1 00:00:00,240 --> 00:00:03,790 Here are the requirements starting with the network. 2 00:00:03,810 --> 00:00:08,640 One seven, two point sixteen Dot 1.0 slash 24. 3 00:00:09,210 --> 00:00:20,100 I need to subnet this network into one two three four five six seven subnets. 4 00:00:20,970 --> 00:00:23,850 The requirements for each subnet are listed. 5 00:00:24,180 --> 00:00:26,130 125 hosts over here. 6 00:00:27,030 --> 00:00:30,990 59 hosts over here between the routers. 7 00:00:31,260 --> 00:00:35,040 Two hosts, each coming off the router. 8 00:00:35,040 --> 00:00:37,500 That's the edge router that connects to the internet. 9 00:00:37,770 --> 00:00:46,230 We have a DMZ which needs 25 hosts and coming off of the router here, we need a 12 hosts network for 10 00:00:46,230 --> 00:00:50,370 management when creating subnets. 11 00:00:50,490 --> 00:00:57,990 We have to remember that the sizes of subnets that we can create are constrained by the binary place 12 00:00:57,990 --> 00:00:58,680 values. 13 00:00:59,160 --> 00:01:09,060 The binary place values, if you look at eight bits, are 128, 64, 32, 16, eight, four, two and 14 00:01:09,060 --> 00:01:09,480 one. 15 00:01:10,230 --> 00:01:19,170 In other words, we cannot create a subnet specifically for 125 hosts, but we can create a subnet for 16 00:01:19,170 --> 00:01:26,130 128 hosts, two of which are not usable, so it would be effectively 126 hosts. 17 00:01:26,820 --> 00:01:27,690 In other words? 18 00:01:28,760 --> 00:01:35,420 We can create subnets for one hundred and twenty eight minus two hosts, which meets the requirement 19 00:01:35,600 --> 00:01:37,190 of 125 hosts. 20 00:01:37,730 --> 00:01:46,970 Similarly, instead of 59 hosts, we can create a subnet for 64 minus two hosts, meaning 62 usable 21 00:01:46,970 --> 00:01:47,570 hosts. 22 00:01:48,800 --> 00:01:56,960 For the management network, instead of 12, host will create a subnet for 16 minus two hosts or 14 23 00:01:56,960 --> 00:01:57,890 usable hosts. 24 00:01:58,900 --> 00:02:07,450 For the point to point networks of two hosts, each will use the place value of four to create four 25 00:02:07,660 --> 00:02:17,980 minus two usable hosts per subnet and for the DMZ network will create a subnet of 30 to minus two or 26 00:02:17,980 --> 00:02:19,480 30 usable hosts. 27 00:02:19,990 --> 00:02:24,430 This will meet the requirement of 25 hosts for the DMZ. 28 00:02:25,740 --> 00:02:33,780 So now that we know the sizes of the subnets will need to create, we need to ask ourself if the network 29 00:02:33,780 --> 00:02:39,930 that we're starting with has enough address space to accommodate these networks. 30 00:02:40,940 --> 00:02:50,240 Currently, the one seven two six one zero network is slashed 24, meaning it's a 256 hosts network 31 00:02:50,450 --> 00:02:55,250 or 256 minus two, is 254 usable hosts. 32 00:02:56,150 --> 00:03:06,830 If we add 120 eight plus 64 plus 32 plus 16, we get 240. 33 00:03:07,890 --> 00:03:11,070 Add four, eight and 12 more. 34 00:03:11,430 --> 00:03:20,610 We get two hundred and fifty to two hundred and fifty two hosts is less than 256, so we should have 35 00:03:20,610 --> 00:03:29,580 enough address space in the one seven two six one 1.0 network to accommodate these seven subnets. 36 00:03:31,540 --> 00:03:37,420 So now that we figured out the different sizes of subnets that we're going to need to create, I have 37 00:03:37,420 --> 00:03:46,450 listed them out here working from largest to smallest and starting with the one seven two six one zero 38 00:03:46,450 --> 00:03:46,960 subnet. 