Internet Protocol version 6 (IPv6) is the latest version of the Internet Protocol (IP), the communications protocol that provides an identification and location system for computers on networks and routes traffic across the Internet. IPv6 was developed by the Internet Engineering Task Force (IETF) to deal with the long-anticipated problem of IPv4 address exhaustion. IPv6 is intended to replace IPv4.
IPv6 Subnet Size Reference Table
| IPv6 CIDR Subnet | Number of IPs |
| /128 | 1 |
| /127 | 2 |
| /126 | 4 |
| /125 | 8 |
| /124 | 16 |
| /123 | 32 |
| /122 | 64 |
| /121 | 128 |
| /120 | 256 |
| /119 | 512 |
| /118 | 1,024 |
| /117 | 2,048 |
| /116 | 4,096 |
| /115 | 8,192 |
| /114 | 16,384 |
| /113 | 32,768 |
| /112 | 65,536 |
| /111 | 131,072 |
| /110 | 262,144 |
| /109 | 524,288 |
| /108 | 1,048,576 |
| /107 | 2,097,152 |
| /106 | 4,194,304 |
| /105 | 8,388,608 |
| /104 | 16,777,216 |
| /103 | 33,554,432 |
| /102 | 67,108,864 |
| /101 | 134,217,728 |
| /100 | 268,435,456 |
| /99 | 536,870,912 |
| /98 | 1,073,741,824 |
| /97 | 2,147,483,648 |
| /96 | 4,294,967,296 |
| /95 | 8,589,934,592 |
| /94 | 17,179,869,184 |
| /93 | 34,359,738,368 |
| /92 | 68,719,476,736 |
| /91 | 137,438,953,472 |
| /90 | 274,877,906,944 |
| /89 | 549,755,813,888 |
| /88 | 1,099,511,627,776 |
| /87 | 2,199,023,255,552 |
| /86 | 4,398,046,511,104 |
| /85 | 8,796,093,022,208 |
| /84 | 17,592,186,044,416 |
| /83 | 35,184,372,088,832 |
| /82 | 70,368,744,177,664 |
| /81 | 140,737,488,355,328 |
| /80 | 281,474,976,710,656 |
| /79 | 562,949,953,421,312 |
| /78 | 1,125,899,906,842,624 |
| /77 | 2,251,799,813,685,248 |
| /76 | 4,503,599,627,370,496 |
| /75 | 9,007,199,254,740,992 |
| /74 | 18,014,398,509,481,985 |
| /73 | 36,028,797,018,963,968 |
| /72 | 72,057,594,037,927,936 |
| /71 | 144,115,188,075,855,872 |
| /70 | 288,230,376,151,711,744 |
| /69 | 576,460,752,303,423,488 |
| /68 | 1,152,921,504,606,846,976 |
| /67 | 2,305,843,009,213,693,952 |
| /66 | 4,611,686,018,427,387,904 |
| /65 | 9,223,372,036,854,775,808 |
| Residential – /64 | 18,446,744,073,709,551,616 |
| /63 | 36,893,488,147,419,103,232 |
| /62 | 73,786,976,294,838,206,464 |
| /61 | 147,573,952,589,676,412,928 |
| /60 | 295,147,905,179,352,825,856 |
| /59 | 590,295,810,358,705,651,712 |
| /58 | 1,180,591,620,717,411,303,424 |
| /57 | 2,361,183,241,434,822,606,848 |
| /56 | 4,722,366,482,869,645,213,696 |
| /55 | 9,444,732,965,739,290,427,392 |
| /54 | 18,889,465,931,478,580,854,784 |
| /53 | 37,778,931,862,957,161,709,568 |
| /52 | 75,557,863,725,914,323,419,136 |
| /51 | 151,115,727,451,828,646,838,272 |
| /50 | 302,231,454,903,657,293,676,544 |
| /49 | 604,462,909,807,314,587,353,088 |
| Business – /48 | 1,208,925,819,614,629,174,706,176 |
| /47 | 2,417,851,639,229,258,349,412,352 |
| /46 | 4,835,703,278,458,516,698,824,704 |
| /45 | 9,671,406,556,917,033,397,649,408 |
| /44 | 19,342,813,113,834,066,795,298,816 |
| /43 | 38,685,626,227,668,133,590,597,632 |
| /42 | 77,371,252,455,336,267,181,195,264 |
| /41 | 154,742,504,910,672,534,362,390,528 |
| /40 | 309,485,009,821,345,068,724,781,056 |
| /39 | 618,970,019,642,690,137,449,562,112 |
| /38 | 1,237,940,039,285,380,274,899,124,224 |
| /37 | 2,475,880,078,570,760,549,798,248,448 |
| /36 | 4,951,760,157,141,521,099,596,496,896 |
| /35 | 9,903,520,314,283,042,199,192,993,792 |
| /34 | 19,807,040,628,566,084,398,385,987,584 |
| /33 | 39,614,081,257,132,168,796,771,975,168 |
| ISP – /32 | 79,228,162,514,264,337,593,543,950,336 |
| /31 | 158,456,325,028,528,675,187,087,900,672 |
| /30 | 316,912,650,057,057,350,374,175,801,344 |
| /29 | 633,825,300,114,114,700,748,351,602,688 |
| /28 | 1,267,650,600,228,229,401,496,703,205,376 |
| /27 | 2,535,301,200,456,458,802,993,406,410,752 |
| /26 | 5,070,602,400,912,917,605,986,812,821,504 |
| /25 | 10,141,204,801,825,835,211,973,625,643,008 |
| /24 | 20,282,409,603,651,670,423,947,251,286,016 |
| /23 | 40,564,819,207,303,340,847,894,502,572,032 |
| /22 | 81,129,638,414,606,681,695,789,005,144,064 |
| /21 | 162,259,276,829,213,363,391,578,010,288,128 |
| /20 | 324,518,553,658,426,726,783,156,020,576,256 |
