I’ve just started learning how to subnet and while there are plenty of resources to help with the calculations and understand the maths I tend to grasp things better if I have some visual representation.
To help, I put together the following table which – I hope – nicely illustrates the patterns of binary 0s and 1s in the 4th octet of a class C IP address and their correlation to the patterns of block sizes, network IDs, host IDs and broadcast addresses of the various subnets. The table is not intended to explain how to calculate subnets nor even to act as a cheat-sheet, but others may find the visual representation helpful.
Some examples of how this table may be useful:
1. Looking in the the 4th Octet of IP Address column and using a CIDR of /27 where only the first 3 bits of the 4th octet of the IP address are used for the network ID the pattern of 0s and 1s starts at 000 for the 1st subnet and then changes 7 times – 001, 010, 011,100, 101, 110 and 111 – each transition marking the beginning of a new subnet.
2. Similarly, the CIDR /27 column shows the 8 subnets each with a block size of 32 and 30 hosts, network IDs of .0, .32, .64, .96, .128, .160, .192 and .224 and broadcast addresses of .31, .63, .95, .127, .159, .191, .223 and .255.
3. Looking in row 125 of the IP # column gives the following for an IP address of 192.168.75.124:
192.168.75.124/25 is the 124th host ID on the 1st subnet that begins with a network ID of 192.168.75.0.
192.168.75.124/26 is the 60th host ID on the 2nd subnet that begins with a network ID of 192.168.75.64.
192.168.75.124/27 is the 28th host ID on the 4th subnet that begins with a network ID of 192.168.75.96.
192.168.75.124/28 is the 12th host ID on the 8th subnet that begins with a network ID of 192.168.75.112.
192.168.75.124/29 is the 4th host ID on the 16th subnet that begins with a network ID of 192.168.75.120.
192.168.75.124/30 is the network ID of the 32nd subnet.
As the table only uses CIDRs /25, /26, /27, /28, /29 and /30 only the first 6 bits of the 4th octet are significant in terms of the network ID. The 7th and 8th bits are used only for the host ID.
Class C Subnets Table
| KEY | Nn | nth Network ID | Bn | nth Broadcast Address | Hn | nth Host of Subnet |
| IP # | 4th Octet Of IP Address | CIDR | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| dec | binary | /25 | /26 | /27 | /28 | /29 | /30 | ||||||||
| 128 (1) | 64 (2) | 32 (3) | 16 (4) | 8 (5) | 4 (6) | 2 (7) | 1 (8) | ||||||||
| 1 | .0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | N1 | N1 | N1 | N1 | N1 | N1 |
| 2 | .1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | H1 | H1 | H1 | H1 | H1 | H1 |
| 3 | .2 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | H2 | H2 | H2 | H2 | H2 | H2 |
| 4 | .3 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 1 | H3 | H3 | H3 | H3 | H3 | B1 |
| 5 | .4 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | H4 | H4 | H4 | H4 | H4 | N2 |
| 6 | .5 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 1 | H5 | H5 | H5 | H5 | H5 | H1 |