39 00:03:47,410 --> 00:03:50,680 The question is what will the subnet mask be? 40 00:03:51,670 --> 00:04:01,600 Currently, the subnet mask is slashed 24 to create a subnet for 128 minus two hosts will need to borrow 41 00:04:01,750 --> 00:04:02,680 one bit. 42 00:04:03,340 --> 00:04:06,490 The 128 bit in the binary place values. 43 00:04:06,970 --> 00:04:11,980 This will create a subnet mask of twenty five ones. 44 00:04:11,980 --> 00:04:16,150 You can see the one bit here in the one hundred and twenty eighth place. 45 00:04:16,630 --> 00:04:26,470 This is a slash 25 subnet mask, so I'll put in twenty five here and you can see that we now have a 46 00:04:26,480 --> 00:04:29,290 Slash 25 subnet mask. 47 00:04:29,590 --> 00:04:34,930 This creates 128 minus two usable hosts for two reasons. 48 00:04:35,140 --> 00:04:41,200 The first reason is the last one is our subnet multiplier and the subnet multiplier. 49 00:04:41,200 --> 00:04:44,170 The one here is in the 128th place. 50 00:04:44,470 --> 00:04:48,850 This means that the networks will go up by 128. 51 00:04:49,390 --> 00:04:58,210 Also, the zeros that are left over in the host portion are seven zeros and two to the seventh power 52 00:04:58,420 --> 00:04:59,800 is 128. 53 00:05:00,070 --> 00:05:08,860 In other words, we have 128 values in the host bits minus two makes 126 usable hosts. 54 00:05:11,940 --> 00:05:21,360 So the one seven two six one zero gets a slash 25 subnet mask, creating a network that goes from zero 55 00:05:21,510 --> 00:05:22,890 to 127. 56 00:05:23,130 --> 00:05:26,570 And the next network will start at one hundred and twenty eight. 57 00:05:27,860 --> 00:05:36,380 Now, how many bits do we need to borrow from the host portion to create a subnet starting at 128 for 58 00:05:36,380 --> 00:05:39,290 64 minus two usable hosts? 59 00:05:40,690 --> 00:05:47,740 To create this subnet will need to borrow two bits from the host portion of the subnet mask. 60 00:05:48,100 --> 00:05:59,440 Notice that now we have a slash 26 subnet mask because there's 26 ones and the subnet multiplier is 61 00:05:59,440 --> 00:06:01,300 in the 64s place. 62 00:06:02,800 --> 00:06:10,570 We have six zeros in the host bits, meaning two to the sixth power is 64. 63 00:06:10,930 --> 00:06:15,040 So we have 64 minus two usable hosts. 64 00:06:16,390 --> 00:06:22,120 With the subnet multiplier in the 64s place, the sublets now go up by 64. 65 00:06:22,510 --> 00:06:28,060 So the next subnet will be one hundred and ninety two. 66 00:06:29,790 --> 00:06:38,190 With the next subnet, starting at 192 to create a subnet for 32 minus two usable hosts will need to 67 00:06:38,190 --> 00:06:47,250 have the subnet mask and at the 32s place, the subnet mask will now look like this. 68 00:06:47,550 --> 00:06:53,460 You can see we have 27 ones to make a slash 27 subnet mask. 69 00:06:53,880 --> 00:07:01,800 The last one in the subnet mask, the subnet multiplier is in the 32s place, so the networks will now 70 00:07:01,800 --> 00:07:03,570 go up by 30 to. 71 00:07:05,720 --> 00:07:08,960 Slash, 27, is now our subnet mask. 72 00:07:10,040 --> 00:07:20,000 The networks will go up by 32, so starting at 192, the next network will be two 24. 73 00:07:21,520 --> 00:07:30,670 To create the next subnet of 16 minus two usable hosts will need to change the subnet mask to slash 74 00:07:30,670 --> 00:07:31,360 tape. 75 00:07:31,720 --> 00:07:38,890 Now I'm borrowing one two three four bits from the host portion of the subnet mask. 76 00:07:39,460 --> 00:07:45,310 I've got four zeros or two to the fourth power creating 16 hosts. 