IPv6

1.0 Format

IPv6 is an identifier with a fixed length of 128-bit¹ (2¹²⁸), which can represent more than 340 short-scale undecillion² different values. This is a decimal number with 39 digits:

340 282 366 920 938 463 463 374 607 431 768 211 456

In contrast to the dot-decimal notation used in IPv4, which has four decimal 8-bit groups, IPv6 uses a colon-hexadecimal notation which has eight hexadecimal groups where each has 16 bit:

2001:0DB8:7654:0010:FEDC:0000:0000:3210

A hexadecimal number can reflect 16 (2⁴) different values (0-9, A-F) which corresponds to exactly 4 bit. Since every group consists of four hexadecimal numbers, each group has 16 bit (2¹⁶):

2001:0DB8:7654:0010:

FEDC:0000:0000:3210

IPv6 addresses are separated into two 64-bit parts, where the first on the left is the subnet prefix and the second on the right is the interface identifier (IID), which is a modified 64-Bit Extended Unique Identifier (EUI-64):

2001:0DB8:7654:0010:FEDC:0000:0000:3210

Example for often used ranges:

2001:0DB8:7654:0010:

Interface Identifier

FEDC:0000:0000:3210

2.0 Compressed Format

Leading zeros in a group can be omitted as long the group would not end up empty:

2001:0DB8:0000:0010:FEDC:0000:0000:3210

► Result:

2001:DB8:0:10:FEDC:0:0:3210

Additionally, one or more groups only containing zeros (0 or 0000) can be replaced with a double colon (::). However, this can be done only once per address, so one would usually choose the series with the most subsequent zero groups. In our example, that will be the red series:

2001:DB8:0:10:FEDC:0:0:3210

► Result:

2001:DB8:0:10:FEDC::3210

3.0 CIDR Tables

3.1 /128 to /64

(In 4-bit steps)

- Prefix
- IP Addresses
- Prefix Address

- /128³
- 1
- 0
- ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff
- /124
- 16
- 0
- ffff:ffff:ffff:ffff:ffff:ffff:ffff:fff0
- /120
- 256
- 0
- ffff:ffff:ffff:ffff:ffff:ffff:ffff:ff00
- /116
- 4 096
- 0
- ffff:ffff:ffff:ffff:ffff:ffff:ffff:f000
- /112
- 65 536
- 0
- ffff:ffff:ffff:ffff:ffff:ffff:ffff:0
- /108
- 1 048 576
- 0
- ffff:ffff:ffff:ffff:ffff:ffff:fff0:0
- /104
- 16 777 216
- 0
- ffff:ffff:ffff:ffff:ffff:ffff:ff00:0
- /100
- 268 435 456
- 0
- ffff:ffff:ffff:ffff:ffff:ffff:f000:0
- /96
- 4 294 967 296
- 1
- ffff:ffff:ffff:ffff:ffff:ffff:0:0
- /92
- 68 719 476 736
- 16
- ffff:ffff:ffff:ffff:ffff:fff0:0:0
- /88
- 1 099 511 627 776
- 256
- ffff:ffff:ffff:ffff:ffff:ff00:0:0
- /84
- 17 592 186 044 416
- 4 096
- ffff:ffff:ffff:ffff:ffff:f000:0:0
- /80
- 281 474 976 710 656
- 65 536
- ffff:ffff:ffff:ffff:ffff:0:0:0
- /76
- 4 503 599 627 370 496
- 1 048 576
- ffff:ffff:ffff:ffff:fff0:0:0:0
- /72
- 72 057 594 037 927 936
- 16 777 216
- ffff:ffff:ffff:ffff:ff00:0:0:0
- /68
- 1 152 921 504 606 846 976
- 268 435 456
- ffff:ffff:ffff:ffff:f000:0:0:0
- /64⁴
- 18 446 744 073 709 551 616
- 4 294 967 296
- ffff:ffff:ffff:ffff:0:0:0:0

