Editing Classless Inter-Domain Routing (section)

===IPv6 CIDR blocks===
{| class="wikitable" style="text-align: center; margin-left: auto; margin-right: auto; border: none;"
|+ IPv6 CIDR prefixes
|-
! rowspan="2" | Prefix size !! colspan="3" | Number of equivalent subnets !! rowspan="2" | Interface ID bits
|-
! /48 !! /56 !! /64 
|-
| /24 || 16M || 4G || 1T || 104
|-
| /25 || 8M || 2G || 512G || 103
|-
| /26 || 4M || 1G || 256G || 102
|-
| /27 || 2M || 512M || 128G || 101
|-
| /28 || 1M || 256M || 64G || 100
|-
| /29 || 512K || 128M || 32G || 99
|-
| /30 || 256K || 64M || 16G || 98
|-
| /31 || 128K || 32M || 8G || 97
|-
| /32 || 64K || 16M || 4G || 96
|-
| /33 || 32K || 8M || 2G || 95
|-
| /34 || 16K || 4M || 1G || 94
|-
| /35 || 8K || 2M || 512M || 93
|-
| /36 || 4K || 1M || 256M || 92
|-
| /37 || 2K || 512K || 128M || 91
|-
| /38 || 1K || 256K || 64M || 90
|-
| /39 || 512 || 128K || 32M || 89
|-
| /40 || 256 || 64K || 16M || 88
|-
| /41 || 128 || 32K || 8M || 87
|-
| /42 || 64 || 16K || 4M || 86
|-
| /43 || 32 || 8K || 2M || 85
|-
| /44 || 16 || 4K || 1M || 84
|-
| /45 || 8 || 2K || 512K || 83
|-
| /46 || 4 || 1K || 256K || 82
|-
| /47 || 2 || 512 || 128K || 81
|-
| /48 || 1 || 256 || 64K || 80
|-
| /49 ||  || 128 || 32K || 79
|-
| /50 ||  || 64 || 16K || 78
|-
| /51 ||  || 32 || 8K || 77
|-
| /52 ||  || 16 || 4K || 76
|-
| /53 ||  || 8 || 2K || 75
|-
| /54 ||  || 4 || 1K || 74
|-
| /55 ||  || 2 || 512 || 73
|-
| /56 ||  || 1 || 256 || 72
|-
| /57 ||  ||  || 128 || 71
|-
| /58 ||  ||  || 64 || 70
|-
| /59 ||  ||  || 32 || 69
|-
| /60 ||  ||  || 16 || 68
|-
| /61 ||  ||  || 8 || 67
|-
| /62 ||  ||  || 4 || 66
|-
| /63 ||  ||  || 2 || 65
|-
| /64 ||  ||  || 1 || 64
|-
| colspan="5" | '''K''' = 1,024 
|-
| colspan="5" | '''M''' = 1,048,576
|-
| colspan="5" | '''G''' = 1,073,741,824
|-
| colspan="5" | '''T''' = 1,099,511,627,776
|}
The large address size of IPv6 permitted worldwide route summarization and guaranteed sufficient address pools at each site. The standard subnet size for IPv6 networks is a {{IPaddr||64}} block, which is required for the operation of [[IPv6 stateless address autoconfiguration|stateless address autoconfiguration]].<ref name="RFC 4862">{{IETF RFC|4862}}</ref> At first, the IETF recommended in {{IETF RFC|3177}} as a best practice that all end sites receive a {{IPaddr||48}} address allocation,<ref name="RFC 3177">{{cite IETF |rfc=3177 |title=IAB/IESG Recommendation on IPv6 Address Allocations to Sites |publisher=IAB/IESG |date=September 2001}}</ref> but criticism and reevaluation of actual needs and practices has led to more flexible allocation recommendations in {{IETF RFC|6177}}<ref name="RFC 6177">{{cite IETF |rfc=6177 |title=IPv6 Address Assignment to End Sites |author=T. Narten |author2=G. Huston |author3=L. Roberts |date=March 2011}}</ref> suggesting a significantly smaller allocation for some sites, such as a {{IPaddr||56}} block for residential networks.

This '''IPv6 subnetting reference''' lists the sizes for IPv6 [[subnetwork]]s. Different types of network links may require different subnet sizes.<ref>{{cite web|url=http://www.getipv6.info/index.php/IPv6_Addressing_Plans |title=ARIN IPv6 Addressing Plans |publisher=Getipv6.info |date=2016-03-25 |access-date=2018-03-12}}</ref> 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 each network.<ref>{{cite web |url=https://www.ripe.net/info/info-services/addressing.html |title=RIPE IP Allocation Rates |archive-url=https://web.archive.org/web/20110203130851/http://ripe.net/info/info-services/addressing.html |archive-date=2011-02-03}}</ref>

 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 [[IPv6#Stateless_address_autoconfiguration_(SLAAC)|SLAAC]]
 |||| |||| |||| ||60   Some (very limited) [[6rd]] deployments (/60 = 16 /64 blocks)
 |||| |||| |||| |56   Minimal end sites assignment;<ref name="RFC 6177"/> e.g. [[home network]] (/56 = 256 /64 blocks)
 |||| |||| |||| 52   /52 block = 4096 /64 blocks
 |||| |||| |||48   Typical assignment for larger sites (/48 = 65536 /64 blocks)
 |||| |||| ||44
 |||| |||| |40
 |||| |||| 36   possible future [[local Internet registry]] (LIR) extra-small allocations
 |||| |||32   LIR minimum allocations
 |||| ||28   LIR medium allocations
 |||| |24   LIR large allocations
 |||| 20   LIR extra large allocations
 |||16
 ||12   [[Regional Internet registry]] (RIR) allocations from IANA<ref>{{cite web|url=https://www.iana.org/assignments/ipv6-unicast-address-assignments/ipv6-unicast-address-assignments.xml |title=IANA IPv6 unicast address assignments |publisher=Iana.org |access-date=2018-03-12}}</ref>
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