77 00:07:46,720 --> 00:07:52,690 The subnet multiplier is in the 16's place, meaning the networks will go up by 16. 78 00:07:53,200 --> 00:08:00,160 So we now have a slash 28 subnet mask with 28 ones. 79 00:08:00,880 --> 00:08:03,430 The networks now go up by 16. 80 00:08:03,670 --> 00:08:07,600 So the next network will start at two 40. 81 00:08:11,330 --> 00:08:18,260 For the final three, subnets will change the subnet mask to slash 30. 82 00:08:18,960 --> 00:08:28,100 Now we're borrowing six bits from the host portion of the original subnet mask for host bits. 83 00:08:28,130 --> 00:08:36,830 We only have two zeroes or four values in the host portion of the subnet mask, creating four minus 84 00:08:36,830 --> 00:08:44,470 two or two usable hosts per subnet with the subnet mask at EGX30. 85 00:08:45,110 --> 00:08:47,690 The subnet multiplier being in the first place. 86 00:08:47,960 --> 00:08:49,910 The network's go up by four. 87 00:08:50,480 --> 00:08:53,600 So we now have the 240. 88 00:08:55,940 --> 00:09:09,380 To 44 and to 48 subnet notice that 240 has four hosts, two usable hosts, the next subnet starts at 89 00:09:09,380 --> 00:09:14,210 244 and the following subnet starts at 248. 90 00:09:15,140 --> 00:09:20,870 These subnets are now all slash 30. 91 00:09:24,710 --> 00:09:28,880 We can clearly see that with a slash 25 subnet mask. 92 00:09:29,270 --> 00:09:37,100 We have a subnet multiplier of 128 and we have 128 minus two usable hosts. 93 00:09:37,400 --> 00:09:42,320 The next network starts at 128 with the 128 network. 94 00:09:42,590 --> 00:09:44,810 We have a slash 26 subnet mask. 95 00:09:45,230 --> 00:09:47,480 The subnet multiplier 64. 96 00:09:47,900 --> 00:09:50,630 So the next network starts at 192. 97 00:09:51,290 --> 00:09:58,280 The 192 network has a 27 subnet mask with the subnet multiplier in the 32s place. 98 00:09:58,700 --> 00:10:01,580 So the next network starts at 224. 99 00:10:02,390 --> 00:10:08,750 The 224 Subnet has a 28 subnet mask with a slash 20 subnet mask. 100 00:10:09,110 --> 00:10:15,620 The subnet multiplier is in the 16's place, making the next network start at 240. 101 00:10:15,980 --> 00:10:17,990 It goes up by 16. 102 00:10:18,830 --> 00:10:26,810 The 240 subnet has a 30 subnet mask, which is in the Ford's place, or the subnet multiplier being 103 00:10:26,810 --> 00:10:27,500 a four. 104 00:10:27,770 --> 00:10:34,550 And the network now goes up by for the 02:44 network also has a slash 30. 105 00:10:34,790 --> 00:10:36,980 So the network goes up by four. 106 00:10:37,160 --> 00:10:48,620 And so the last network is a 248 network slash 30, meaning the subnet is size four or four hosts two 107 00:10:48,620 --> 00:10:49,310 usable. 108 00:10:49,640 --> 00:10:58,130 If you do not count the network and broadcast address, we now have all of our subnets noticed there's 109 00:10:58,130 --> 00:11:00,410 no overlapping address spaces. 110 00:11:00,890 --> 00:11:04,550 The first subnet goes from zero to 127. 111 00:11:05,060 --> 00:11:09,200 The next subnet goes from 128 to 191. 112 00:11:10,280 --> 00:11:10,640 Next. 113 00:11:10,670 --> 00:11:16,130 Network 192 goes from 192 to 223. 114 00:11:16,790 --> 00:11:23,840 And you can see that none of the address spaces overlap and the subnet mask is sized for that particular 115 00:11:23,840 --> 00:11:24,350 subnet. 116 00:11:25,130 --> 00:11:31,790 I can now go and put all of the subnets into their proper places within the topology.