This IPv6 subnetting reference lists the sizes for IPv6 subnetworks. Different types of network links may require different subnet sizes. The subnet mask separates the bits of the network identifier prefix from the bits of the interface identifier. Selecting a smaller prefix size results in fewer number of networks covered, but with more addresses within those networks.
Stateless address autoconfiguration works only with /64 prefixes.
CIDR Prefixes
2001:0db8:0123:4567:89ab:cdef:1234:5678 |||| |||| |||| |||| |||| |||| |||| |||| |||| |||| |||| |||| |||| |||| |||| |||128 Single end-points and loopback |||| |||| |||| |||| |||| |||| |||| |||127 Point-to-point links (inter-router) |||| |||| |||| |||| |||| |||| |||| ||124 |||| |||| |||| |||| |||| |||| |||| |120 |||| |||| |||| |||| |||| |||| |||| 116 |||| |||| |||| |||| |||| |||| |||112 |||| |||| |||| |||| |||| |||| ||108 |||| |||| |||| |||| |||| |||| |104 |||| |||| |||| |||| |||| |||| 100 |||| |||| |||| |||| |||| |||96 |||| |||| |||| |||| |||| ||92 |||| |||| |||| |||| |||| |88 |||| |||| |||| |||| |||| 84 |||| |||| |||| |||| |||80 |||| |||| |||| |||| ||76 |||| |||| |||| |||| |72 |||| |||| |||| |||| 68 |||| |||| |||| |||64 Single LAN (default prefix size for SLAAC) |||| |||| |||| ||60 Some (very limited) 6rd deployments (/60 = 16 /64) |||| |||| |||| |56 Minimal end sites assignment (e.g. Home network) (/56 = 256 /64) |||| |||| |||| 52 (/52 = 4096 /64) |||| |||| |||48 Typical assignment for larger sites (/48 = 65536 /64) - Many ISP also do for residential |||| |||| ||44 |||| |||| |40 |||| |||| 36 possible future Local Internet registry extra-small allocations |||| |||32 Local Internet registry minimum allocations |||| ||28 Local Internet registry medium allocations |||| |24 Local Internet registry large allocations |||| 20 Local Internet registry extra large allocations |||16 ||12 Regional Internet Registry allocations from IANA |8 4References
IPv6 subnetting reference Wikipedia(Text) CC BY-SA