What Is ARIN (American Registry for Internet Numbers)?
ARIN, the American Registry for Internet Numbers, is a nonprofit, member-based organization that administers IP addresses and Autonomous System Numbers (ASNs) in support of the operation and growth of the Internet. It matters to you if you need IPv4 or IPv6 address space, an ASN for network routing, or want to look up who holds a given block of addresses. ARIN serves the United States, Canada, and many Caribbean and North Atlantic islands.
What ARIN actually does
ARIN is a Regional Internet Registry (RIR). Its core job is to allocate and assign Internet number resources — IP addresses and ASNs — to organizations in its service region, and to maintain the public registry that records who holds those resources.
The main work breaks down into a few areas:
- IP address management — IPv4 and IPv6 allocations and assignments, including IPv4 addressing options and IPv6 information.
- ASN administration — issuing Autonomous System Numbers used for routing between networks.
- Registry services — managing resource records, transfers of IP addresses and ASNs, and reporting reassignments.
- Routing security — Resource Public Key Infrastructure (RPKI), the Internet Routing Registry (IRR), and DNSSEC-related services.
- Policy and participation — the Number Resource Policy Manual, the Policy Development Process, and public policy and members meetings.
Who ARIN serves
ARIN's region covers the United States, Canada, and a number of Caribbean and North Atlantic islands. If your network operates in that region and you need address space or an ASN, ARIN is the registry you deal with. Organizations elsewhere fall under a different RIR.
How to get started with ARIN
The site organizes the practical path under "Get Started," which covers:
- ARIN Account Management — setting up and managing your account.
- Requesting IP Addresses or ASNs — submitting requests for resources.
- IPv6 Information and IPv4 Addressing Options — choosing which address family and approach fits your needs.
- Fee & Billing Information — the fee schedule, how billing works, and payment options.
ARIN also provides reference tools such as a CIDR Calculator, an Operational Test and Evaluation (OT&E) environment, and a Community Software Repository.
Beyond allocation: registry data and security
ARIN maintains several services that matter once you hold resources:
- Whois and registry data — searching IP addresses and ASNs, plus data accuracy and historical Whois data (WhoWas).
- Routing security — RPKI, IRR, and reverse DNS.
- Fraud and abuse reporting — Internet number resource fraud reporting and spam/network abuse reporting.
Membership and governance
ARIN is member-based. Its structure includes a Board of Trustees, an Advisory Council, and the NRO Number Council, with membership elections and community interaction through mailing lists, consultations, and surveys. Corporate documents, annual reports, and strategic planning materials are published publicly.
Quick reference
| Question | Answer |
|---|---|
| What is ARIN? | A nonprofit, member-based Regional Internet Registry |
| What does it manage? | IP addresses and ASNs |
| Who does it serve? | US, Canada, and parts of the Caribbean/North Atlantic |
| How do you request resources? | Through ARIN Account Management and the request process |
| Where are fees? | Fee Schedule and Fee & Billing Information pages |
If you operate a network in ARIN's region and need address space or an ASN, start with account management and the request process; if you only need to look up who holds a resource, the Whois search is the entry point.