| /19 | 649,037,107,316,853,453,566,312,041,152,512 |
| /18 | 1,298,074,214,633,706,907,132,624,082,305,024 |
| /17 | 2,596,148,429,267,413,814,265,248,164,610,048 |
| /16 | 5,192,296,858,534,827,628,530,496,329,220,096 |
| /15 | 10,384,593,717,069,655,257,060,992,658,440,192 |
| /14 | 20,769,187,434,139,310,514,121,985,316,880,384 |
| /13 | 41,538,374,868,278,621,028,243,970,633,760,768 |
| /12 | 83,076,749,736,557,242,056,487,941,267,521,536 |
| /11 | 166,153,499,473,114,484,112,975,882,535,043,072 |
| /10 | 332,306,998,946,228,968,225,951,765,070,086,144 |
| /9 | 664,613,997,892,457,936,451,903,530,140,172,288 |
| /8 | 1,329,227,995,784,915,872,903,807,060,280,344,576 |
IPv6 Subnet Reference Prefix Lengths
2001:0DB8:0000:0000:0000:0000:0000:0001
XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX
||| |||| |||| |||| |||| |||| ||||
||| |||| |||| |||| |||| |||| |||128
||| |||| |||| |||| |||| |||| ||124
||| |||| |||| |||| |||| |||| |120
||| |||| |||| |||| |||| |||| 116
||| |||| |||| |||| |||| |||112
||| |||| |||| |||| |||| ||108
||| |||| |||| |||| |||| |104
||| |||| |||| |||| |||| 100
||| |||| |||| |||| |||96
||| |||| |||| |||| ||92
||| |||| |||| |||| |88
||| |||| |||| |||| 84
||| |||| |||| |||80
||| |||| |||| ||76
||| |||| |||| |72
||| |||| |||| 68
||| |||| |||64
||| |||| ||60
||| |||| |56
||| |||| 52
||| |||48
||| ||44
||| |40
||| 36
||32
|28
24
Example of /48 Allocations
/48 allocations are usually provided to business, who require additional VLANs or may require the range to be split up. Using a /48 allocation would allow them to do so.
2001:0DB8:0000::/48
2001:0DB8:0001::/48
2001:0DB8:0002::/48
2001:0DB8:0003::/48
2001:0DB8:0004::/48
2001:0DB8:0005::/48
2001:0DB8:0006::/48
2001:0DB8:0007::/48
2001:0DB8:0008::/48
2001:0DB8:0009::/48
2001:0DB8:000A::/48
2001:0DB8:000B::/48
2001:0DB8:000C::/48
2001:0DB8:000D::/48
2001:0DB8:000E::/48
2001:0DB8:000F::/48
2001:0DB8:0010::/48
2001:0DB8:0011::/48
Example of /64 Allocations
/64 IPv6 allocations are usually given to end users, who do not require any VLANs. It allows auto configuration, or SLAAC so makes life a lot easier when configuring. It is fairly easy to calculate /64 allocations, and a subnet calculator is not required. In fact this is the case with assigning IPv6 allocations, it can be done fairly easily without any calculator:
2001:0DB8:0010:0000::/64
2001:0DB8:0010:0001::/64
2001:0DB8:0010:0002::/64
2001:0DB8:0010:0003::/64
2001:0DB8:0010:0004::/64
2001:0DB8:0010:0005::/64
2001:0DB8:0010:0006::/64
2001:0DB8:0010:0007::/64
2001:0DB8:0010:0008::/64
2001:0DB8:0010:0009::/64
2001:0DB8:0010:000A::/64
2001:0DB8:0010:000B::/64
2001:0DB8:0010:000C::/64
2001:0DB8:0010:000D::/64
2001:0DB8:0010:000E::/64
2001:0DB8:0010:000F::/64
2001:0DB8:0010:0010::/64
2001:0DB8:0010:0011::/64
IPv6 Subnet Calculator
In most cases a subnet calculator will not be required, since IPv6 using hex (hexadecimal) – and so long as the prefix length is a multiple of 4, it makes it quite easy. For example (this is also where the table “IPv6 Subnet Reference IP Address” comes in handy above):
2001:DB8:1234:1234::/64
2001:DB8:1234:123X::/60
2001:DB8:1234:12XX::/56
2001:DB8:1234:1XXX::/52
2001:DB8:1234:XXXX::/48
2001:DB8:123X:XXXX::/44
2001:DB8:12XX:XXXX::/40
IPv6 Address Scopes
::/0 – default route
::/128 – unspecified address
::1/128 – localhost
fe80::/10 – link local
fc00::/7 – unique local unicast (RFC 4193)
fc00::/8 – centrally assigned by unknown, routed within a site (RFC 4193)
fd00::/8 – free for all, global ID must be generated randomly with pseudo-random algorithm, routed within a site (RFC 4193)
ff00::/8 – multicast, following after the prefix ff there are 4 bits for flags and 4 bits for the scope
::ffff:0:0/96 – IPv4 to IPv6 Address, eg: ::ffff:10.10.10.10 (RFC 4038)
2000::/3 – global unicast
2001::/16 /32 – subnets assigned to providers, they assign /48, /56 or /64 to the customer
2001:db8::/32 – reserved for use in documentation
2001:678::/29 – Provider Independent (PI) addresses and anycasting TLD name servers
2002::/16 – 6to4 scope, 2002:c058:6301:: is the 6to4 public router anycast (RFC 3068)