| 7 | .6 | 0 | 0 | 0 | 0 | 0 | 1 | 1 | 0 | H6 | H6 | H6 | H6 | H6 | H2 |
| 8 | .7 | 0 | 0 | 0 | 0 | 0 | 1 | 1 | 1 | H7 | H7 | H7 | H7 | B1 | B2 |
| 9 | .8 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 0 | H8 | H8 | H8 | H8 | N2 | N3 |
| 10 | .9 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 1 | H9 | H9 | H9 | H9 | H1 | H1 |
| 11 | .10 | 0 | 0 | 0 | 0 | 1 | 0 | 1 | 0 | H10 | H10 | H10 | H10 | H2 | H2 |
| 12 | .11 | 0 | 0 | 0 | 0 | 1 | 0 | 1 | 1 | H11 | H11 | H11 | H11 | H3 | B3 |
| 13 | .12 | 0 | 0 | 0 | 0 | 1 | 1 | 0 | 0 | H12 | H12 | H12 | H12 | H4 | N4 |
| 14 | .13 | 0 | 0 | 0 | 0 | 1 | 1 | 0 | 1 | H13 | H13 | H13 | H13 | H5 | H1 |
| 15 | .14 | 0 | 0 | 0 | 0 | 1 | 1 | 1 | 0 | H14 | H14 | H14 | H14 | H6 | H2 |
| 16 | .15 | 0 | 0 | 0 | 0 | 1 | 1 | 1 | 1 | H15 | H15 | H15 | B1 | B2 | B4 |
| 17 | .16 | 0 | 0 | 0 | 1 | 0 | 0 | 0 | 0 | H16 | H16 | H16 | N2 | N3 | N5 |
| 18 | .17 | 0 | 0 | 0 | 1 | 0 | 0 | 0 | 1 | H17 | H17 | H17 | H1 | H1 | H1 |
| 19 | .18 | 0 | 0 | 0 | 1 | 0 | 0 | 1 | 0 | H18 | H18 | H18 | H2 | H2 | H2 |
| 20 | .19 | 0 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | H19 | H19 | H19 | H3 | H3 | B5 |
| 21 | .20 | 0 | 0 | 0 | 1 | 0 | 1 | 0 | 0 | H20 | H20 | H20 | H4 | H4 | N6 |
| 22 | .21 | 0 | 0 | 0 | 1 | 0 | 1 | 0 | 1 | H21 | H21 | H21 | H5 | H5 | H1 |
| 23 | .22 | 0 | 0 | 0 | 1 | 0 | 1 | 1 | 0 | H22 | H22 | H22 | H6 | H6 | H2 |
| 24 | .23 | 0 | 0 | 0 | 1 | 0 | 1 | 1 | 1 | H23 | H23 | H23 | H7 | B3 | B6 |
| 25 | .24 | 0 | 0 | 0 | 1 | 1 | 0 | 0 | 0 | H24 | H24 | H24 | H8 | N4 | N7 |
| 26 | .25 | 0 | 0 | 0 | 1 | 1 | 0 | 0 | 1 | H25 | H25 | H25 | H9 | H1 | H1 |
| 27 | .26 | 0 | 0 | 0 | 1 | 1 | 0 | 1 | 0 | H26 | H26 | H26 | H10 | H2 | H2 |
| 28 | .27 | 0 | 0 | 0 | 1 | 1 | 0 | 1 | 1 | H27 | H27 | H27 | H11 | H3 | B7 |
| 29 | .28 | 0 | 0 | 0 | 1 | 1 | 1 | 0 | 0 | H28 | H28 | H28 | H12 | H4 | N8 |
| 30 | .29 | 0 | 0 | 0 | 1 | 1 | 1 | 0 | 1 | H29 | H29 | H29 | H13 | H5 | H1 |
| 31 | .30 | 0 | 0 | 0 | 1 | 1 | 1 | 1 | 0 | H30 | H30 | H30 | H14 | H6 | H2 |
| 32 | .31 | 0 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | H31 | H31 | B1 | B2 | B4 | B8 |
| 33 | .32 | 0 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | H32 | H32 | N2 | N3 | N5 | N9 |
| 34 | .33 | 0 | 0 | 1 | 0 | 0 | 0 | 0 | 1 | H33 | H33 | H1 | H1 | H1 | H1 |
| 35 | .34 | 0 | 0 | 1 | 0 | 0 | 0 | 1 | 0 | H34 | H34 | H2 | H2 | H2 | H2 |
| 36 | .35 | 0 | 0 | 1 | 0 | 0 | 0 | 1 | 1 | H35 | H35 | H3 | H3 | H3 | B9 |
| 37 | .36 | 0 | 0 | 1 | 0 | 0 | 1 | 0 | 0 | H36 | H36 | H4 | H4 | H4 | N10 |
| 38 | .37 | 0 | 0 | 1 | 0 | 0 | 1 | 0 | 1 | H37 | H37 | H5 | H5 | H5 | H1 |
| 39 | .38 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 0 | H38 | H38 | H6 | H6 | H6 | H2 |
| 40 | .39 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 1 | H39 | H39 | H7 | H7 | B5 | B10 |
| 41 | .40 | 0 | 0 | 1 | 0 | 1 | 0 | 0 | 0 | H40 | H40 | H8 | H8 | N6 | N11 |
| 42 | .41 | 0 | 0 | 1 | 0 | 1 | 0 | 0 | 1 | H41 | H41 | H9 | H9 | H1 | H1 |
| 43 | .42 | 0 | 0 | 1 | 0 | 1 | 0 | 1 | 0 | H42 | H42 | H10 | H10 | H2 | H2 |
