U-label
A Unicode form of an internationalized DNS label intended for user display and processing under IDNA rules. Its corresponding DNS-compatible A-label uses Punycode.
Read definitionAlphabetical glossary
U glossary terms
11 definitions beginning with U.
11 terms
ULA
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 definitionUnicast
Delivery from one source to one destination address. Most ordinary host addresses are unicast, while anycast deliberately assigns the same unicast address to multiple nodes.
Read definitionUnified DDI
A management model in which DNS, DHCP, and IPAM share data, policy, workflows, and operational visibility rather than being administered as disconnected systems.
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 definitionUnmanaged address
An address observed on the network but not represented as an approved assignment in IPAM. It may be legitimate shadow IT, stale discovery, a security issue, or a documentation gap.
Read definitionUnsigned delegation
A delegation to a child zone without a parent DS record. From a signed parent it creates an intentional insecure boundary rather than a secure chain.
Read definitionUpdate prerequisite
A condition in a DNS UPDATE message that must be true before changes are applied, such as a name or RRset existing or not existing. Prerequisites support atomic conflict-aware updates.
Read definitionURL boot
Network boot in which firmware retrieves a boot image or configuration from an HTTP or HTTPS URL. DHCP or Router Advertisement options may supply the URI.
Read definitionuRPF
Unicast Reverse Path Forwarding, a source-validation technique that checks whether the routing table has an acceptable return path for a packet's source. Strict, loose, and feasible-path modes have different multihoming tradeoffs.
Read definitionUser class
Client-provided classification data used to select DHCP policy. DHCPv4 uses option 77, while DHCPv6 has OPTION_USER_CLASS.
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