The Regional Internet Registry (RIR) Allocation Hierarchy Explained
An architectural breakdown of the global Internet Numbers Registry System, exploring how IP addresses and Autonomous System Numbers cascade from IANA down to regional and local networks.
Quick Answer
The Internet Numbers Registry System (RFC 7020) governs IP address distribution through a strict five-tier hierarchical model: IANA delegates large prefix blocks to five Regional Internet Registries (RIRs); RIRs allocate blocks to National Registries (NIRs) or Local Registries (LIRs/ISPs); and LIRs assign operational subnets to end-user organizations.
- Five Sovereign RIRs: ARIN, RIPE NCC, APNIC, LACNIC, and AFRINIC manage global geographic zones.
- Allocation vs Assignment: Allocations allow sub-delegation to downstream customers; assignments do not.
- Inter-RIR Transfer Markets: Reallocated IPv4 blocks move between regions under reciprocal transfer agreements.
1. The Five Tiers of Number Delegation
Global Internet routing scalability relies on unambiguous, non-overlapping ownership of IP prefixes and Autonomous System Numbers:
2. Comparison of the Five Regional Registries
Compare the operational jurisdictions, policy bodies, and headquarters across all five RIRs:
| RIR Name | Headquarters Location | Regional Jurisdiction | IPv4 Run-out Date | Primary Database Format |
|---|---|---|---|---|
| ARIN | Chantilly, Virginia, USA | United States, Canada, select Caribbean islands | September 2015 | REST / XML / RDAP |
| RIPE NCC | Amsterdam, Netherlands | Europe, Middle East, Central Asia | September 2012 (Final /8) | RPSL / RDAP |
| APNIC | Brisbane, Australia | Asia and Pacific region (56 economies) | April 2011 (Final /8) | RPSL / RDAP |
| LACNIC | Montevideo, Uruguay | Latin America and Caribbean (33 territories) | June 2014 | RPSL / RDAP |
| AFRINIC | Ebène, Mauritius | African continent and Indian Ocean islands | January 2020 (Phase 2) | RPSL / RDAP |
RIR Number Delegation Hierarchy Decision Tree
[ ICANN / IANA Global Root ]
|
+----------------------+----------------------+
| | |
[ ARIN ] [ RIPE NCC ] [ APNIC ]
North America Europe & Mid-East Asia-Pacific
| | |
[ LIR / ISP ] [ LIR / ISP ] [ NIR (CNNIC, JPNIC) ]
Major Telecom Core National Providers |
| | [ LIR / ISP ]
+----------------------+----------------------+
|
[ End-User Assignment ]
Enterprise Office / Data Center
/24 to /29 static subnet
3. Allocation vs Assignment: Legal and Routing Distinctions
A frequent source of confusion in WHOIS records is the distinction between an Allocation and an Assignment:
- Allocation: A large block granted to an ISP or LIR. The recipient is legally authorized to carve the block into smaller sub-allocations for downstream customers or assign subnets to internal network segments.
- Assignment: An operational block provided to an end-user organization (such as a university or hospital) purely to address their own servers and workstations. The recipient cannot sub-lease, partition, or reassign these IPs to third parties.
4. Practical Diagnostics: Querying IANA Master Registry via API
Inspect the authoritative IANA RDAP bootstrap registry directly from the terminal:
Frequently Asked Questions
What is the precise difference between an IP "Allocation" and an IP "Assignment"?
An Allocation is a block of IP space delegated to an LIR or ISP for further sub-delegation to customers and downstream networks. An Assignment is an IP block designated exclusively for operational use on a specific network infrastructure, with no rights to further sub-allocate or resell to third parties.
What is a National Internet Registry (NIR)?
An NIR operates under an RIR to manage number resources at a country level. Under APNIC, countries like China (CNNIC), Japan (JPNIC), South Korea (KRNIC), and Taiwan (TWNIC) maintain their own NIR databases where domestic ISPs register subnets before syncing with APNIC.
When did IANA officially exhaust its free pool of unallocated IPv4 addresses?
IANA depleted its central pool of unallocated IPv4 /8 blocks on February 3, 2011, when it distributed the final five reserve blocks equally among the five RIRs. Subsequently, each RIR reached their own exhaustion thresholds (APNIC in 2011, RIPE NCC in 2012, LACNIC in 2014, ARIN in 2015, and AFRINIC in 2020), prompting the creation of formal IPv4 transfer markets.
Can an organization transfer IP addresses between different RIR regions (e.g. ARIN to RIPE)?
Yes, via an Inter-RIR Transfer. Both the source and destination RIR must support reciprocal transfer policies (e.g., ARIN Policy 8.4 and RIPE NCC Transfer Policy). The buyer must demonstrate technical justification (need) for the addresses under the destination RIR rules.
Data & Technical Sources
- IETF RFC 7020 — The Internet Numbers Registry System
- IETF RFC 2050 — Internet Registry IP Allocation Guidelines
- IANA IPv4 Address Space Registry — Master global delegation table of all 256 /8 prefixes