| 44 | .43 | 0 | 0 | 1 | 0 | 1 | 0 | 1 | 1 | H43 | H43 | H11 | H11 | H3 | B11 |
| 45 | .44 | 0 | 0 | 1 | 0 | 1 | 1 | 0 | 0 | H44 | H44 | H12 | H12 | H4 | N12 |
| 46 | .45 | 0 | 0 | 1 | 0 | 1 | 1 | 0 | 1 | H45 | H45 | H13 | H13 | H5 | H1 |
| 47 | .46 | 0 | 0 | 1 | 0 | 1 | 1 | 1 | 0 | H46 | H46 | H14 | H14 | H6 | H2 |
| 48 | .47 | 0 | 0 | 1 | 0 | 1 | 1 | 1 | 1 | H47 | H47 | H15 | B3 | B6 | B12 |
| 49 | .48 | 0 | 0 | 1 | 1 | 0 | 0 | 0 | 0 | H48 | H48 | H16 | N4 | N7 | N13 |
| 50 | .49 | 0 | 0 | 1 | 1 | 0 | 0 | 0 | 1 | H49 | H49 | H17 | H1 | H1 | H1 |
| 51 | .50 | 0 | 0 | 1 | 1 | 0 | 0 | 1 | 0 | H50 | H50 | H18 | H2 | H2 | H2 |
| 52 | .51 | 0 | 0 | 1 | 1 | 0 | 0 | 1 | 1 | H51 | H51 | H19 | H3 | H3 | B13 |
| 53 | .52 | 0 | 0 | 1 | 1 | 0 | 1 | 0 | 0 | H52 | H52 | H20 | H4 | H4 | N14 |
| 54 | .53 | 0 | 0 | 1 | 1 | 0 | 1 | 0 | 1 | H53 | H53 | H21 | H5 | H5 | H1 |
| 55 | .54 | 0 | 0 | 1 | 1 | 0 | 1 | 1 | 0 | H54 | H54 | H22 | H6 | H6 | H2 |
| 56 | .55 | 0 | 0 | 1 | 1 | 0 | 1 | 1 | 1 | H55 | H55 | H23 | H7 | B7 | B14 |
| 57 | .56 | 0 | 0 | 1 | 1 | 1 | 0 | 0 | 0 | H56 | H56 | H24 | H8 | N8 | N15 |
| 58 | .57 | 0 | 0 | 1 | 1 | 1 | 0 | 0 | 1 | H57 | H57 | H25 | H9 | H1 | H1 |
| 59 | .58 | 0 | 0 | 1 | 1 | 1 | 0 | 1 | 0 | H58 | H58 | H26 | H10 | H2 | H2 |
| 60 | .59 | 0 | 0 | 1 | 1 | 1 | 0 | 1 | 1 | H59 | H59 | H27 | H11 | H3 | B15 |
| 61 | .60 | 0 | 0 | 1 | 1 | 1 | 1 | 0 | 0 | H60 | H60 | H28 | H12 | H4 | N16 |
| 62 | .61 | 0 | 0 | 1 | 1 | 1 | 1 | 0 | 1 | H61 | H61 | H29 | H13 | H5 | H1 |
| 63 | .62 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 0 | H62 | H62 | H30 | H14 | H6 | H2 |
| 64 | .63 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | H63 | B1 | B2 | B4 | B8 | B16 |
| 65 | .64 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | H64 | N2 | N3 | N5 | N9 | N17 |
| 66 | .65 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | 1 | H65 | H1 | H1 | H1 | H1 | H1 |
| 67 | .66 | 0 | 1 | 0 | 0 | 0 | 0 | 1 | 0 | H66 | H2 | H2 | H2 | H2 | H2 |
| 68 | .67 | 0 | 1 | 0 | 0 | 0 | 0 | 1 | 1 | H67 | H3 | H3 | H3 | H3 | B17 |
| 69 | .68 | 0 | 1 | 0 | 0 | 0 | 1 | 0 | 0 | H68 | H4 | H4 | H4 | H4 | N18 |
| 70 | .69 | 0 | 1 | 0 | 0 | 0 | 1 | 0 | 1 | H69 | H5 | H5 | H5 | H5 | H1 |
| 71 | .70 | 0 | 1 | 0 | 0 | 0 | 1 | 1 | 0 | H70 | H6 | H6 | H6 | H6 | H2 |
| 72 | .71 | 0 | 1 | 0 | 0 | 0 | 1 | 1 | 1 | H71 | H7 | H7 | H7 | B9 | B18 |
| 73 | .72 | 0 | 1 | 0 | 0 | 1 | 0 | 0 | 0 | H72 | H8 | H8 | H8 | N10 | N19 |
| 74 | .73 | 0 | 1 | 0 | 0 | 1 | 0 | 0 | 1 | H73 | H9 | H9 | H9 | H1 | H1 |
| 75 | .74 | 0 | 1 | 0 | 0 | 1 | 0 | 1 | 0 | H74 | H10 | H10 | H10 | H2 | H2 |
| 76 | .75 | 0 | 1 | 0 | 0 | 1 | 0 | 1 | 1 | H75 | H11 | H11 | H11 | H3 | B19 |
| 77 | .76 | 0 | 1 | 0 | 0 | 1 | 1 | 0 | 0 | H76 | H12 | H12 | H12 | H4 | N20 |
| 78 | .77 | 0 | 1 | 0 | 0 | 1 | 1 | 0 | 1 | H77 | H13 | H13 | H13 | H5 | H1 |
| 79 | .78 | 0 | 1 | 0 | 0 | 1 | 1 | 1 | 0 | H78 | H14 | H14 | H14 | H6 | H2 |
| 80 | .79 | 0 | 1 | 0 | 0 | 1 | 1 | 1 | 1 | H79 | H15 | H15 | B5 | B10 | B20 |
| 81 | .80 | 0 | 1 | 0 | 1 | 0 | 0 | 0 | 0 | H80 | H16 | H16 | N6 | N11 | N21 |
