A special-use domain name is a domain name that is defined and reserved in the hierarchy of the Domain Name System of the Internet for special purposes. The designation of a reserved special-use domain is authorized by the Internet Engineering Task Force (IETF) and executed, maintained, and published by the Internet Assigned Numbers Authority (IANA). [1]
The following list comprises the domain names list by IANA in the category of special-use domain names. [2]
| Domain | Purpose | Authority document |
|---|---|---|
| alt. | preventing name collisions with DNS | RFC 9476 |
| 6tisch.arpa. | IETF 6TiSH working group | RFC 9031 |
| 10.in-addr.arpa. | private network reverse mapping | RFC 6761 |
| 16.172.in-addr.arpa. | ||
| 17.172.in-addr.arpa. | ||
| 18.172.in-addr.arpa. | ||
| 19.172.in-addr.arpa. | ||
| 20.172.in-addr.arpa. | ||
| 21.172.in-addr.arpa. | ||
| 22.172.in-addr.arpa. | ||
| 23.172.in-addr.arpa. | ||
| 24.172.in-addr.arpa. | ||
| 25.172.in-addr.arpa. | ||
| 26.172.in-addr.arpa. | ||
| 27.172.in-addr.arpa. | ||
| 28.172.in-addr.arpa. | ||
| 29.172.in-addr.arpa. | ||
| 30.172.in-addr.arpa. | ||
| 31.172.in-addr.arpa. | ||
| 168.192.in-addr.arpa. | ||
| 170.0.0.192.in-addr.arpa. | NAT64 prefix discovery (RFC 7050) | RFC 8880 |
| 171.0.0.192.in-addr.arpa. | ||
| ipv4only.arpa. | ||
| 254.169.in-addr.arpa. | Use in multicast DNS (mDNS) | RFC 6762 |
| 8.e.f.ip6.arpa. | ||
| 9.e.f.ip6.arpa. | ||
| a.e.f.ip6.arpa. | ||
| b.e.f.ip6.arpa. | ||
| home.arpa. | Non-unique use on residential networks | RFC 8375 |
| example. | documentation, tutorials, etc. | RFC 6761 |
| example.com. | use in documentation, tutorials, testing | RFC 6761 |
| example.net. | ||
| example.org. | ||
| invalid. | Avoidance of confusion and errors per RFC 2606 | RFC 6761 |
| local. | Used for Multicast DNS | RFC 6762 (Section 3) |
| localhost. | Reserved to avoidance of confusion and errors | RFC 6761 |
| onion. | Anonymous onion service | RFC 7686 |
| test. | Avoidance of confusion, allowing use for documentation and network testing | RFC 6761 |
Internet Protocol version 4 (IPv4) is the fourth version of the Internet Protocol (IP). It is one of the core protocols of standards-based internetworking methods in the Internet and other packet-switched networks. IPv4 was the first version deployed for production on SATNET in 1982 and on the ARPANET in January 1983. It is still used to route most Internet traffic today, even with the ongoing deployment of Internet Protocol version 6 (IPv6), its successor.
A top-level domain (TLD) is one of the domains at the highest level in the hierarchical Domain Name System of the Internet after the root domain. The top-level domain names are installed in the root zone of the name space. For all domains in lower levels, it is the last part of the domain name, that is, the last non empty label of a fully qualified domain name. For example, in the domain name www.example.com, the top-level domain is .com. Responsibility for management of most top-level domains is delegated to specific organizations by the ICANN, an Internet multi-stakeholder community, which operates the Internet Assigned Numbers Authority (IANA), and is in charge of maintaining the DNS root zone.
A multicast address is a logical identifier for a group of hosts in a computer network that are available to process datagrams or frames intended to be multicast for a designated network service. Multicast addressing can be used in the link layer, such as Ethernet multicast, and at the internet layer for Internet Protocol Version 4 (IPv4) or Version 6 (IPv6) multicast.
The Internet Assigned Numbers Authority (IANA) is a standards organization that oversees global IP address allocation, autonomous system number allocation, root zone management in the Domain Name System (DNS), media types, and other Internet Protocol–related symbols and Internet numbers.
