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IPv4 Subnetting Chart

Masks, hosts, subnets and block boundaries. Look up a prefix, or find the block an address falls into, without doing the arithmetic.

Prefix, mask, hosts and subnets

Every prefix from /8 to /32. Hosts is the usable addresses inside one subnet of that size; subnets is how many subnets that prefix carves a class A /8 into.

/Subnet Mask# of Hosts# of Subnets
/8255.0.0.016,777,2141
/9255.128.0.08,388,6060
/10255.192.0.04,194,3022
/11255.224.0.02,097,1506
/12255.240.0.01,048,57414
/13255.248.0.0524,28630
/14255.252.0.0262,14262
/15255.254.0.0131,070126
/16255.255.0.065,534254
/17255.255.128.032,766510
/18255.255.192.016,3821,022
/19255.255.224.08,1902,046
/20255.255.240.04,0944,094
/21255.255.248.02,0468,190
/22255.255.252.01,02216,382
/23255.255.254.051032,766
/24255.255.255.025465,534
/25255.255.255.128126131,070
/26255.255.255.19262262,142
/27255.255.255.22430524,286
/28255.255.255.240141,048,574
/29255.255.255.24862,097,150
/30255.255.255.25224,194,302
/31255.255.255.25408,388,606
/32255.255.255.255016,777,214

2n − 2

One split of a class A /8 per row. Keep n bits for hosts and each subnet holds that many; the 24 − n bits above them give that many subnets.

n# of Hosts# of Subnets
224,194,302
362,097,150
4141,048,574
530524,286
662262,142
7126131,070
825465,534
951032,766
101,02216,382
112,0468,190
124,0944,094
138,1902,046
1416,3821,022
1532,766510
1665,534254
17131,070126
18262,14262
19524,28630
201,048,57414
212,097,1506
224,194,3022
238,388,6060
2416,777,2141

Subnet blocks, by mask octet

Find the octet your mask ends in, then the block your address falls in. The first value of a block is where that subnet starts, the last is where it ends.

