IPv4 Addresses Have Been "Exhausted" - Yet They're Being Bought and Sold

IP address exhaustion is one of the greatest structural challenges in internet history. IPv4 addresses are 32-bit, meaning only about 4.3 billion exist. For a comprehensive overview of how IP addresses work and why they matter, see our guide on what an IP address is. When IPv4 was standardized in RFC 791 in 1981, 4.3 billion seemed like an astronomical number. However, the explosive growth of smartphones, IoT devices, and cloud services led to the official depletion of IANA's (Internet Assigned Numbers Authority) unallocated address pool in February 2011.

Yet the internet keeps running. Why? The answer lies in technical stopgap measures and a market where IP addresses are bought and sold like real estate.

Where Did 4.3 Billion Addresses Go?

Looking back at the history of IPv4 address allocation reveals just how generous the early distributions were.

Massive Class A Blocks

In the early days of the internet, IP addresses were allocated in units of Class A (/8, approximately 16.77 million addresses), Class B (/16, approximately 65,536), and Class C (/24, 256). Entire Class A blocks were assigned to organizations such as:

  • MIT (18.0.0.0/8) - approximately 16.77 million addresses
  • Apple (17.0.0.0/8) - approximately 16.77 million addresses
  • Ford Motor Company (19.0.0.0/8) - approximately 16.77 million addresses
  • US Department of Defense - holding multiple Class A blocks
  • General Electric (3.0.0.0/8) - approximately 16.77 million addresses

While a single organization held 16.77 million IP addresses, there was a time when the entire African continent had fewer addresses than MIT alone. This early allocation imbalance was a contributing factor to the exhaustion problem.

Regional Exhaustion Timeline

  • February 2011: IANA's central pool exhausted. The last five /8 blocks were distributed one each to the five RIRs (Regional Internet Registries)
  • April 2011: APNIC (Asia-Pacific) ended normal allocations. The Asia-Pacific region, including Japan, was the first to exhaust
  • September 2012: RIPE NCC (Europe) reached its last block
  • June 2014: LACNIC (Latin America) exhausted
  • September 2015: ARIN (North America) exhausted. Introduced a waiting list system
  • April 2017: AFRINIC (Africa) approached exhaustion as the last region

Stopgap Measures - NAT, CGNAT, and the Age of "Sharing"

The biggest reason the internet continues to function despite IPv4 exhaustion is NAT (Network Address Translation).

NAT - Sharing One IP Address with the Family

Your home router shares the single global IP address assigned by your ISP among multiple household devices (smartphones, PCs, tablets, IoT devices). Each device is assigned a private IP address (such as 192.168.x.x), and the router performs address translation.

The IP address you see on IP Check-san is your router's global IP address. No matter which device in your home you use to access it, the same IP address will be displayed.

CGNAT - Large-Scale Sharing at the ISP Level

CGNAT (Carrier-Grade NAT) applies NAT on a much larger scale. An ISP places hundreds to thousands of customers behind a single global IP address. This means you might be sharing an IP address with your neighbors.

While CGNAT is effective at conserving IP addresses, it causes several problems:

  • GeoIP accuracy degradation: Users from different regions share the same IP address
  • IP-based access restriction false positives: One malicious user can get everyone sharing the same IP blocked
  • Connection issues with P2P communications and online gaming
  • Difficulty for law enforcement in identifying individuals: An IP address alone cannot identify a person

The IPv4 Address Market - Digital Real Estate

Exhausted IPv4 addresses have acquired real economic value. Unused IPv4 address blocks are bought and sold through specialized brokers.

Price Trends

The per-address transaction price for IPv4 addresses has fluctuated with supply and demand.

  • Around 2014: approximately $7-10 per address
  • Around 2018: approximately $15-20 per address
  • 2021 (peak): approximately $50-60 per address
  • 2024 onward: trending slightly downward to around $30-40 as IPv6 adoption grows

Holding a /16 block (65,536 addresses) means an asset worth several million dollars. MIT reportedly sold half of its /8 block (approximately 8 million addresses) in 2017, generating hundreds of millions of dollars in revenue.

Notable Transactions

  • Microsoft: Purchased approximately 666,624 IPv4 addresses from Nortel Networks' bankruptcy proceedings in 2011 for about $7.5 million (approximately $11.25 per address)
  • Amazon: Acquired large quantities of IPv4 addresses from the market to support AWS's rapid growth. AWS began charging $3.60 per month per public IPv4 address in 2024
  • MIT, Stanford, BBN: Sold portions of their large blocks allocated in the early days, using proceeds for research funding

IPv6 - Why the Real Solution Is Slow to Adopt

IPv6 has a 128-bit address space, providing approximately 340 undecillion (3.4 × 10^38) addresses. That's enough to assign an IP address to every grain of sand on Earth with plenty to spare. The IPv6 specification was finalized in 1998, yet as of 2025, global IPv6 adoption remains at only about 40-45%.

Why Adoption Is Slow

  • No backward compatibility with IPv4: IPv6 cannot communicate directly with IPv4. Dual-stack (running both simultaneously) is required, making migration costly
  • NAT works "well enough": NAT and CGNAT keep the internet running on IPv4. The motivation to "fix what isn't broken" is weak
  • Legacy systems: Older network equipment, software, and firewall rules don't support IPv6
  • Lack of operational expertise: Many network engineers are well-versed in IPv4 operations but have limited IPv6 experience

IPv6 Adoption in Japan

Japan is one of the world's leaders in IPv6 adoption, with over 50% of users connecting via IPv6 according to Google's statistics. A major factor is NTT's FLETS Hikari offering IPv6 IPoE (MAP-E/DS-Lite) as standard. Check on IP Check-san whether your connection is IPv4 or IPv6.

Summary - The Battle for 4.3 Billion Addresses Continues

IPv4 address exhaustion is a structural problem brought about by growth on a scale the internet's designers never imagined in 1981. Three forces are progressing in parallel: life extension through NAT and CGNAT, the IPv4 address trading market, and gradual migration to IPv6.

Whether the IP address shown on IP Check-san is IPv4 or IPv6, whether you're behind CGNAT, and what history that address carries - behind the IP address you use every day without a second thought lies a world where technology, economics, and politics are deeply intertwined.

Related Terms

IP Address A numerical address that identifies devices on the internet. Comes in two types, IPv4 and IPv6, used to specify communication endpoints. IPv6 The next-generation internet protocol with a 128-bit address space. Provides approximately 340 undecillion addresses compared to IPv4's roughly 4.3 billion. NAT (Network Address Translation) A technology that translates between private and global IP addresses. Enables multiple devices to share a single global IP. ISP (Internet Service Provider) A company that provides internet connectivity to individuals and businesses. Connection types, speeds, and pricing vary by ISP. CIDR A notation for efficient IP address allocation and route aggregation. Expresses network size using prefix lengths like /24 or /16.