Nibble boundary
A boundary aligned on a four-bit hexadecimal digit. IPv6 reverse DNS is simplest when prefixes are delegated on nibble boundaries because each label in ip6.arpa represents one hexadecimal digit.
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Browse the glossaryIPv6 glossary — page 2
46 definitions associated with IPv6.
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Page 2 of 2NUD
Neighbor Unreachability Detection, the Neighbor Discovery process that tracks whether a neighbor is reachable and probes when necessary. Neighbor-cache entries move through states such as REACHABLE, STALE, DELAY, and PROBE.
Read definitionO flag
The Other Configuration flag in a Router Advertisement, indicating that hosts should use DHCPv6 for information other than addresses, such as DNS or domain search data. Host behavior is implementation-dependent.
Read definitionPref64
An IPv6 prefix used by NAT64 to embed or represent IPv4 destinations. Networks can advertise a Pref64 in Router Advertisements, and DNS64 uses a configured prefix for synthesis.
Read definitionPreferred lifetime
The period during which an IPv6 address or prefix is preferred for new communication. After it expires but before valid lifetime ends, the resource is deprecated and should generally not be selected for new sessions.
Read definitionPrefix Information Option (PIO)
A Router Advertisement option describing an IPv6 prefix, its valid and preferred lifetimes, and whether it is on-link or autonomous for SLAAC.
Read definitionPrefix policy
Host rules that rank source and destination address pairs, influencing address selection when multiple IPv4 and IPv6 choices exist. Policy can affect which DNS answer a client actually uses.
Read definitionRA
Router Advertisement, an ICMPv6 message that communicates default-router and prefix information and can provide DNS, MTU, route, and Pref64 options.
Read definitionRDNSS
Recursive DNS Server option in IPv6 Router Advertisements. It allows routers to advertise recursive resolver addresses without DHCPv6.
Read definitionRouter Advertisement
The full name for RA, an ICMPv6 message that announces routers, prefixes, lifetimes, flags, MTU, DNS information, routes, and other link configuration.
Read definitionRouter Solicitation
An ICMPv6 message sent by a host to prompt routers to send Router Advertisements sooner than the normal unsolicited interval. It is commonly abbreviated RS.
Read definitionRS
Router Solicitation, an ICMPv6 message that asks local routers to send Router Advertisements.
Read definitionSAVI
Source Address Validation Improvement, a family of mechanisms that binds IP source addresses to attachment points to reduce spoofing. SAVI can use DHCP, Neighbor Discovery, or other control-plane evidence.
Read definitionSite-local address
A deprecated IPv6 unicast scope formerly associated with fec0::/10. It was replaced operationally by Unique Local Addresses and should not be used in new designs.
Read definitionSLAAC
Stateless Address Autoconfiguration, by which an IPv6 host forms addresses from Router Advertisement prefixes without a DHCPv6 address lease. DHCPv6 can still provide other configuration, and address registration can improve visibility.
Read definitionSource address selection
Host logic for choosing the most appropriate source address for a destination based on scope, deprecation, label, precedence, and prefix matching. Incorrect choices can cause asymmetric or failed connectivity.
Read definitionSSAC
A mistaken or informal rendering sometimes used for SLAAC. The standardized acronym is SLAAC, Stateless Address Autoconfiguration.
Read definitionTentative address
An IPv6 address assigned to an interface but not yet usable for normal communication while Duplicate Address Detection is in progress.
Read definitionULA
Unique Local Address, an IPv6 unicast address from fc00::/7 intended for local communications and not expected to be globally routed. Locally assigned ULAs normally use fd00::/8 with a pseudo-random global ID.
Read definitionUnique Local Address
The expanded name of ULA. It provides organization-local IPv6 addressing without relying on provider-assigned global prefixes, though collision avoidance remains important during network mergers.
Read definitionValid lifetime
The period during which an IPv6 address or delegated prefix remains valid for existing and new use, subject to preferred-state rules. When it expires, the resource must not be used.
Read definitionZone ID
An interface or scope identifier appended to a scoped IPv6 address in local APIs, such as fe80::1%eth0. It disambiguates which link is intended for a non-global address.
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