What is ARIN?
ARIN is the American Registry for Internet Numbers, the nonprofit Regional Internet Registry that administers Internet number resources in its service region. It distributes and registers IPv4 address space, IPv6 address space, and Autonomous System Numbers (ASNs) under policies developed by the ARIN community.
ARIN is one part of a global registry system. IANA coordinates the global pools and makes high-level allocations to the five Regional Internet Registries. ARIN then evaluates requests, maintains registration data, and provides related registry services for its region. An ISP can also provide address space to a customer from the ISP's allocation, so not every organization needs resources issued directly by ARIN.
For the global hierarchy and the other four registries, see the Regional Internet Registry guide.
What region does ARIN serve?
ARIN serves Canada, the United States, and many Caribbean and North Atlantic economies. Geography alone does not guarantee eligibility for a particular request. The requesting legal entity and the network using the resources must satisfy the current policy and documentation requirements for the request type.
Check ARIN's current service-region list before planning a direct request or transfer. Organizations operating elsewhere normally work with the RIR responsible for that region, although approved inter-RIR transfers can involve more than one registry.
What number resources does ARIN manage?
| Resource | What ARIN records or issues | What the resource does not provide by itself |
|---|---|---|
| IPv4 address space | Registered IPv4 allocations and assignments under current policy, including approved transfers | A live BGP route, clean reputation, application acceptance, or unlimited supply |
| IPv6 address space | IPv6 allocations and assignments sized under applicable policy | Automatic deployment, routing, DNS, firewall policy, or IPv4 compatibility |
| Autonomous System Number | A unique public ASN when the request qualifies | A network, upstream connection, routing policy, or authority to originate someone else's prefix |
ARIN distinguishes an allocation, commonly made to a provider for further distribution, from an assignment intended for an organization's own network use. The exact definitions and eligibility rules come from the current Number Resource Policy Manual. Learn how an ASN participates in routing in the Autonomous System Number guide.
Does ARIN assign IP ranges?
Yes. ARIN can issue IP address ranges to qualified organizations in its region, but the available path depends on the resource and current policy. It continues to issue IPv6 space and ASNs. ARIN's general-purpose IPv4 free pool was depleted on 24 September 2015, so a normal request no longer means that plentiful IPv4 space is available on demand.
Organizations seeking IPv4 space may qualify for a limited reserved policy pool or waiting-list distribution, receive provider-assigned space from an ISP, obtain space through an ARIN-approved transfer, or use a contractually authorized lease. Each path has different registry, routing, cost, continuity, and return implications. Availability and approval are never guaranteed.
A direct ARIN registration is not the same as a local DHCP assignment. ARIN works with public Internet number resources; a router or address-management system assigns addresses to interfaces inside a network. The IP address allocation guide separates the registry and local-network layers.
How do you look up an ARIN IP address or range?
Use ARIN's Registration Data Access Protocol (RDAP) service to search an IP address, CIDR prefix, ASN, or public registry entity. RDAP is the standardized, machine-readable successor to traditional Whois query access. A query can identify the registered network range containing an address and expose the public registration data available for that record.
- Normalize the query. Record the exact IPv4 or IPv6 address, CIDR prefix, or ASN and the observation time.
- Use the authoritative bootstrap path. Start with ARIN's RDAP search; if another RIR is authoritative, follow the referral rather than assuming ARIN owns the record.
- Read the network object. Check the range, CIDR, handle, status, parent relationship, registration dates, organization, and public contacts.
- Corroborate operational facts. Check current BGP visibility, origin ASN, RPKI state, IRR objects, reverse DNS, reputation observations, and the counterparty's contractual authority separately.
| Field or result | Useful meaning | Important limit |
|---|---|---|
| Network range and CIDR | The registry object that contains the queried address or prefix | Does not show that the entire range is currently routed or offered to a customer |
| Organization and handle | The entity and identifier associated with the registration | Is not conclusive proof of legal title, present control, or authority for a proposed transaction |
| Status and parent | The registry classification and relationship to a larger block | Does not replace review of the applicable policy, agreement, or downstream assignment |
| POC or contact role | Public administrative, technical, routing, or abuse contact data when published | May be role-based, redacted, stale, or different from the person negotiating a service |
| Registration event dates | When the public object records creation or a later change | Do not reveal every operational, routing, lease, or reputation event |
Registry data is evidence about registration, not a complete ownership or safety verdict. For a transaction, preserve the RDAP response and date, verify the contracting entity, and document how that entity is authorized to provide or transfer the exact prefix.
ARIN vs IANA, an ISP, and an IPv4 provider
| Party or system | Primary role | Question it can answer |
|---|---|---|
| IANA | Coordinates global IP address and ASN pools and makes high-level allocations to RIRs | Which registry system is responsible for a resource? |
| ARIN | Administers number resources and public registration services in the ARIN region | What does the authoritative registry record, and does a request meet current ARIN policy? |
| ISP or upstream | Provides connectivity, may assign customer addresses, and applies route filters | Which prefixes and origins will this network accept and carry? |
| Seller, lessor, or broker | Offers a commercial transfer, lease, or facilitation service | What contractual right, term, price, support, and exit process are being offered? |
| BGP, RPKI, and IRR | Publish or validate different routing signals | What route is observed, what origin is authorized by a ROA, and what routing policy is registered? |
No single row replaces the others. A clean-looking registry record does not create a route; a visible BGP route does not prove commercial authority; and an approved registry transfer does not guarantee reputation, geolocation, deliverability, or application acceptance.
How do you request resources from ARIN?
A direct request normally starts in ARIN Online. The organization needs a valid Organization Identifier and appropriate Points of Contact, then submits the resource-specific request and evidence required by current policy. ARIN reviews qualification, documentation, fees, and the applicable registration agreement before approved resources are issued.