| 82 | .81 | 0 | 1 | 0 | 1 | 0 | 0 | 0 | 1 | H81 | H17 | H17 | H1 | H1 | H1 |
| 83 | .82 | 0 | 1 | 0 | 1 | 0 | 0 | 1 | 0 | H82 | H18 | H18 | H2 | H2 | H2 |
| 84 | .83 | 0 | 1 | 0 | 1 | 0 | 0 | 1 | 1 | H83 | H19 | H19 | H3 | H3 | B21 |
| 85 | .84 | 0 | 1 | 0 | 1 | 0 | 1 | 0 | 0 | H84 | H20 | H20 | H4 | H4 | N22 |
| 86 | .85 | 0 | 1 | 0 | 1 | 0 | 1 | 0 | 1 | H85 | H21 | H21 | H5 | H5 | H1 |
| 87 | .86 | 0 | 1 | 0 | 1 | 0 | 1 | 1 | 0 | H86 | H22 | H22 | H6 | H6 | H2 |
| 88 | .87 | 0 | 1 | 0 | 1 | 0 | 1 | 1 | 1 | H87 | H23 | H23 | H7 | B11 | B22 |
| 89 | .88 | 0 | 1 | 0 | 1 | 1 | 0 | 0 | 0 | H88 | H24 | H24 | H8 | N12 | N23 |
| 90 | .89 | 0 | 1 | 0 | 1 | 1 | 0 | 0 | 1 | H89 | H25 | H25 | H9 | H1 | H1 |
| 91 | .90 | 0 | 1 | 0 | 1 | 1 | 0 | 1 | 0 | H90 | H26 | H26 | H10 | H2 | H2 |
| 92 | .91 | 0 | 1 | 0 | 1 | 1 | 0 | 1 | 1 | H91 | H27 | H27 | H11 | H3 | B23 |
| 93 | .92 | 0 | 1 | 0 | 1 | 1 | 1 | 0 | 0 | H92 | H28 | H28 | H12 | H4 | N24 |
| 94 | .93 | 0 | 1 | 0 | 1 | 1 | 1 | 0 | 1 | H93 | H29 | H29 | H13 | H5 | H1 |
| 95 | .94 | 0 | 1 | 0 | 1 | 1 | 1 | 1 | 0 | H94 | H30 | H30 | H14 | H6 | H2 |
| 96 | .95 | 0 | 1 | 0 | 1 | 1 | 1 | 1 | 1 | H95 | H31 | B3 | B6 | B12 | B24 |
| 97 | .96 | 0 | 1 | 1 | 0 | 0 | 0 | 0 | 0 | H96 | H32 | N4 | N7 | N13 | N25 |
| 98 | .97 | 0 | 1 | 1 | 0 | 0 | 0 | 0 | 1 | H97 | H33 | H1 | H1 | H1 | H1 |
| 99 | .98 | 0 | 1 | 1 | 0 | 0 | 0 | 1 | 0 | H98 | H34 | H2 | H2 | H2 | H2 |
| 100 | .99 | 0 | 1 | 1 | 0 | 0 | 0 | 1 | 1 | H99 | H35 | H3 | H3 | H3 | B25 |
| 101 | .100 | 0 | 1 | 1 | 0 | 0 | 1 | 0 | 0 | H100 | H36 | H4 | H4 | H4 | N26 |
| 102 | .101 | 0 | 1 | 1 | 0 | 0 | 1 | 0 | 1 | H101 | H37 | H5 | H5 | H5 | H1 |
| 103 | .102 | 0 | 1 | 1 | 0 | 0 | 1 | 1 | 0 | H102 | H38 | H6 | H6 | H6 | H2 |
| 104 | .103 | 0 | 1 | 1 | 0 | 0 | 1 | 1 | 1 | H103 | H39 | H7 | H7 | B13 | B26 |
| 105 | .104 | 0 | 1 | 1 | 0 | 1 | 0 | 0 | 0 | H104 | H40 | H8 | H8 | N14 | N27 |
| 106 | .105 | 0 | 1 | 1 | 0 | 1 | 0 | 0 | 1 | H105 | H41 | H9 | H9 | H1 | H1 |
| 107 | .106 | 0 | 1 | 1 | 0 | 1 | 0 | 1 | 0 | H106 | H42 | H10 | H10 | H2 | H2 |
| 108 | .107 | 0 | 1 | 1 | 0 | 1 | 0 | 1 | 1 | H107 | H43 | H11 | H11 | H3 | B27 |
| 109 | .108 | 0 | 1 | 1 | 0 | 1 | 1 | 0 | 0 | H108 | H44 | H12 | H12 | H4 | N28 |
| 110 | .109 | 0 | 1 | 1 | 0 | 1 | 1 | 0 | 1 | H109 | H45 | H13 | H13 | H5 | H1 |
| 111 | .110 | 0 | 1 | 1 | 0 | 1 | 1 | 1 | 0 | H110 | H46 | H14 | H14 | H6 | H2 |
| 112 | .111 | 0 | 1 | 1 | 0 | 1 | 1 | 1 | 1 | H111 | H47 | H15 | B7 | B14 | B28 |
| 113 | .112 | 0 | 1 | 1 | 1 | 0 | 0 | 0 | 0 | H112 | H48 | H16 | N8 | N15 | N29 |
| 114 | .113 | 0 | 1 | 1 | 1 | 0 | 0 | 0 | 1 | H113 | H49 | H17 | H1 | H1 | H1 |
| 115 | .114 | 0 | 1 | 1 | 1 | 0 | 0 | 1 | 0 | H114 | H50 | H18 | H2 | H2 | H2 |
| 116 | .115 | 0 | 1 | 1 | 1 | 0 | 0 | 1 | 1 | H115 | H51 | H19 | H3 | H3 | B29 |
| 117 | .116 | 0 | 1 | 1 | 1 | 0 | 1 | 0 | 0 | H116 | H52 | H20 | H4 | H4 | N30 |
| 118 | .117 | 0 | 1 | 1 | 1 | 0 | 1 | 0 | 1 | H117 | H53 | H21 | H5 | H5 | H1 |
| 119 | .118 | 0 | 1 | 1 | 1 | 0 | 1 | 1 | 0 | H118 | H54 | H22 | H6 | H6 | H2 |
