IPv6 subnet matrix table

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This is a table of the IP block space available in various IPv6 prefixes.

The IPv6 Subnet Matrix Table[edit]

2001:0DB8:0400:000e:0000:0000:0000:402b
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

Examples[edit]

If you are granted a /64 prefix like 2001:0DB8:0400:000e::/64 then what's left after /64 in the table above is XXXX:XXXX:XXXX:XXXX. You have XXXX:XXXX:XXXX:XXXX (0000:0000:0000:0000 - FFFF:FFFF:FFFF:FFFF) at your disposal.

If you are handed a /124 prefix like 2001:0DB8:0400:000e:0000:0000:0000:402/124 then you are only left with X (0-F). Two are typically used to create the link, which leaves 14 IP's available to be used at your discretion.

The actual number of IPv6 in various subnet sizes[edit]

Prefix Number of IPv6 IPs Space
127 2 none
124 16 x
120 256 xx
64 18,446,744,073,709,551,616 xxxx:xxxx:xxxx:xxxx
48 1,208,925,819,614,629,174,706,176 xxxx:xxxx:xxxx:xxxx:xxxx
32 79,228,162,514,264,337,593,543,950,336 xxxx:xxxx:xxxx:xxxx:xxxx:xxxx

Requirements[edit]

You typically want/need a /64 for your home network. This is because /64 is the required size to use for autoconfiguraiton using radvd etc.. Smaller than /64 prefixes simply don't work with IPv6 autoconfiguration.

A /112 prefix (XXXX) or /96 (XXXX:XXXX) are nice sizes to allocate to each server in serverfarms etc.