ISO 3166-1 alpha-2 codes are two-letter country codes defined in ISO 3166-1, part of the ISO 3166 standard published by the International Organization for Standardization (ISO), to represent countries, dependent territories, and special areas of geographical interest. They are the most widely used of the country codes published by ISO, and are used most prominently for the Internet's country code top-level domains. They are also used as country identifiers extending the postal code when appropriate within the international postal system for paper mail, and have replaced the previous one consisting one-letter codes. They were first included as part of the ISO 3166 standard in its first edition in 1974.
An autonomous system (AS) is a collection of connected Internet Protocol (IP) routing prefixes under the control of one or more network operators on behalf of a single administrative entity or domain, that presents a common and clearly defined routing policy to the Internet. Each AS is assigned an autonomous system number (ASN), for use in Border Gateway Protocol (BGP) routing. Autonomous System Numbers are assigned to Local Internet Registries (LIRs) and end user organizations by their respective Regional Internet Registries (RIRs), which in turn receive blocks of ASNs for reassignment from the Internet Assigned Numbers Authority (IANA). The IANA also maintains a registry of ASNs which are reserved for private use.
In Internet networking, a private network is a computer network that uses a private address space of IP addresses. These addresses are commonly used for local area networks (LANs) in residential, office, and enterprise environments. Both the IPv4 and the IPv6 specifications define private IP address ranges.
The domain name arpa is a top-level domain (TLD) in the Domain Name System (DNS) of the Internet. It is used predominantly for the management of technical network infrastructure. Prominent among such functions are the subdomains in-addr.arpa and ip6.arpa, which provide namespaces for reverse DNS lookup of IPv4 and IPv6 addresses, respectively.
The domain names example.com, example.net, example.org, and example.edu are second-level domain names in the Domain Name System of the Internet. They are reserved by the Internet Assigned Numbers Authority (IANA) at the direction of the Internet Engineering Task Force (IETF) as special-use domain names for documentation purposes. The domain names are used widely in books, tutorials, sample network configurations, and generally as examples for the use of domain names. The Internet Corporation for Assigned Names and Numbers (ICANN) operates web sites for these domains with content that reflects their purpose.
Single-letter second-level domains are domains in which the second-level domain of the domain name consists of only one letter, such as x.com. In 1993, the Internet Assigned Numbers Authority (IANA) explicitly reserved all single-letter and single-digit second-level domains under the top-level domains com, net, and org, and grandfathered those that had already been assigned. In December 2005, ICANN considered auctioning these domain names.
.test is a reserved top-level domain intended for usage in software testing. It is guaranteed to never be registered into the Internet.
In the Internet addressing architecture, the Internet Engineering Task Force (IETF) and the Internet Assigned Numbers Authority (IANA) have reserved various Internet Protocol (IP) addresses for special purposes.
In computer networking, a port or port number is a number assigned to uniquely identify a connection endpoint and to direct data to a specific service. At the software level, within an operating system, a port is a logical construct that identifies a specific process or a type of network service. A port at the software level is identified for each transport protocol and address combination by the port number assigned to it. The most common transport protocols that use port numbers are the Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP); those port numbers are 16-bit unsigned numbers.
A unique local address (ULA) is an Internet Protocol version 6 (IPv6) address in the address range fc00::/7. These addresses are non-globally reachable. For this reason, ULAs are somewhat analogous to IPv4 private network addressing, but with significant differences. Unique local addresses may be used freely, without centralized registration, inside a single site or organization or spanning a limited number of sites or organizations.
Blackhole DNS servers are Domain Name System (DNS) servers that return a "nonexistent address" answer to reverse DNS lookups for addresses reserved for private use.
An Internet Protocol Version 6 address is a numeric label that is used to identify and locate a network interface of a computer or a network node participating in a computer network using IPv6. IP addresses are included in the packet header to indicate the source and the destination of each packet. The IP address of the destination is used to make decisions about routing IP packets to other networks.
A Uniform Resource Locator (URL), colloquially known as an address on the Web, is a reference to a resource that specifies its location on a computer network and a mechanism for retrieving it. A URL is a specific type of Uniform Resource Identifier (URI), although many people use the two terms interchangeably. URLs occur most commonly to reference web pages (HTTP/HTTPS) but are also used for file transfer (FTP), email (mailto), database access (JDBC), and many other applications.
mcast.net is a second level domain reserved by the Internet Assigned Numbers Authority (IANA) and maintained by Verisign used to bind DNS records unique to multicast addressing. The domain and its subdomains are not associated with any web site.