| 120 | .119 | 0 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | H119 | H55 | H23 | H7 | B15 | B30 |
| 121 | .120 | 0 | 1 | 1 | 1 | 1 | 0 | 0 | 0 | H120 | H56 | H24 | H8 | N16 | N31 |
| 122 | .121 | 0 | 1 | 1 | 1 | 1 | 0 | 0 | 1 | H121 | H57 | H25 | H9 | H1 | H1 |
| 123 | .122 | 0 | 1 | 1 | 1 | 1 | 0 | 1 | 0 | H122 | H58 | H26 | H10 | H2 | H2 |
| 124 | .123 | 0 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | H123 | H59 | H27 | H11 | H3 | B31 |
| 125 | .124 | 0 | 1 | 1 | 1 | 1 | 1 | 0 | 0 | H124 | H60 | H28 | H12 | H4 | N32 |
| 126 | .125 | 0 | 1 | 1 | 1 | 1 | 1 | 0 | 1 | H125 | H61 | H29 | H13 | H5 | H1 |
| 127 | .126 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 0 | H126 | H62 | H30 | H14 | H6 | H2 |
| 128 | .127 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | B1 | B2 | B4 | B8 | B16 | B32 |
| 129 | .128 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | N2 | N3 | N5 | N9 | N17 | N33 |
| 130 | .129 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | H1 | H1 | H1 | H1 | H1 | H1 |
| 131 | .130 | 1 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | H2 | H2 | H2 | H2 | H2 | H2 |
| 132 | .131 | 1 | 0 | 0 | 0 | 0 | 0 | 1 | 1 | H3 | H3 | H3 | H3 | H3 | B33 |
| 133 | .132 | 1 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | H4 | H4 | H4 | H4 | H4 | N34 |
| 134 | .133 | 1 | 0 | 0 | 0 | 0 | 1 | 0 | 1 | H5 | H5 | H5 | H5 | H5 | H1 |
| 135 | .134 | 1 | 0 | 0 | 0 | 0 | 1 | 1 | 0 | H6 | H6 | H6 | H6 | H6 | H2 |
| 136 | .135 | 1 | 0 | 0 | 0 | 0 | 1 | 1 | 1 | H7 | H7 | H7 | H7 | B17 | B34 |
| 137 | .136 | 1 | 0 | 0 | 0 | 1 | 0 | 0 | 0 | H8 | H8 | H8 | H8 | N18 | N35 |
| 138 | .137 | 1 | 0 | 0 | 0 | 1 | 0 | 0 | 1 | H9 | H9 | H9 | H9 | H1 | H1 |
| 139 | .138 | 1 | 0 | 0 | 0 | 1 | 0 | 1 | 0 | H10 | H10 | H10 | H10 | H2 | H2 |
| 140 | .139 | 1 | 0 | 0 | 0 | 1 | 0 | 1 | 1 | H11 | H11 | H11 | H11 | H3 | B35 |
| 141 | .140 | 1 | 0 | 0 | 0 | 1 | 1 | 0 | 0 | H12 | H12 | H12 | H12 | H4 | N36 |
| 142 | .141 | 1 | 0 | 0 | 0 | 1 | 1 | 0 | 1 | H13 | H13 | H13 | H13 | H5 | H1 |
| 143 | .142 | 1 | 0 | 0 | 0 | 1 | 1 | 1 | 0 | H14 | H14 | H14 | H14 | H6 | H2 |
| 144 | .143 | 1 | 0 | 0 | 0 | 1 | 1 | 1 | 1 | H15 | H15 | H15 | B9 | B18 | B36 |
| 145 | .144 | 1 | 0 | 0 | 1 | 0 | 0 | 0 | 0 | H16 | H16 | H16 | N10 | N19 | N37 |
| 146 | .145 | 1 | 0 | 0 | 1 | 0 | 0 | 0 | 1 | H17 | H17 | H17 | H1 | H1 | H1 |
| 147 | .146 | 1 | 0 | 0 | 1 | 0 | 0 | 1 | 0 | H18 | H18 | H18 | H2 | H2 | H2 |
| 148 | .147 | 1 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | H19 | H19 | H19 | H3 | H3 | B37 |
| 149 | .148 | 1 | 0 | 0 | 1 | 0 | 1 | 0 | 0 | H20 | H20 | H20 | H4 | H4 | N38 |
| 150 | .149 | 1 | 0 | 0 | 1 | 0 | 1 | 0 | 1 | H21 | H21 | H21 | H5 | H5 | H1 |
| 151 | .150 | 1 | 0 | 0 | 1 | 0 | 1 | 1 | 0 | H22 | H22 | H22 | H6 | H6 | H2 |
| 152 | .151 | 1 | 0 | 0 | 1 | 0 | 1 | 1 | 1 | H23 | H23 | H23 | H7 | B19 | B38 |
| 153 | .152 | 1 | 0 | 0 | 1 | 1 | 0 | 0 | 0 | H24 | H24 | H24 | H8 | N20 | N39 |
| 154 | .153 | 1 | 0 | 0 | 1 | 1 | 0 | 0 | 1 | H25 | H25 | H25 | H9 | H1 | H1 |
