Handing Out IP Addresses
IANA manages the global pool of IP addresses, but a single organization cannot efficiently hand out individual IP address blocks to every ISP, university, and cloud provider in the world. The scale is too large and the regional context too important.
Instead, IANA allocates massive blocks of IP addresses to five Regional Internet Registries (RIRs). These are non-profit, membership-based organizations responsible for managing IP allocation within their specific geographic region. ISPs, enterprises, and cloud providers apply to their regional RIR for address space.
The Five RIRs:
| RIR | Full Name | Region |
|---|---|---|
| ARIN | American Registry for Internet Numbers | North America, parts of the Caribbean |
| RIPE NCC | Réseaux IP Européens Network Coordination Centre | Europe, Middle East, Central Asia |
| APNIC | Asia Pacific Network Information Centre | Asia and the Pacific |
| LACNIC | Latin American and Caribbean Internet Addresses Registry | Latin America and the Caribbean |
| AFRINIC | African Network Information Centre | Africa |
The allocation chain works like this: IANA allocates a large block (e.g., 104.0.0.0/8) to ARIN. ARIN then allocates a smaller block (e.g., 104.16.0.0/12) to a large ISP like Cloudflare. Cloudflare then assigns individual IPs from that block to its infrastructure. Your home router gets a single IP from your ISP's allocation.
RIRs also maintain WHOIS databases — publicly queryable registries that record who owns which IP block. This is how network engineers, security researchers, and abuse teams can look up the owner of any IP address on the internet.
IPv4 Exhaustion: IANA allocated its last IPv4 blocks to the RIRs in February 2011. Most RIRs have since exhausted their free IPv4 pools as well. Today, new IPv4 addresses are primarily obtained through a secondary market (buying blocks from organizations that no longer need them), which can cost thousands of dollars per address. This is a major driver of IPv6 adoption.
Interviewers sometimes ask: "Who owns the internet?" or "Who controls IP address allocation?" The correct answer involves the IANA → RIR → ISP hierarchy. A common mistake is saying "ICANN controls IP addresses" — ICANN is the organization that operates the IANA function, but the RIRs are the ones doing regional allocation. Distinguish between ICANN (policy and DNS), IANA (the technical function), and RIRs (regional IP distribution).
Key Point: RIRs are the operational layer between IANA's global pool and the ISPs that need addresses. With IPv4 exhaustion complete, RIRs now primarily manage transfers and waiting lists, making IPv6 adoption increasingly critical.