Editing Private network (section)

==Private IPv6 addresses==
{{Main article|Unique local address}}
The concept of private networks has been extended in the next generation of the [[Internet Protocol]], [[IPv6]], and special address blocks are reserved.

The address block {{IPaddr|fc00::|7}} is reserved by IANA for unique local addresses (ULAs).<ref name=rfc4193 /> They are [[unicast]] addresses, but contain a 40-bit random number in the routing prefix to prevent collisions when two private networks are interconnected. Despite being inherently ''local'' in usage, the [[IPv6 address#Address scopes|IPv6 address scope]] of unique local addresses is global.

The first block defined is {{IPaddr|fd00::|8}}, designed for {{IPaddr||48}} routing blocks, in which users can create multiple subnets, as needed.

{| class="wikitable"
! RFC 4193 Block !! Prefix/L !! Global ID (random) !! Subnet ID !! Number of addresses in subnet
|-
|  
| colspan="2" | 48 bits
| 16 bits || 64 bits
|-
| fd00::/8 || fd || xx:xxxx:xxxx || yyyy || {{gaps|18|446|744|073|709|551|616}}
|}

Examples:
{| class="wikitable"
! Prefix/L !! Global ID (random) !! Subnet ID !! Interface ID !! Address !! Subnet
|-
| fd || xx:xxxx:xxxx || yyyy || zzzz:zzzz:zzzz:zzzz
| fdxx:xxxx:xxxx:yyyy:zzzz:zzzz:zzzz:zzzz
| fdxx:xxxx:xxxx:yyyy::/64
|-
| fd || 12:3456:789a || 0001 || 0000:0000:0000:0001
| fd12:3456:789a:1::1
| fd12:3456:789a:1::/64
|}

A former standard proposed the use of ''site-local'' addresses in the {{IPaddr|fec0::|10}} block, but because of scalability concerns and poor definition of what constitutes a ''site'', its use has been deprecated since September 2004.{{Ref RFC|3879}}