.128 blocks of 128 2 blocks prefixes/1/9/17/25
  1. 0-127
  2. 128-255
.192 blocks of 64 4 blocks prefixes/2/10/18/26
  1. 0-63
  2. 64-127
  3. 128-191
  4. 192-255
.224 blocks of 32 8 blocks prefixes/3/11/19/27
  1. 0-31
  2. 32-63
  3. 64-95
  4. 96-127
  5. 128-159
  6. 160-191
  7. 192-223
  8. 224-255
.240 blocks of 16 16 blocks prefixes/4/12/20/28
  1. 0-15
  2. 16-31
  3. 32-47
  4. 48-63
  5. 64-79
  6. 80-95
  7. 96-111
  8. 112-127
  9. 128-143
  10. 144-159
  11. 160-175
  12. 176-191
  13. 192-207
  14. 208-223
  15. 224-239
  16. 240-255
.248 blocks of 8 32 blocks prefixes/5/13/21/29
  1. 0-7
  2. 8-15
  3. 16-23
  4. 24-31
  5. 32-39
  6. 40-47
  7. 48-55
  8. 56-63
  9. 64-71
  10. 72-79
  11. 80-87
  12. 88-95
  13. 96-103
  14. 104-111
  15. 112-119
  16. 120-127
  17. 128-135
  18. 136-143
  19. 144-151
  20. 152-159
  21. 160-167
  22. 168-175
  23. 176-183
  24. 184-191
  25. 192-199
  26. 200-207
  27. 208-215
  28. 216-223
  29. 224-231
  30. 232-239
  31. 240-247
  32. 248-255
.252 blocks of 4 64 blocks prefixes/6/14/22/30
  1. 0-3
  2. 4-7
  3. 8-11
  4. 12-15
  5. 16-19
  6. 20-23
  7. 24-27
  8. 28-31
  9. 32-35
  10. 36-39
  11. 40-43
  12. 44-47
  13. 48-51
  14. 52-55
  15. 56-59
  16. 60-63
  17. 64-67
  18. 68-71
  19. 72-75
  20. 76-79
  21. 80-83
  22. 84-87
  23. 88-91
  24. 92-95
  25. 96-99
  26. 100-103
  27. 104-107
  28. 108-111
  29. 112-115
  30. 116-119
  31. 120-123
  32. 124-127
  33. 128-131
  34. 132-135
  35. 136-139
  36. 140-143
  37. 144-147
  38. 148-151
  39. 152-155
  40. 156-159
  41. 160-163
  42. 164-167
  43. 168-171
  44. 172-175
  45. 176-179
  46. 180-183
  47. 184-187
  48. 188-191
  49. 192-195
  50. 196-199
  51. 200-203
  52. 204-207
  53. 208-211
  54. 212-215
  55. 216-219
  56. 220-223
  57. 224-227
  58. 228-231
  59. 232-235
  60. 236-239
  61. 240-243
  62. 244-247
  63. 248-251
  64. 252-255
.254 blocks of 2 128 blocks prefixes/7/15/23/31
  1. 0-1
  2. 2-3
  3. 4-5
  4. 6-7
  5. 8-9
  6. 10-11
  7. 12-13
  8. 14-15
  9. 16-17
  10. 18-19
  11. 20-21
  12. 22-23
  13. 24-25
  14. 26-27
  15. 28-29
  16. 30-31
  17. 32-33
  18. 34-35
  19. 36-37
  20. 38-39
  21. 40-41
  22. 42-43
  23. 44-45
  24. 46-47
  25. 48-49
  26. 50-51
  27. 52-53
  28. 54-55
  29. 56-57
  30. 58-59
  31. 60-61
  32. 62-63
  33. 64-65
  34. 66-67
  35. 68-69
  36. 70-71
  37. 72-73
  38. 74-75
  39. 76-77
  40. 78-79
  41. 80-81
  42. 82-83
  43. 84-85
  44. 86-87
  45. 88-89
  46. 90-91
  47. 92-93
  48. 94-95
  49. 96-97
  50. 98-99
  51. 100-101
  52. 102-103
  53. 104-105
  54. 106-107
  55. 108-109
  56. 110-111
  57. 112-113
  58. 114-115
  59. 116-117
  60. 118-119
  61. 120-121
  62. 122-123
  63. 124-125
  64. 126-127
  65. 128-129
  66. 130-131
  67. 132-133
  68. 134-135
  69. 136-137
  70. 138-139
  71. 140-141
  72. 142-143
  73. 144-145
  74. 146-147
  75. 148-149
  76. 150-151
  77. 152-153
  78. 154-155
  79. 156-157
  80. 158-159
  81. 160-161
  82. 162-163
  83. 164-165
  84. 166-167
  85. 168-169
  86. 170-171
  87. 172-173
  88. 174-175
  89. 176-177
  90. 178-179
  91. 180-181
  92. 182-183
  93. 184-185
  94. 186-187
  95. 188-189
  96. 190-191
  97. 192-193
  98. 194-195
  99. 196-197
  100. 198-199
  101. 200-201
  102. 202-203
  103. 204-205
  104. 206-207
  105. 208-209
  106. 210-211
  107. 212-213
  108. 214-215
  109. 216-217
  110. 218-219
  111. 220-221
  112. 222-223
  113. 224-225
  114. 226-227
  115. 228-229
  116. 230-231
  117. 232-233
  118. 234-235
  119. 236-237
  120. 238-239
  121. 240-241
  122. 242-243
  123. 244-245
  124. 246-247
  125. 248-249
  126. 250-251
  127. 252-253
  128. 254-255
.255 blocks of 1 256 blocks prefixes/8/16/24/32
  1. 0
  2. 1
  3. 2
  4. 3
  5. 4
  6. 5
  7. 6
  8. 7
  9. 8
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