3.2 /63 to /32

- Prefix
- /56s
- /48s
- /36s
- Prefix Address

- /63
- 2
- 0
- 0
- 0
- ffff:ffff:ffff:fffe:0:0:0:0
- /62
- 4
- 0
- 0
- 0
- ffff:ffff:ffff:fffc:0:0:0:0
- /61
- 8
- 0
- 0
- 0
- ffff:ffff:ffff:fff8:0:0:0:0
- /60
- 16
- 0
- 0
- 0
- ffff:ffff:ffff:fff0:0:0:0:0
- /59
- 32
- 0
- 0
- 0
- ffff:ffff:ffff:ffe0:0:0:0:0
- /58
- 64
- 0
- 0
- 0
- ffff:ffff:ffff:ffc0:0:0:0:0
- /57
- 128
- 0
- 0
- 0
- ffff:ffff:ffff:ff80:0:0:0:0
- /56⁵
- 256
- 1
- 0
- 0
- ffff:ffff:ffff:ff00:0:0:0:0
- /55
- 512
- 2
- 0
- 0
- ffff:ffff:ffff:fe00:0:0:0:0
- /54
- 1 024
- 4
- 0
- 0
- ffff:ffff:ffff:fc00:0:0:0:0
- /53
- 2 048
- 8
- 0
- 0
- ffff:ffff:ffff:f800:0:0:0:0
- /52
- 4 096
- 16
- 0
- 0
- ffff:ffff:ffff:f000:0:0:0:0
- /51
- 8 192
- 32
- 0
- 0
- ffff:ffff:ffff:e000:0:0:0:0
- /50
- 16 384
- 64
- 0
- 0
- ffff:ffff:ffff:c000:0:0:0:0
- /49
- 32 768
- 128
- 0
- 0
- ffff:ffff:ffff:8000:0:0:0:0
- /48⁶
- 65 536
- 256
- 1
- 0
- ffff:ffff:ffff:0:0:0:0:0
- /47
- 131 072
- 512
- 2
- 0
- ffff:ffff:fffe:0:0:0:0:0
- /46
- 262 144
- 1 024
- 4
- 0
- ffff:ffff:fffc:0:0:0:0:0
- /45
- 524 288
- 2 048
- 8
- 0
- ffff:ffff:fff8:0:0:0:0:0
- /44
- 1 048 576
- 4 096
- 16
- 0
- ffff:ffff:fff0:0:0:0:0:0
- /43
- 2 097 152
- 8 192
- 32
- 0
- ffff:ffff:ffe0:0:0:0:0:0
- /42
- 4 194 304
- 16 384
- 64
- 0
- ffff:ffff:ffc0:0:0:0:0:0
- /41
- 8 388 608
- 32 768
- 128
- 0
- ffff:ffff:ff80:0:0:0:0:0
- /40
- 16 777 216
- 65 536
- 256
- 0
- ffff:ffff:ff00:0:0:0:0:0
- /39
- 33 554 432
- 131 072
- 512
- 0
- ffff:ffff:fe00:0:0:0:0:0
- /38
- 67 108 864
- 262 144
- 1 024
- 0
- ffff:ffff:fc00:0:0:0:0:0
- /37
- 134 217 728
- 524 288
- 2 048
- 0
- ffff:ffff:f800:0:0:0:0:0
- /36
- 268 435 456
- 1 048 576
- 4 096
- 1
- ffff:ffff:f000:0:0:0:0:0
- /35
- 536 870 912
- 2 097 152
- 8 192
- 2
- ffff:ffff:e000:0:0:0:0:0
- /34
- 1 073 741 824
- 4 194 304
- 16 384
- 4
- ffff:ffff:c000:0:0:0:0:0
- /33
- 2 147 483 648
- 8 388 608
- 32 768
- 8
- ffff:ffff:8000:0:0:0:0:0
- /32⁷
- 4 294 967 296
- 16 777 216
- 65 536
- 16
- ffff:ffff:0:0:0:0:0:0

