IPv6 subnetting reference

This IPv6 subnetting reference lists the sizes for IPv6 subnetworks. Different types of network links may require different subnet sizes.^[1] 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.^[2]

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[3] (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[4]
|8
4

See also

• IPv6 address
• Classless Inter-Domain Routing (CIDR)
• IPv4 subnetting reference

References

1. ↑ ARIN IPv6 Addressing Plans
2. ↑ RIPE IP Allocation Rates
3. ↑ RFC 6177 IPv6 Address Assignment to End Sites
4. ↑ IANA IPv6 unicast address assignments

External links

• RFC 5375 "IPv6 Unicast Address Assignment Considerations", December 2008
• Preparing an IPv6 Address Plan Manual of national research and education network SURFnet