IPv4 CIDR

Class A, B, C and CIDR networks

Traditionally IP network is classified as A, B or C network. The computers identify the class by first 3 bits (A=000, B=100, C=110), while humans identify the class by first octet(8-bit) number. With scarcity of IP addresses, the class-based system has been replaced by ClasslessInter-DomainRouting (CIDR) to more efficiently allocate IP addresses.

Class Network Address Number of Hosts Netmask
/0 4,294,967,296 0.0.0.0
/1 2,147,483,648 128.0.0.0
/2 1,073,741,824 192.0.0.0
/3 536,870,912 224.0.0.0
/4 240,435,456 240.0.0.0
/5 134,217,728 248.0.0.0
/6 67,108,864 252.0.0.0
/7 33,554,432 254.0.0.0
A /8 16,777,216 255.0.0.0
/9 8,388,608 255.128.0.0
/10 4,194,304 255.192.0.0
/11 2,097,152 255.224.0.0
/12 1,048,576 255.240.0.0
/13 524,288 255.248.0.0
/14 262,144 255.252.0.0
/15 131,072 255.254.0.0
B /16 65,536 255.255.0.0
/17 32,768 255.255.128.0
/18 16,384 255.255.192.0
/19 8,192 255.255.224.0
/20 4,096 255.255.240.0
/21 2,048 255.255.248.0
/22 1,024 255.255.252.0
/23 512 255.255.254.0
C /24 256 255.255.255.0
/25 128 255.255.255.128
/26 64 255.255.255.192
/27 32 255.255.255.224
/28 16 255.255.255.240
/29 8 255.255.255.248
/30 4 255.255.255.252
/31 2 255.255.255.254
/32 1 255.255.255.255

IPv6 CIDR

IPv6 rangeblocks

IPv6 addresses are each 128 bits long. Because each digit in an IPv6 address can have 16 different values (from 0 to 15), each digit represents the overall value of 4 bits (one nibble), with 32 digits total. As with IPv4, CIDR notation describes ranges in terms of a common prefix of bits. For example 2001:db8::/32 means that the range described has the first 32 bits set to the binary digits 00100000000000010000110110101000. Also like IPv4, MediaWiki implements IPv6 rangeblocks using CIDR notation.

  • No organization would ever receive an allocation of this size
  • Regional Internet Registry/very large organization/ISP allocation sizes
  • ISP/large organization allocation sizes
  • Organization allocation sizes
  • End-user allocation sizes
  • Sub-allocations for same enduser
  • (Single address)
CIDR Start of range End of range Total addresses Total /64 subnets
::/0 :: ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff 340,282,366,920,938,463,463,374,607,431,768,211,456 18,446,744,073,709,551,616
::/1 :: 7fff:ffff:ffff:ffff:ffff:ffff:ffff:ffff 170,141,183,460,469,231,731,687,303,715,884,105,728 9,223,372,036,854,775,808
::/2 :: 3fff:ffff:ffff:ffff:ffff:ffff:ffff:ffff 85,070,591,730,234,615,865,843,651,857,942,052,864 4,611,686,018,427,387,904
2000::/3 2000:: 3fff:ffff:ffff:ffff:ffff:ffff:ffff:ffff 42,535,295,865,117,307,932,921,825,928,921,026,432 2,305,843,009,213,693,452
2000::/4 2000:: 2fff:ffff:ffff:ffff:ffff:ffff:ffff:ffff 21,267,647,932,558,653,966,460,912,964,485,513,216 1,152,921,504,606,846,976
2000::/5 2000:: 27ff:ffff:ffff:ffff:ffff:ffff:ffff:ffff 10,633,823,966,279,326,983,230,456,482,242,756,608 576,460,752,303,423,488
