A Regional Internet registry (RIR) is a nonprofit organization that manages the allocation and registration of Internet number resources, namely IPv4 addresses, IPv6 addresses and Autonomous System Numbers (ASNs), within a defined region of the world. In Internet governance, RIRs form the middle tier of the number resource hierarchy: they receive large blocks from the Internet Assigned Numbers Authority (IANA) and distribute them to Internet service providers, hosting companies, enterprises and other network operators in their service region.
There are five RIRs, and together they cover the entire globe. Each is a membership organization whose allocation rules are written through an open, bottom-up policy process in which anyone may participate, which makes the RIR system one of the clearest working examples of multistakeholder governance.
The five regional Internet registries
The RIR system grew from the 1990s onward, when centralized registration could no longer keep pace with the growth of the Internet. Each registry was created by its own regional community and later recognized globally. The table below lists the five registries and their service regions.
| RIR | Service region | Established | Headquarters |
|---|---|---|---|
| RIPE NCC | Europe, the Middle East and parts of Central Asia | 1992 | Amsterdam |
| APNIC | Asia-Pacific | 1993 | Brisbane |
| ARIN | Canada, the United States and parts of the Caribbean | 1997 | Chantilly, Virginia |
| LACNIC | Latin America and parts of the Caribbean | 2002 | Montevideo |
| AFRINIC | Africa and the Indian Ocean region | 2005 | Ebene, Mauritius |
The five registries coordinate through the Number Resource Organization (NRO), which also acts as the Address Supporting Organization within the ICANN structure. Through this channel they agree on global policies, such as the rules under which IANA hands blocks to RIRs, while keeping regional policies under regional control.
How the number allocation hierarchy works
Internet number resources flow through a delegation chain of three or four levels. Each level receives a block from the level above, justifies its need, and passes smaller blocks downward, which keeps every address unique worldwide and traceable to a registered holder.
| Level | Role | Typical block it handles |
|---|---|---|
| IANA | Holds the global pools and delegates to RIRs | IPv4 /8 historically, IPv6 /12 |
| RIR | Allocates to members in its region | IPv6 /32 to /29, ASNs, small IPv4 blocks |
| National Internet registry | Exists in some Asian and Latin American countries | Sub-allocations within one country |
| Local Internet registry | Usually an ISP that assigns to customers | IPv6 /48 or /56 per site, single IPv4 addresses |
Allocation is based on demonstrated need, not on purchase. A member requesting space must show how it will be used, and the RIR records the holder in its public registry database. For IPv6, where space is plentiful, the default allocation to a new ISP is commonly a /32 or /29, which allows it to give each customer site a /48 or /56.
Core services an RIR provides
Allocating numbers is only part of the work. An RIR maintains the authoritative record of who holds which resource, and many critical operational systems rely on that record being accurate.
- Registration services: allocation and assignment of IPv4, IPv6 and ASNs, and registration of transfers.
- Registry database: public lookups through WHOIS and RDAP, including abuse contact details for each network.
- Reverse DNS delegation: delegating in-addr.arpa and ip6.arpa zones so that addresses can resolve to names.
- RPKI certification: issuing resource certificates so holders can sign Route Origin Authorizations that protect against BGP hijacks.
- Policy development and community events: open mailing lists and regular meetings where rules are proposed and debated.
- Training and measurement: technical courses and network measurement platforms for the region.
Of these, RPKI has become a central security function. Network operators validate BGP announcements against RIR-signed data and reject routes whose origin does not match, so the RIR registry now directly affects which routes the Internet accepts.
Policy development and governance
RIR rules are made by open, consensus-based policy development processes. Anyone, member or not, can submit a proposal; it is discussed on public mailing lists and at regional meetings, and community chairs judge whether rough consensus has been reached. The RIR’s staff then implement the adopted policy.
Each RIR is also a membership organization with an elected board. Members pay annual fees, usually scaled by the amount of address space they hold, and the fees fund the registry’s operation rather than the purchase of addresses. This dual structure separates policy, which belongs to the community, from corporate governance, which belongs to members. The model has been tested by disputes, most visibly in AFRINIC, where litigation and governance crises in the early 2020s disrupted normal operation and prompted debate about how the RIR system should handle a registry in distress.
IPv4 exhaustion and its effect on RIRs
The RIR role changed sharply when the IPv4 free pool ran out. IANA distributed its last /8 blocks to the five RIRs in February 2011, and each RIR then reached its own final stage of distribution over the following decade. After exhaustion, RIRs shifted from distributing IPv4 space to registering transfers and maintaining waiting lists.
| Aspect | Before exhaustion | After exhaustion |
|---|---|---|
| IPv4 allocation | Needs-based blocks from a free pool | Small final blocks or waiting lists only |
| IPv4 transfers | Rare and tightly restricted | Common, registered market transfers |
| IPv6 allocation | Available but little demand | Actively promoted and easy to obtain |
| Registry accuracy | Important for routing and abuse handling | Also critical for proving ownership in sales |
A common misconception is that RIRs sell IPv4 addresses. They do not; buyers and sellers agree on prices privately, and the RIR only checks policy compliance and updates the registry. Another is that RIRs control routing; they record holdership, but each network still decides which announcements to accept.
A plain-language summary
Every device on the Internet needs a unique number, much as every house needs a unique postal address. A regional Internet registry is the office that hands out these numbers for one part of the world and keeps the official list of who has which ones.
There are five such offices, one for each large region. Internet providers get their numbers from them and then pass smaller sets to their customers. This system keeps every address unique and makes it possible to find out who is responsible for any network when something goes wrong.
An example from practice
A regional fiber provider in Central Europe has grown from a few hundred to 40,000 subscribers and wants to stop depending on its upstream provider’s address space. It becomes a member of the RIPE NCC, which makes it a local Internet registry.
The provider receives a /29 IPv6 allocation and an Autonomous System Number, publishes its routing policy in the registry, and creates RPKI Route Origin Authorizations for its prefixes. Because no new IPv4 space is available, it buys a /22 from another holder and has the transfer registered by the RIR. The provider then announces its own prefixes over BGP to two transit providers, giving it multihoming and a clear abuse contact in the public database.