- Confirm that the legal entity and intended resource use fall within ARIN's service region.
- Create or recover the correct ARIN Online account, POC records, and Organization Identifier.
- Select the IPv6, ASN, IPv4 waiting-list, reserved-pool, or transfer path that matches the real need.
- Prepare the network plan and supporting records requested by the current policy; do not manufacture utilization or routing evidence.
- Budget for published fees and ongoing registry maintenance, and name owners for contacts, security, routing, DNS, and renewals.
Start with ARIN's requesting Internet number resources guide and verify the current policy before submitting. The IPv4 acquisition guide compares direct registry, provider, transfer, purchase, and lease routes.
How do ARIN IPv4 transfers work?
ARIN policy supports several transfer categories, including transfers tied to mergers or acquisitions, specified-recipient transfers within the ARIN region, and compatible inter-RIR transfers. The parties use ARIN Online, maintain valid organization and contact records, submit the required evidence, and complete ARIN's review before the registry changes are finalized.
A private sale agreement and a registry transfer are related but distinct. ARIN applies policy and updates registry records; the parties remain responsible for commercial terms, legal diligence, payment controls, routing migration, RPKI and IRR changes, reverse DNS, reputation, abuse handling, and service continuity. Review ARIN's current transfer guidance rather than assuming every block or counterparty is eligible.
Does ARIN provide or approve IPv4 leasing?
ARIN is a registry, not an IPv4 leasing marketplace. A lease is a contract granting time-limited use under agreed conditions; it is not automatically a registry allocation, assignment, or transfer. An ARIN registration may continue to name the resource holder while another party is authorized to use or announce some or all of the space.
Before leasing a prefix, verify the lessor's authority, exact CIDR, term, route and origin model, Letter of Authorization where applicable, RPKI and IRR responsibilities, reverse DNS, geolocation, reputation evidence, abuse contacts, renewal, replacement, return, and renumbering plan. Compare these controls in the IPv4 leasing guide or submit the evidence for managed IPv4 leasing.
What do ARIN RPKI, IRR, and reverse DNS services show?
- RPKI and ROAs: A Route Origin Authorization is a signed object stating that a specified ASN is authorized to originate a prefix, subject to its maximum length. It does not prove ownership, a lease, current BGP visibility, or complete protection from route hijacking.
- Internet Routing Registry: IRR route and related objects describe routing policy used by some networks to build filters. They are separate from public registration data and do not prove that a route is currently visible or cryptographically valid.
- Reverse DNS: Delegation lets the responsible operator publish PTR records for addresses. It is separate from forward DNS, routing, registry authority, and reputation.
- Registration maintenance: Organization and POC records need current, authorized contacts. Stale public data can delay incident response, transfers, resource requests, and operational coordination.
Use ARIN's ROA guidance and IRR guidance for the current workflows. For any production prefix, record who owns each update, what evidence confirms it, and how changes are rolled back.
ARIN resource due-diligence checklist
- Registry: Save the authoritative RDAP object, exact prefix, organization, parent, status, contacts, and evidence date.
- Authority: Match the registry holder and contracting party; document any agency, downstream assignment, LOA, lease, or transfer authority.
- Policy: Confirm the current ARIN policy path, service region, eligibility, fees, agreements, and required records.
- Routing: Verify expected origin ASN, upstream acceptance, observed BGP, ROA coverage and maximum length, IRR objects, and failover.
- Operations: Assign owners for reverse DNS, geolocation, monitoring, reputation, abuse response, incident evidence, and contact maintenance.
- Lifecycle: Define activation, renewal, transfer or return, renumbering, data retention, and rollback before production use.
The IP risk assessment guide turns these registry and routing facts into a dated workload decision.
ARIN FAQ
What does ARIN stand for?
ARIN stands for the American Registry for Internet Numbers. It is the nonprofit Regional Internet Registry that administers IPv4, IPv6, and ASN resources in its service region under community-developed policy.
What countries and economies does ARIN cover?
ARIN serves Canada, the United States, and many Caribbean and North Atlantic economies. Because the list and transfer relationships matter to eligibility, verify the current service-region page rather than relying on an abbreviated country list.
Does ARIN assign IP addresses and ranges?
Yes. ARIN can issue public IP address space to qualified organizations under current policy. IPv6 remains available through applicable request paths, while the general-purpose IPv4 free pool was depleted in 2015 and IPv4 now follows limited waiting-list, reserved-pool, provider, or transfer paths.
Can ARIN tell me who owns an IP address?
ARIN RDAP can show the public organization and network registration associated with an address in its registry. That record is useful evidence, but it is not by itself conclusive proof of legal title, present control, a lease, the user behind an address, or authority for a proposed transaction.
Is ARIN the same as IANA or ICANN?
No. IANA coordinates the global number-resource pools and makes high-level allocations to Regional Internet Registries. ARIN is one of those five RIRs and administers resources within its service region. ICANN has a broader coordination role and is not a substitute for the relevant RIR.
Can I buy or lease IPv4 addresses from ARIN?
ARIN does not operate an IPv4 sales or leasing marketplace. It reviews eligible resource requests and transfers and maintains registry services. Commercial purchases and leases require separate counterparties, contracts, authority checks, routing plans, and operational diligence.
Does a ROA prove ownership or prevent every route hijack?
No. A ROA states which origin ASN is authorized for a prefix and maximum length. Networks can use Route Origin Validation as one routing control, but a ROA does not prove ownership or contractual authority, show that a route is live, or prevent every routing incident.
How do I search an ARIN IP address or CIDR?
Use ARIN's RDAP search with the exact address or prefix. Follow any referral to the authoritative RIR, preserve the response and date, then check BGP, RPKI, IRR, DNS, contractual authority, and reputation as separate evidence.