2000::/6 2000:: 23ff:ffff:ffff:ffff:ffff:ffff:ffff:ffff 5,316,911,983,139,663,491,615,228,241,121,378,304 288,230,376,151,711,744
2000::/7 2000:: 21ff:ffff:ffff:ffff:ffff:ffff:ffff:ffff 2,658,455,991,569,831,745,807,614,120,560,689,152 144,115,188,075,855,872
2000::/8 2000:: 20ff:ffff:ffff:ffff:ffff:ffff:ffff:ffff 1,329,227,995,784,915,872,903,807,060,280,344,576 72,057,594,037,927,936
2000::/9 2000:: 207f:ffff:ffff:ffff:ffff:ffff:ffff:ffff 664,613,997,892,457,936,451,903,530,140,172,288 36,028,797,018,963,968
2000::/10 2000:: 203f:ffff:ffff:ffff:ffff:ffff:ffff:ffff 332,306,998,946,228,968,225,951,765,070,086,144 18,014,398,509,481,984
2000::/11 2000:: 201f:ffff:ffff:ffff:ffff:ffff:ffff:ffff 166,153,499,473,114,484,112,975,882,535,043,072 9,007,199,254,740,992
2000::/12 2000:: 200f:ffff:ffff:ffff:ffff:ffff:ffff:ffff 83,076,749,736,557,242,056,487,941,267,521,536 4,503,599,627,370,496
2000::/13 2000:: 2007:ffff:ffff:ffff:ffff:ffff:ffff:ffff 41,538,374,868,278,621,028,243,970,633,760,768 2,251,799,813,685,248
2000::/14 2000:: 2003:ffff:ffff:ffff:ffff:ffff:ffff:ffff 20,769,187,434,139,310,514,121,985,316,880,384 1,125,899,906,842,624
2000::/15 2000:: 2001:ffff:ffff:ffff:ffff:ffff:ffff:ffff 10,384,593,717,069,655,257,060,992,658,440,192 562,949,953,421,312
2001::/16 2001:: 2001:ffff:ffff:ffff:ffff:ffff:ffff:ffff 5,192,296,858,534,827,628,530,496,329,220,096 281,474,976,710,656
2001::/17 2001:: 2001:7fff:ffff:ffff:ffff:ffff:ffff:ffff 2,596,148,429,267,413,814,265,248,164,610,048 140,737,488,355,328
2001::/18 2001:: 2001:3fff:ffff:ffff:ffff:ffff:ffff:ffff 1,298,074,214,633,706,907,132,624,082,305,024 70,368,744,177,664
2001::/19 2001:: 2001:1fff:ffff:ffff:ffff:ffff:ffff:ffff 649,037,107,316,853,453,566,312,041,152,512 35,184,372,088,832
2001::/20 2001:: 2001:0fff:ffff:ffff:ffff:ffff:ffff:ffff 324,518,553,658,426,726,783,156,020,576,256 17,592,186,044,416
2001:800::/21 2001:800:: 2001:0fff:ffff:ffff:ffff:ffff:ffff:ffff 162,259,276,829,213,363,391,578,010,288,128 8,796,093,022,208
2001:c00::/22 2001:c00:: 2001:0fff:ffff:ffff:ffff:ffff:ffff:ffff 81,129,638,414,606,681,695,789,005,144,064 4,398,046,511,104
2001:c00::/23 2001:c00:: 2001:0dff:ffff:ffff:ffff:ffff:ffff:ffff 40,564,819,207,303,340,847,894,502,572,032 2,199,023,255,552
2001:d00::/24 2001:d00:: 2001:0dff:ffff:ffff:ffff:ffff:ffff:ffff 20,282,409,603,651,670,423,947,251,286,016 1,099,511,627,776
2001:d80::/25 2001:d80:: 2001:0dff:ffff:ffff:ffff:ffff:ffff:ffff 10,141,204,801,825,835,211,973,625,643,008 549,755,813,888
2001:d80::/26 2001:d80:: 2001:0dbf:ffff:ffff:ffff:ffff:ffff:ffff 5,070,602,400,912,917,605,986,812,821,504 274,877,906,944
2001:da0::/27 2001:da0:: 2001:0dbf:ffff:ffff:ffff:ffff:ffff:ffff 2,535,301,200,456,458,802,993,406,410,752 137,438,953,472
2001:db0::/28 2001:db0:: 2001:0dbf:ffff:ffff:ffff:ffff:ffff:ffff 1,267,650,600,228,229,401,496,703,205,376 68,719,476,736
2001:db8::/29 2001:db8:: 2001:0dbf:ffff:ffff:ffff:ffff:ffff:ffff 633,825,300,114,114,700,748,351,602,688 34,359,738,368