| 155 | .154 | 1 | 0 | 0 | 1 | 1 | 0 | 1 | 0 | H26 | H26 | H26 | H10 | H2 | H2 |
| 156 | .155 | 1 | 0 | 0 | 1 | 1 | 0 | 1 | 1 | H27 | H27 | H27 | H11 | H3 | B39 |
| 157 | .156 | 1 | 0 | 0 | 1 | 1 | 1 | 0 | 0 | H28 | H28 | H28 | H12 | H4 | N40 |
| 158 | .157 | 1 | 0 | 0 | 1 | 1 | 1 | 0 | 1 | H29 | H29 | H29 | H13 | H5 | H1 |
| 159 | .158 | 1 | 0 | 0 | 1 | 1 | 1 | 1 | 0 | H30 | H30 | H30 | H14 | H6 | H2 |
| 160 | .159 | 1 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | H31 | H31 | B5 | B10 | B20 | B40 |
| 161 | .160 | 1 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | H32 | H32 | N6 | N11 | N21 | N41 |
| 162 | .161 | 1 | 0 | 1 | 0 | 0 | 0 | 0 | 1 | H33 | H33 | H1 | H1 | H1 | H1 |
| 163 | .162 | 1 | 0 | 1 | 0 | 0 | 0 | 1 | 0 | H34 | H34 | H2 | H2 | H2 | H2 |
| 164 | .163 | 1 | 0 | 1 | 0 | 0 | 0 | 1 | 1 | H35 | H35 | H3 | H3 | H3 | B41 |
| 165 | .164 | 1 | 0 | 1 | 0 | 0 | 1 | 0 | 0 | H36 | H36 | H4 | H4 | H4 | N42 |
| 166 | .165 | 1 | 0 | 1 | 0 | 0 | 1 | 0 | 1 | H37 | H37 | H5 | H5 | H5 | H1 |
| 167 | .166 | 1 | 0 | 1 | 0 | 0 | 1 | 1 | 0 | H38 | H38 | H6 | H6 | H6 | H2 |
| 168 | .167 | 1 | 0 | 1 | 0 | 0 | 1 | 1 | 1 | H39 | H39 | H7 | H7 | B21 | B42 |
| 169 | .168 | 1 | 0 | 1 | 0 | 1 | 0 | 0 | 0 | H40 | H40 | H8 | H8 | N22 | N43 |
| 170 | .169 | 1 | 0 | 1 | 0 | 1 | 0 | 0 | 1 | H41 | H41 | H9 | H9 | H1 | H1 |
| 171 | .170 | 1 | 0 | 1 | 0 | 1 | 0 | 1 | 0 | H42 | H42 | H10 | H10 | H2 | H2 |
| 172 | .171 | 1 | 0 | 1 | 0 | 1 | 0 | 1 | 1 | H43 | H43 | H11 | H11 | H3 | B43 |
| 173 | .172 | 1 | 0 | 1 | 0 | 1 | 1 | 0 | 0 | H44 | H44 | H12 | H12 | H4 | N44 |
| 174 | .173 | 1 | 0 | 1 | 0 | 1 | 1 | 0 | 1 | H45 | H45 | H13 | H13 | H5 | H1 |
| 175 | .174 | 1 | 0 | 1 | 0 | 1 | 1 | 1 | 0 | H46 | H46 | H14 | H14 | H6 | H2 |
| 176 | .175 | 1 | 0 | 1 | 0 | 1 | 1 | 1 | 1 | H47 | H47 | H15 | B11 | B22 | B44 |
| 177 | .176 | 1 | 0 | 1 | 1 | 0 | 0 | 0 | 0 | H48 | H48 | H16 | N12 | N23 | N45 |
| 178 | .177 | 1 | 0 | 1 | 1 | 0 | 0 | 0 | 1 | H49 | H49 | H17 | H1 | H1 | H1 |
| 179 | .178 | 1 | 0 | 1 | 1 | 0 | 0 | 1 | 0 | H50 | H50 | H18 | H2 | H2 | H2 |
| 180 | .179 | 1 | 0 | 1 | 1 | 0 | 0 | 1 | 1 | H51 | H51 | H19 | H3 | H3 | B45 |
| 181 | .180 | 1 | 0 | 1 | 1 | 0 | 1 | 0 | 0 | H52 | H52 | H20 | H4 | H4 | N46 |
| 182 | .181 | 1 | 0 | 1 | 1 | 0 | 1 | 0 | 1 | H53 | H53 | H21 | H5 | H5 | H1 |
| 183 | .182 | 1 | 0 | 1 | 1 | 0 | 1 | 1 | 0 | H54 | H54 | H22 | H6 | H6 | H2 |
| 184 | .183 | 1 | 0 | 1 | 1 | 0 | 1 | 1 | 1 | H55 | H55 | H23 | H7 | B23 | B46 |
| 185 | .184 | 1 | 0 | 1 | 1 | 1 | 0 | 0 | 0 | H56 | H56 | H24 | H8 | N24 | N47 |
| 186 | .185 | 1 | 0 | 1 | 1 | 1 | 0 | 0 | 1 | H57 | H57 | H25 | H9 | H1 | H1 |
| 187 | .186 | 1 | 0 | 1 | 1 | 1 | 0 | 1 | 0 | H58 | H58 | H26 | H10 | H2 | H2 |
| 188 | .187 | 1 | 0 | 1 | 1 | 1 | 0 | 1 | 1 | H59 | H59 | H27 | H11 | H3 | B47 |
| 189 | .188 | 1 | 0 | 1 | 1 | 1 | 1 | 0 | 0 | H60 | H60 | H28 | H12 | H4 | N48 |
| 190 | .189 | 1 | 0 | 1 | 1 | 1 | 1 | 0 | 1 | H61 | H61 | H29 | H13 | H5 | H1 |
| 191 | .190 | 1 | 0 | 1 | 1 | 1 | 1 | 1 | 0 | H62 | H62 | H30 | H14 | H6 | H2 |
