> 00:04:18,149 of prefix. 51 00:04:19,124 --> 00:04:22,383 Okay, now you understand what is subnetmask. 52 00:04:22,684 --> 00:04:27,000 Next, let’s calculate subnetmask for prefix /25. 53 00:04:27,633 --> 00:04:32,069 The formula is 256 minus by Total IP. 54 00:04:34,355 --> 00:04:37,961 In this case, the total IP is 128. 55 00:04:38,851 --> 00:04:46,007 So 256 minus 128, the answer is 128. 56 00:04:46,922 --> 00:04:54,000 If we see in the cisco packet tracer again, the subnetmask is contains of 4 part of numbers. 57 00:04:54,391 --> 00:05:00,161 In this case the subnetmask is 255.255.255.0. 58 00:05:00,823 --> 00:05:07,077 Well for prefix /25, we already find that the subnetmask is 128. 59 00:05:07,583 --> 00:05:11,911 This 128 is used in the last number of subnetmask. 60 00:05:12,693 --> 00:05:20,666 So the subnetmask for prefix /25 is 255.255.255.128. 61 00:05:21,809 --> 00:05:26,342 Okay now I hope you understand how to calculate total IP and subnetmask. 62 00:05:26,751 --> 00:05:32,271 In the next video, we are going to learn about Network IP, Broadcast IP, and IP Range. 63 00:05:32,849 --> 00:05:35,662 Thankyou for watching and see you on the next video!