2001:db8::/30 2001:db8:: 2001:0dbb:ffff:ffff:ffff:ffff:ffff:ffff 316,912,650,057,057,350,374,175,801,344 17,179,869,184
2001:db8::/31 2001:db8:: 2001:0db9:ffff:ffff:ffff:ffff:ffff:ffff 158,456,325,028,528,675,187,087,900,672 8,589,934,592
2001:db8::/32 2001:db8:: 2001:db8:ffff:ffff:ffff:ffff:ffff:ffff 79,228,162,514,264,337,593,543,950,336 4,294,967,296
2001:db8::/33 2001:db8:: 2001:db8:7fff:ffff:ffff:ffff:ffff:ffff 39,614,081,257,132,168,796,771,975,168 2,147,483,648
2001:db8::/34 2001:db8:: 2001:db8:3fff:ffff:ffff:ffff:ffff:ffff 19,807,040,628,566,084,398,385,987,584 1,073,741,824
2001:db8::/35 2001:db8:: 2001:db8:1fff:ffff:ffff:ffff:ffff:ffff 9,903,520,314,283,042,199,192,993,792 536,870,912
2001:db8::/36 2001:db8:: 2001:db8:0fff:ffff:ffff:ffff:ffff:ffff 4,951,760,157,141,521,099,596,496,896 268,435,456
2001:db8::/37 2001:db8:: 2001:db8:07ff:ffff:ffff:ffff:ffff:ffff 2,475,880,078,570,760,549,798,248,448 134,217,728
2001:db8::/38 2001:db8:: 2001:db8:03ff:ffff:ffff:ffff:ffff:ffff 1,237,940,039,285,380,274,899,124,224 67,108,864
2001:db8::/39 2001:db8:: 2001:db8:01ff:ffff:ffff:ffff:ffff:ffff 618,970,019,642,690,137,449,562,112 33,554,432
2001:db8::/40 2001:db8:: 2001:db8:00ff:ffff:ffff:ffff:ffff:ffff 309,485,009,821,345,068,724,781,056 16,777,216
2001:db8::/41 2001:db8:: 2001:db8:007f:ffff:ffff:ffff:ffff:ffff 154,742,504,910,672,534,362,390,528 8,388,608
2001:db8::/42 2001:db8:: 2001:db8:003f:ffff:ffff:ffff:ffff:ffff 77,371,252,455,336,267,181,195,264 4,194,304
2001:db8::/43 2001:db8:: 2001:db8:001f:ffff:ffff:ffff:ffff:ffff 38,685,626,227,668,133,590,597,632 2,097,152
2001:db8::/44 2001:db8:: 2001:db8:000f:ffff:ffff:ffff:ffff:ffff 19,342,813,113,834,066,795,298,816 1,048,576
2001:db8::/45 2001:db8:: 2001:db8:0007:ffff:ffff:ffff:ffff:ffff 9,671,406,556,917,033,397,649,408 524,288
2001:db8::/46 2001:db8:: 2001:db8:0003:ffff:ffff:ffff:ffff:ffff 4,835,703,278,458,516,698,824,704 262,144
2001:db8::/47 2001:db8:: 2001:db8:0001:ffff:ffff:ffff:ffff:ffff 2,417,851,639,229,258,349,412,352 131,072
2001:db8::/48 2001:db8:: 2001:db8:0000:ffff:ffff:ffff:ffff:ffff 1,208,925,819,614,629,174,706,176 65,536
2001:db8::/49 2001:db8:: 2001:db8:0000:7fff:ffff:ffff:ffff:ffff 604,462,909,807,314,587,353,088 32,768
2001:db8::/50 2001:db8:: 2001:db8:0000:3fff:ffff:ffff:ffff:ffff 302,231,454,903,657,293,676,544 16,384
2001:db8::/51 2001:db8:: 2001:db8:0000:1fff:ffff:ffff:ffff:ffff 151,115,727,451,828,646,838,272 8,192
2001:db8::/52 2001:db8:: 2001:db8:0000:0fff:ffff:ffff:ffff:ffff 75,557,863,725,914,323,419,136 4,096
2001:db8::/53 2001:db8:: 2001:db8:0000:07ff:ffff:ffff:ffff:ffff 37,778,931,862,957,161,709,568 2,048
2001:db8::/54 2001:db8:: 2001:db8:0000:03ff:ffff:ffff:ffff:ffff 18,889,465,931,478,580,854,784 1,024
2001:db8::/55 2001:db8:: 2001:db8:0000:01ff:ffff:ffff:ffff:ffff 9,444,732,965,739,290,427,392 512
2001:db8::/56 2001:db8:: 2001:db8:0000:00ff:ffff:ffff:ffff:ffff 4,722,366,482,869,645,213,696 256