| 192 | .191 | 1 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | H63 | B3 | B6 | B12 | B24 | B48 |
| 193 | .192 | 1 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | H64 | N4 | N7 | N13 | N25 | N49 |
| 194 | .193 | 1 | 1 | 0 | 0 | 0 | 0 | 0 | 1 | H65 | H1 | H1 | H1 | H1 | H1 |
| 195 | .194 | 1 | 1 | 0 | 0 | 0 | 0 | 1 | 0 | H66 | H2 | H2 | H2 | H2 | H2 |
| 196 | .195 | 1 | 1 | 0 | 0 | 0 | 0 | 1 | 1 | H67 | H3 | H3 | H3 | H3 | B49 |
| 197 | .196 | 1 | 1 | 0 | 0 | 0 | 1 | 0 | 0 | H68 | H4 | H4 | H4 | H4 | N50 |
| 198 | .197 | 1 | 1 | 0 | 0 | 0 | 1 | 0 | 1 | H69 | H5 | H5 | H5 | H5 | H1 |
| 199 | .198 | 1 | 1 | 0 | 0 | 0 | 1 | 1 | 0 | H70 | H6 | H6 | H6 | H6 | H2 |
| 200 | .199 | 1 | 1 | 0 | 0 | 0 | 1 | 1 | 1 | H71 | H7 | H7 | H7 | B25 | B50 |
| 201 | .200 | 1 | 1 | 0 | 0 | 1 | 0 | 0 | 0 | H72 | H8 | H8 | H8 | N26 | N51 |
| 202 | .201 | 1 | 1 | 0 | 0 | 1 | 0 | 0 | 1 | H73 | H9 | H9 | H9 | H1 | H1 |
| 203 | .202 | 1 | 1 | 0 | 0 | 1 | 0 | 1 | 0 | H74 | H10 | H10 | H10 | H2 | H2 |
| 204 | .203 | 1 | 1 | 0 | 0 | 1 | 0 | 1 | 1 | H75 | H11 | H11 | H11 | H3 | B51 |
| 205 | .204 | 1 | 1 | 0 | 0 | 1 | 1 | 0 | 0 | H76 | H12 | H12 | H12 | H4 | N52 |
| 206 | .205 | 1 | 1 | 0 | 0 | 1 | 1 | 0 | 1 | H77 | H13 | H13 | H13 | H5 | H1 |
| 207 | .206 | 1 | 1 | 0 | 0 | 1 | 1 | 1 | 0 | H78 | H14 | H14 | H14 | H6 | H2 |
| 208 | .207 | 1 | 1 | 0 | 0 | 1 | 1 | 1 | 1 | H79 | H15 | H15 | B13 | B26 | B52 |
| 209 | .208 | 1 | 1 | 0 | 1 | 0 | 0 | 0 | 0 | H80 | H16 | H16 | N14 | N27 | N53 |
| 210 | .209 | 1 | 1 | 0 | 1 | 0 | 0 | 0 | 1 | H81 | H17 | H17 | H1 | H1 | H1 |
| 211 | .210 | 1 | 1 | 0 | 1 | 0 | 0 | 1 | 0 | H82 | H18 | H18 | H2 | H2 | H2 |
| 212 | .211 | 1 | 1 | 0 | 1 | 0 | 0 | 1 | 1 | H83 | H19 | H19 | H3 | H3 | B53 |
| 213 | .212 | 1 | 1 | 0 | 1 | 0 | 1 | 0 | 0 | H84 | H20 | H20 | H4 | H4 | N54 |
| 214 | .213 | 1 | 1 | 0 | 1 | 0 | 1 | 0 | 1 | H85 | H21 | H21 | H5 | H5 | H1 |
| 215 | .214 | 1 | 1 | 0 | 1 | 0 | 1 | 1 | 0 | H86 | H22 | H22 | H6 | H6 | H2 |
| 216 | .215 | 1 | 1 | 0 | 1 | 0 | 1 | 1 | 1 | H87 | H23 | H23 | H7 | B27 | B54 |
| 217 | .216 | 1 | 1 | 0 | 1 | 1 | 0 | 0 | 0 | H88 | H24 | H24 | H8 | N28 | N55 |
| 218 | .217 | 1 | 1 | 0 | 1 | 1 | 0 | 0 | 1 | H89 | H25 | H25 | H9 | H1 | H1 |
| 219 | .218 | 1 | 1 | 0 | 1 | 1 | 0 | 1 | 0 | H90 | H26 | H26 | H10 | H2 | H2 |
| 220 | .219 | 1 | 1 | 0 | 1 | 1 | 0 | 1 | 1 | H91 | H27 | H27 | H11 | H3 | B55 |
| 221 | .220 | 1 | 1 | 0 | 1 | 1 | 1 | 0 | 0 | H92 | H28 | H28 | H12 | H4 | N56 |
| 222 | .221 | 1 | 1 | 0 | 1 | 1 | 1 | 0 | 1 | H93 | H29 | H29 | H13 | H5 | H1 |
| 223 | .222 | 1 | 1 | 0 | 1 | 1 | 1 | 1 | 0 | H94 | H30 | H30 | H14 | H6 | H2 |
| 224 | .223 | 1 | 1 | 0 | 1 | 1 | 1 | 1 | 1 | H95 | H31 | B7 | B14 | B28 | B56 |
| 225 | .224 | 1 | 1 | 1 | 0 | 0 | 0 | 0 | 0 | H96 | H32 | N8 | N15 | N29 | N57 |
| 226 | .225 | 1 | 1 | 1 | 0 | 0 | 0 | 0 | 1 | H97 | H33 | H1 | H1 | H1 | H1 |
| 227 | .226 | 1 | 1 | 1 | 0 | 0 | 0 | 1 | 0 | H98 | H34 | H2 | H2 | H2 | H2 |
| 228 | .227 | 1 | 1 | 1 | 0 | 0 | 0 | 1 | 1 | H99 | H35 | H3 | H3 | H3 | B57 |
