Editing IPv6 (section)

===Stateless address autoconfiguration (SLAAC)===
{{See also|IPv6 address#Stateless address autoconfiguration (SLAAC)|l1=IPv6 address § Stateless address autoconfiguration}}

IPv6 hosts configure themselves automatically. Every interface has a self-generated link-local address and, when connected to a network, conflict resolution is performed and routers provide network prefixes via router advertisements.{{Ref RFC|4862}} Stateless configuration of routers can be achieved with a special router renumbering protocol.{{Ref RFC|2894}} When necessary, hosts may configure additional stateful addresses via [[DHCPv6|Dynamic Host Configuration Protocol version 6]] (DHCPv6) or static addresses manually.

Like IPv4, IPv6 supports globally unique [[IP address]]es. The design of IPv6 intended to re-emphasize the end-to-end principle of network design that was originally conceived during the establishment of the early Internet by rendering [[network address translation]] obsolete. Therefore, every device on the network is globally addressable directly from any other device.

A stable, unique, globally addressable IP address would facilitate tracking a device across networks. Therefore, such addresses are a particular privacy concern for mobile devices, such as laptops and cell phones.<ref>{{cite web|url=https://www.internetsociety.org/resources/deploy360/2014/privacy-extensions-for-ipv6-slaac/|title=Privacy Extensions for Stateless Address Autoconfiguration in IPv6|author=T. Narten|author2=R. Draves|author3=S. Krishnan|date=September 2007|website=www.ietf.org|access-date=13 March 2017}}</ref> To address these privacy concerns, the SLAAC protocol includes what are typically called "privacy addresses" or, more correctly, "temporary addresses".{{Ref RFC|8981}} Temporary addresses are random and unstable. A typical consumer device generates a new temporary address daily and will ignore traffic addressed to an old address after one week. Temporary addresses are used by default by Windows since XP SP1,<ref>{{Cite web |title=Overview of the Advanced Networking Pack for Windows XP |url=http://support.microsoft.com/kb/817778 |url-status=dead |archive-url=https://web.archive.org/web/20170907013704/https://support.microsoft.com/en-us/help/817778/overview-of-the-advanced-networking-pack-for-windows-xp |archive-date=7 September 2017 |access-date=15 April 2019 |publisher=[[Microsoft]] }}</ref> macOS since (Mac&nbsp;OS&nbsp;X) 10.7, Android since 4.0, and iOS since version 4.3. Use of temporary addresses by Linux distributions varies.<ref>{{Cite web |date=8 August 2014 |title=Privacy Extensions for IPv6 SLAAC |url=https://www.internetsociety.org/resources/deploy360/2014/privacy-extensions-for-ipv6-slaac |url-status=live |archive-url=https://web.archive.org/web/20231023063407/https://www.internetsociety.org/resources/deploy360/2014/privacy-extensions-for-ipv6-slaac/ |archive-date=23 October 2023 |access-date=17 January 2020 |publisher=[[Internet Society]] }}</ref>

Renumbering an existing network for a new connectivity provider with different routing prefixes is a major effort with IPv4.<ref>{{Cite web |last1=Ferguson |first1=P. |last2=Berkowitz |first2=H. |date=January 1997 |title=Network Renumbering Overview: Why would I want it and what is it anyway? |url=https://datatracker.ietf.org/doc/html/rfc2071 |url-status=live |archive-url=https://web.archive.org/web/20240107145323/https://datatracker.ietf.org/doc/html/rfc2071 |archive-date=7 January 2024 |publisher=[[IETF]] |doi=10.17487/RFC2071 |rfc=2071 }}</ref><ref>{{Cite web |last=Berkowitz |first=H. |date=January 1997 |title=Router Renumbering Guide |url=https://datatracker.ietf.org/doc/html/rfc2072 |url-status=live |archive-url=https://web.archive.org/web/20230608094931/https://datatracker.ietf.org/doc/html/rfc2072 |archive-date=8 June 2023 |publisher=[[IETF]] |doi=10.17487/RFC2072 |rfc=2072 }}</ref> With IPv6, however, changing the prefix announced by a few routers can in principle renumber an entire network, since the host identifiers (the least-significant 64 bits of an address) can be independently self-configured by a host.{{Ref RFC|4862}}

The SLAAC address generation method is implementation-dependent. IETF recommends that addresses be deterministic but semantically opaque.<ref>{{Cite IETF|rfc=8064|title=Recommendation on Stable IPv6 Interface Identifiers|first1=Alissa|last1=Cooper|first2=Fernando|last2=Gont|first3=Dave|last3=Thaler}}</ref>