2001:db8::/57 2001:db8:: 2001:db8:0000:007f:ffff:ffff:ffff:ffff 2,361,183,241,434,822,606,848 128
2001:db8::/58 2001:db8:: 2001:db8:0000:003f:ffff:ffff:ffff:ffff 1,180,591,620,717,411,303,424 64
2001:db8::/59 2001:db8:: 2001:db8:0000:001f:ffff:ffff:ffff:ffff 590,295,810,358,705,651,712 32
2001:db8::/60 2001:db8:: 2001:db8:0000:000f:ffff:ffff:ffff:ffff 295,147,905,179,352,825,856 16
2001:db8::/61 2001:db8:: 2001:db8:0000:0007:ffff:ffff:ffff:ffff 147,573,952,589,676,412,928 8
2001:db8::/62 2001:db8:: 2001:db8:0000:0003:ffff:ffff:ffff:ffff 73,786,976,294,838,206,464 4
2001:db8::/63 2001:db8:: 2001:db8:0000:0001:ffff:ffff:ffff:ffff 36,893,488,147,419,103,232 2
2001:db8::/64 2001:db8:: 2001:db8:0000:0000:ffff:ffff:ffff:ffff 18,446,744,073,709,551,616 1
2001:db8::/65 2001:db8:: 2001:db8:0000:0000:7fff:ffff:ffff:ffff 9,223,372,036,854,775,808 -
2001:db8::/66 2001:db8:: 2001:db8:0000:0000:3fff:ffff:ffff:ffff 4,611,686,018,427,387,904 -
2001:db8::/67 2001:db8:: 2001:db8:0000:0000:1fff:ffff:ffff:ffff 2,305,843,009,213,693,952 -
2001:db8::/68 2001:db8:: 2001:db8:0000:0000:0fff:ffff:ffff:ffff 1,152,921,504,606,846,976 -
2001:db8::/69 2001:db8:: 2001:db8:0000:0000:07ff:ffff:ffff:ffff 576,460,752,303,423,488 -
2001:db8::/70 2001:db8:: 2001:db8:0000:0000:03ff:ffff:ffff:ffff 288,230,376,151,711,744 -
2001:db8::/71 2001:db8:: 2001:db8:0000:0000:01ff:ffff:ffff:ffff 144,115,188,075,855,872 -
2001:db8::/72 2001:db8:: 2001:db8:0000:0000:00ff:ffff:ffff:ffff 72,057,594,037,927,936 -
2001:db8::/73 2001:db8:: 2001:db8:0000:0000:007f:ffff:ffff:ffff 36,028,797,018,963,968 -
2001:db8::/74 2001:db8:: 2001:db8:0000:0000:003f:ffff:ffff:ffff 18,014,398,509,481,984 -
2001:db8::/75 2001:db8:: 2001:db8:0000:0000:001f:ffff:ffff:ffff 9,007,199,254,740,992 -
2001:db8::/76 2001:db8:: 2001:db8:0000:0000:000f:ffff:ffff:ffff 4,503,599,627,370,496 -
2001:db8::/77 2001:db8:: 2001:db8:0000:0000:0007:ffff:ffff:ffff 2,251,799,813,685,248 -
2001:db8::/78 2001:db8:: 2001:db8:0000:0000:0003:ffff:ffff:ffff 1,125,899,906,842,624 -
2001:db8::/79 2001:db8:: 2001:db8:0000:0000:0001:ffff:ffff:ffff 562,949,953,421,312 -
2001:db8::/80 2001:db8:: 2001:db8:0000:0000:0000:ffff:ffff:ffff 281,474,976,710,656 -
2001:db8::/81 2001:db8:: 2001:db8:0000:0000:0000:7fff:ffff:ffff 140,737,488,355,328 -
2001:db8::/82 2001:db8:: 2001:db8:0000:0000:0000:3fff:ffff:ffff 70,368,744,177,664 -
2001:db8::/83 2001:db8:: 2001:db8:0000:0000:0000:1fff:ffff:ffff 35,184,372,088,832 -
2001:db8::/84 2001:db8:: 2001:db8:0000:0000:0000:0fff:ffff:ffff 17,592,186,044,416 -
2001:db8::/85 2001:db8:: 2001:db8:0000:0000:0000:07ff:ffff:ffff 8,796,093,022,208 -
2001:db8::/86 2001:db8:: 2001:db8:0000:0000:0000:03ff:ffff:ffff 4,398,046,511,104 -
2001:db8::/87 2001:db8:: 2001:db8:0000:0000:0000:01ff:ffff:ffff 2,199,023,255,552 -
2001:db8::/88 2001:db8:: 2001:db8:0000:0000:0000:00ff:ffff:ffff 1,099,511,627,776 -
2001:db8::/89 2001:db8:: 2001:db8:0000:0000:0000:007f:ffff:ffff 549,755,813,888 -
