What Is ARIN: All You Need To Know

3 min read
12 November 2021

The American Registry for Internet Numbers is an essential body in the architecture of today's Internet. Keep reading to learn more about this Regional Internet Registry.

Service region of the American Registry for Internet Numbers on map.

The American Registry for Internet Numbers (ARIN) is the primary nonprofit corporation that manages the registration of numerous blocks of IP addresses to North American Internet Service Providers (ISPs). More specifically, it does this in the US, Canada, Antarctica and many islands of the Caribbean.

ARIN is one of five Regional Internet Registries (RIRs) in the world that work with ISPs in their specific regions. The other four RIRs and their respective areas of service are:

Regional internet registry regions on a map.
The service regions of 5 Regional Internet Registries

Now that you know what this critical nonprofit organization is, let’s look at what it does. 

What does ARIN do?

The primary function of any Regional Internet Registry is registering IP addresses and Autonomous System Numbers (ASNs). While IANA, or the Internet Assigned Numbers Authority, acts as the primary administrator of IP addresses worldwide, RIRs are responsible for IP resources in specific regions.

ARIN is responsible for providing internet numbers to local internet registries (usually ISPs) and internet users in the regions it covers. 

The regions that the American Registry for Internet Numbers serves include several sectors with their own countries and dependent territories:

  • The Canadian sector: Canada
  • The Caribbean and North Atlantic islands sector: around 20 island countries and territories like Jamaica, Bahamas and St. Lucia
  • The outlying areas sector: St. Helena, Bouvet Island, Heard and McDonald Islands, and Antarctica
  • The United States sector: the United States, Puerto Rico, US Minor Outlying Islands and the Virgin Islands

Besides the registration of internet numbers, resource organization and policy development, ARIN also ensures it offers directory lookup services to the public, like the Whois and WhoWas services. 

Furthermore, ARIN provides various technical services, including technical training and education within the internet community. 

ARIN registration services

The IP registration services from the American registry include the allocation, assignment and transfer of three types of internet number resources:

  • IPv4 addresses
  • IPv6 addresses
  • ASN numbers
Examples of IPv4 and IPv6 addresses and an ASN number.
ARIN manages the registration of IP addresses and ASNs in its service region

Besides the allocation, transfer and assignment of internet numbers, the work of the American registry further includes:

History of ARIN

In the early days of the internet, the current system with Regional Internet Registries wasn’t necessary. Simply because there weren’t as many internet number resources as there are today. For a time, it was even enough for one man to perform the job of the entire IANA, plus the five regional registries. 

However, by the 1990s, the internet grew enough to make IP registration tasks much more cumbersome. Additional management was necessary. As a result of that, in 1992, the concept of a Regional Internet Registry was created. RIPE NCC was the first RIR to start operating. 

Timeline of when 5 RIRs were established.
The timeline of RIRs’ establishment

ARIN’s history begins later as this specific RIR was formed on December 22, 1997. Before ARIN took over the various tasks surrounding IP numbers, the regions that ARIN manages today were governed according to the policies set by the Internet Engineering Task Force

When ARIN began, it was established in Virginia, where its headquarters remain today. The Executive Board also started operating with the responsibility of acting as the governing body of ARIN. The current chair is Paul Andersen, and the President and CEO is John Curran

Interestingly, the American registry served more regions in the past, but that changed twice, first in 2002 and then in 2005. LACNIC took over South America, Central America, Mexico and parts of the Caribbean in 2002, and AFRINIC took over Sub-Saharan Africa in 2005. 

In 2015, ARIN declared that it had exhausted its pool of IPv4 addresses, which is just one of the many instances that clearly illustrate the problem of IPv4 exhaustion


The American Registry for Internet Numbers is an integral part of the modern internet ecosystem. Being one of the five Regional Internet Registries globally, it plays a vital role in the allocation, assignment and transfer of all internet numbers for its region. Without ARIN, ISPs couldn’t assign IP numbers in the same seamless way they currently do.

As long as the American Registry for Internet Numbers is here to provide IP registration services and all other organizational, policy-making and education tasks it offers, the internet on the North American continent will continue functioning like a well-oiled machine.

About the author

Edvinas Račkauskas

Business Analyst

Edvinas is a Business Analyst at IPXO. Besides providing his insights into the IPv4 market, Edvinas specializes in internet governance, specifically Regional Internet Registries’ policies and regulations. During his free time, Edvinas enjoys exploring new places and travelling to exotic lands.
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