3.3 /31 to /0

- Prefix
- /23s
- /16s
- /12s
- Prefix Address

- /31
- 2
- 0
- 0
- 0
- ffff:fffe:0:0:0:0:0:0
- /30
- 4
- 0
- 0
- 0
- ffff:fffc:0:0:0:0:0:0
- /29⁸
- 8
- 0
- 0
- 0
- ffff:fff8:0:0:0:0:0:0
- /28
- 16
- 0
- 0
- 0
- ffff:fff0:0:0:0:0:0:0
- /27
- 32
- 0
- 0
- 0
- ffff:ffe0:0:0:0:0:0:0
- /26
- 64
- 0
- 0
- 0
- ffff:ffc0:0:0:0:0:0:0
- /25
- 128
- 0
- 0
- 0
- ffff:ff80:0:0:0:0:0:0
- /24
- 256
- 0
- 0
- 0
- ffff:ff00:0:0:0:0:0:0
- /23⁹
- 512
- 1
- 0
- 0
- ffff:fe00:0:0:0:0:0:0
- /22
- 1 024
- 2
- 0
- 0
- ffff:fc00:0:0:0:0:0:0
- /21
- 2 048
- 4
- 0
- 0
- ffff:f800:0:0:0:0:0:0
- /20
- 4 096
- 8
- 0
- 0
- ffff:f000:0:0:0:0:0:0
- /19
- 8 192
- 16
- 0
- 0
- ffff:e000:0:0:0:0:0:0
- /18
- 16 384
- 32
- 0
- 0
- ffff:c000:0:0:0:0:0:0
- /17
- 32 768
- 64
- 0
- 0
- ffff:8000:0:0:0:0:0:0
- /16
- 65 536
- 128
- 1
- 0
- ffff:0:0:0:0:0:0:0
- /15
- 131 072
- 256
- 2
- 0
- fffe:0:0:0:0:0:0:0
- /14
- 262 144
- 512
- 4
- 0
- fffc:0:0:0:0:0:0:0
- /13
- 524 288
- 1 024
- 8
- 0
- fff8:0:0:0:0:0:0:0
- /12¹⁰
- 1 048 576
- 2 048
- 16
- 1
- fff0:0:0:0:0:0:0:0
- /11
- 2 097 152
- 4 096
- 32
- 2
- ffe0:0:0:0:0:0:0:0
- /10
- 4 194 304
- 8 192
- 64
- 4
- ffc0:0:0:0:0:0:0:0
- /9
- 8 388 608
- 16 384
- 128
- 8
- ff80:0:0:0:0:0:0:0
- /8
- 16 777 216
- 32 768
- 256
- 16
- ff00:0:0:0:0:0:0:0
- /7
- 33 554 432
- 65 536
- 512
- 32
- fe00:0:0:0:0:0:0:0
- /6
- 67 108 864
- 131 072
- 1 024
- 64
- fc00:0:0:0:0:0:0:0
- /5
- 134 217 728
- 262 144
- 2 048
- 128
- f800:0:0:0:0:0:0:0
- /4
- 268 435 456
- 524 288
- 4 096
- 256
- f000:0:0:0:0:0:0:0
- /3
- 536 870 912
- 1 048 576
- 8 192
- 512
- e000:0:0:0:0:0:0:0
- /2
- 1 073 741 824
- 2 097 152
- 16 384
- 1 024
- c000:0:0:0:0:0:0:0
- /1
- 2 147 483 648
- 4 194 304
- 32 768
- 2 048
- 8000:0:0:0:0:0:0:0
- /0
- 4 294 967 296
- 8 388 608
- 65 536
- 4 096
- 0:0:0:0:0:0:0:0

4.0 Current Distribution

4.1 Allocated Space

According to the IPv6 Global Unicast Address Assignments list from IANA (last updated in Nov 2024), there have been 34 allocations made to the five Regional Internet Registries in total so far. This is equivalent to about 8 445 440 IPv6 /32 subnets which is approximately 0.197% of the total available¹¹ IPv6 space.

- Designation / Allocations made
- Allocations / Percentage¹²
- Prefix(es)

- APNIC
  1999–2024
- 9 allocations
  ≅ 0.0493%
- 2001:200::/23 2001:c00::/23 2001:e00::/23 2001:4400::/23 2001:8000::/19 2001:a000::/20 2001:b000::/20 2400::/12 2410::/12
- ARIN
  1999–2019
- 7 allocations
  ≅ 0.0489%
- 2001:400::/23 2001:1800::/23 2001:4800::/23 2600::/12 2610::/23 2620::/23 2630::/12
- RIPE NCC
  1999–2019
- 14 allocations
  ≅ 0.0496%
- 2001:600::/23 2001:800::/22 2001:1400::/22 2001:1a00::/23 2001:1c00::/22 2001:2000::/19 2001:4000::/23 2001:4600::/23 2001:4a00::/23 2001:4c00::/23 2001:5000::/20 2003::/18 2a00::/12 2a10::/12
- LACNIC
  2002–2006
- 2 allocations
  ≅ 0.0244%
- 2001:1200::/23 2800::/12
- AFRINIC
  2004–2006
- 2 allocations
  ≅ 0.0244%
- 2001:4200::/23 2c00::/12