| 229 | .228 | 1 | 1 | 1 | 0 | 0 | 1 | 0 | 0 | H100 | H36 | H4 | H4 | H4 | N58 |
| 230 | .229 | 1 | 1 | 1 | 0 | 0 | 1 | 0 | 1 | H101 | H37 | H5 | H5 | H5 | H1 |
| 231 | .230 | 1 | 1 | 1 | 0 | 0 | 1 | 1 | 0 | H102 | H38 | H6 | H6 | H6 | H2 |
| 232 | .231 | 1 | 1 | 1 | 0 | 0 | 1 | 1 | 1 | H103 | H39 | H7 | H7 | B29 | B58 |
| 233 | .232 | 1 | 1 | 1 | 0 | 1 | 0 | 0 | 0 | H104 | H40 | H8 | H8 | N30 | N59 |
| 234 | .233 | 1 | 1 | 1 | 0 | 1 | 0 | 0 | 1 | H105 | H41 | H9 | H9 | H1 | H1 |
| 235 | .234 | 1 | 1 | 1 | 0 | 1 | 0 | 1 | 0 | H106 | H42 | H10 | H10 | H2 | H2 |
| 236 | .235 | 1 | 1 | 1 | 0 | 1 | 0 | 1 | 1 | H107 | H43 | H11 | H11 | H3 | B59 |
| 237 | .236 | 1 | 1 | 1 | 0 | 1 | 1 | 0 | 0 | H108 | H44 | H12 | H12 | H4 | N60 |
| 238 | .237 | 1 | 1 | 1 | 0 | 1 | 1 | 0 | 1 | H109 | H45 | H13 | H13 | H5 | H1 |
| 239 | .238 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 0 | H110 | H46 | H14 | H14 | H6 | H2 |
| 240 | .239 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 1 | H111 | H47 | H15 | B15 | B30 | B60 |
| 241 | .240 | 1 | 1 | 1 | 1 | 0 | 0 | 0 | 0 | H112 | H48 | H16 | N16 | N31 | N61 |
| 242 | .241 | 1 | 1 | 1 | 1 | 0 | 0 | 0 | 1 | H113 | H49 | H17 | H1 | H1 | H1 |
| 243 | .242 | 1 | 1 | 1 | 1 | 0 | 0 | 1 | 0 | H114 | H50 | H18 | H2 | H2 | H2 |
| 244 | .243 | 1 | 1 | 1 | 1 | 0 | 0 | 1 | 1 | H115 | H51 | H19 | H3 | H3 | B61 |
| 245 | .244 | 1 | 1 | 1 | 1 | 0 | 1 | 0 | 0 | H116 | H52 | H20 | H4 | H4 | N62 |
| 246 | .245 | 1 | 1 | 1 | 1 | 0 | 1 | 0 | 1 | H117 | H53 | H21 | H5 | H5 | H1 |
| 247 | .246 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 0 | H118 | H54 | H22 | H6 | H6 | H2 |
| 248 | .247 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | H119 | H55 | H23 | H7 | B31 | B62 |
| 249 | .248 | 1 | 1 | 1 | 1 | 1 | 0 | 0 | 0 | H120 | H56 | H24 | H8 | N32 | N63 |
| 250 | .249 | 1 | 1 | 1 | 1 | 1 | 0 | 0 | 1 | H121 | H57 | H25 | H9 | H1 | H1 |
| 251 | .250 | 1 | 1 | 1 | 1 | 1 | 0 | 1 | 0 | H122 | H58 | H26 | H10 | H2 | H2 |
| 252 | .251 | 1 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | H123 | H59 | H27 | H11 | H3 | B63 |
| 253 | .252 | 1 | 1 | 1 | 1 | 1 | 1 | 0 | 0 | H124 | H60 | H28 | H12 | H4 | N64 |
| 254 | .253 | 1 | 1 | 1 | 1 | 1 | 1 | 0 | 1 | H125 | H61 | H29 | H13 | H5 | H1 |
| 255 | .254 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 0 | H126 | H62 | H30 | H14 | H6 | H2 |
| 256 | .255 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | B2 | B4 | B8 | B16 | B32 | B64 |
| KEY | Nn | nth Network ID | Bn | nth Broadcast Address | Hn | nth Host of Subnet |
Summary of Class C Subnets Table
| CIDR | Masked Bits [1s] (x) | Unmasked Bits [0s] (y) | Mask [4th Octet] | Block Size1 [256 – Mask] | # Subnets [2x] | # Hosts Per Subnet2 [2y – 2] |
|---|---|---|---|---|---|---|
| 25 | 1 | 7 | .128 | 128 | 2 | 126 |
| 26 | 2 | 6 | .192 | 64 | 4 | 62 |
| 27 | 3 | 5 | .224 | 32 | 8 | 30 |
| 28 | 4 | 4 | .240 | 16 | 16 | 14 |
| 29 | 5 | 3 | .248 | 8 | 32 | 6 |
| 30 | 6 | 2 | .252 | 4 | 64 | 2 |
1 Block Size can also be calculated as 2y
2 # Hosts Per Subnet can also be calculated as Block Size – 2