2001:db8::/90 2001:db8:: 2001:db8:0000:0000:0000:003f:ffff:ffff 274,877,906,944 -
2001:db8::/91 2001:db8:: 2001:db8:0000:0000:0000:001f:ffff:ffff 137,438,953,472 -
2001:db8::/92 2001:db8:: 2001:db8:0000:0000:0000:000f:ffff:ffff 68,719,476,736 -
2001:db8::/93 2001:db8:: 2001:db8:0000:0000:0000:0007:ffff:ffff 34,359,738,368 -
2001:db8::/94 2001:db8:: 2001:db8:0000:0000:0000:0003:ffff:ffff 17,179,869,184 -
2001:db8::/95 2001:db8:: 2001:db8:0000:0000:0000:0001:ffff:ffff 8,589,934,592 -
2001:db8::/96 2001:db8:: 2001:db8:0000:0000:0000:0000:ffff:ffff 4,294,967,296 -
2001:db8::/97 2001:db8:: 2001:db8:0000:0000:0000:0000:7fff:ffff 2,147,483,648 -
2001:db8::/98 2001:db8:: 2001:db8:0000:0000:0000:0000:3fff:ffff 1,073,741,824 -
2001:db8::/99 2001:db8:: 2001:db8:0000:0000:0000:0000:1fff:ffff 536,870,912 -
2001:db8::/100 2001:db8:: 2001:db8:0000:0000:0000:0000:0fff:ffff 268,435,456 -
2001:db8::/101 2001:db8:: 2001:db8:0000:0000:0000:0000:07ff:ffff 134,217,728 -
2001:db8::/102 2001:db8:: 2001:db8:0000:0000:0000:0000:03ff:ffff 67,108,864 -
2001:db8::/103 2001:db8:: 2001:db8:0000:0000:0000:0000:01ff:ffff 33,554,432 -
2001:db8::/104 2001:db8:: 2001:db8:0000:0000:0000:0000:00ff:ffff 16,777,216 -
2001:db8::/105 2001:db8:: 2001:db8:0000:0000:0000:0000:007f:ffff 8,388,608 -
2001:db8::/106 2001:db8:: 2001:db8:0000:0000:0000:0000:003f:ffff 4,194,304 -
2001:db8::/107 2001:db8:: 2001:db8:0000:0000:0000:0000:001f:ffff 2,097,152 -
2001:db8::/108 2001:db8:: 2001:db8:0000:0000:0000:0000:000f:ffff 1,048,576 -
2001:db8::/109 2001:db8:: 2001:db8:0000:0000:0000:0000:0007:ffff 524,288 -
2001:db8::/110 2001:db8:: 2001:db8:0000:0000:0000:0000:0003:ffff 262,144 -
2001:db8::/111 2001:db8:: 2001:db8:0000:0000:0000:0000:0001:ffff 131,072 -
2001:db8::/112 2001:db8:: 2001:db8:0000:0000:0000:0000:0000:ffff 65,536 -
2001:db8::/113 2001:db8:: 2001:db8:0000:0000:0000:0000:0000:7fff 32,768 -
2001:db8::/114 2001:db8:: 2001:db8:0000:0000:0000:0000:0000:3fff 16,384 -
2001:db8::/115 2001:db8:: 2001:db8:0000:0000:0000:0000:0000:1fff 8,192 -
2001:db8::/116 2001:db8:: 2001:db8:0000:0000:0000:0000:0000:0fff 4,096 -
2001:db8::/117 2001:db8:: 2001:db8:0000:0000:0000:0000:0000:07ff 2,048 -
2001:db8::/118 2001:db8:: 2001:db8:0000:0000:0000:0000:0000:03ff 1,024 -
2001:db8::/119 2001:db8:: 2001:db8:0000:0000:0000:0000:0000:01ff 512 -
2001:db8::/120 2001:db8:: 2001:db8:0000:0000:0000:0000:0000:00ff 256 -
2001:db8::/121 2001:db8:: 2001:db8:0000:0000:0000:0000:0000:007f 128 -
2001:db8::/122 2001:db8:: 2001:db8:0000:0000:0000:0000:0000:003f 64 -
2001:db8::/123 2001:db8:: 2001:db8:0000:0000:0000:0000:0000:001f 32 -
2001:db8::/124 2001:db8:: 2001:db8:0000:0000:0000:0000:0000:000f 16 -
2001:db8::/125 2001:db8:: 2001:db8:0000:0000:0000:0000:0000:0007 8 -
2001:db8::/126 2001:db8:: 2001:db8:0000:0000:0000:0000:0000:0003 4 -
2001:db8::/127 2001:db8:: 2001:db8:0000:0000:0000:0000:0000:0001 2 -
2001:db8::/128 2001:db8:: 2001:db8:: 1 -