Running out of IPv4 addresses means the internet has no more new numbers to give out. Every device connected to the internet needs a unique number called an IP address. The supply of these numbers has been exhausted. This guide explains why running out of IPv4 addresses happened, how the internet still works, and what the future holds.
What Are IPv4 Addresses?
IPv4 stands for Internet Protocol version 4. Engineers introduced this addressing system in the early 1980s. Every IPv4 address looks like four numbers separated by dots – for example, 192.168.1.1. Think of it as a postal address for your computer, phone, or smart TV. Without it, data packets would not know where to go.
Why Every Device on the Internet Needs an IP Address
When you visit a website or send an email, your device attaches its IP address to every data packet. The receiving server uses that address to send a reply. If every device needed a unique public address, the system would need as many addresses as there are connected devices. That is why running out of IPv4 addresses became such a serious problem.
Total Number of IPv4 Addresses: The 4.3 Billion Limit
An IPv4 address is 32 bits long. That gives exactly 4,294,967,296 possible addresses – about 4.3 billion. To put that in perspective: there are fewer IPv4 addresses than people on Earth (nearly 8 billion). Roughly 600 million of those 4.3 billion are reserved for special purposes. They cannot be used for normal internet communication. So the usable pool is even smaller.
Why Engineers Thought 4.3 Billion Was Enough
When engineers designed IPv4 in the late 1970s, the internet was a tiny research network. It connected only a few hundred computers at universities and military labs. One of IPv4’s creators, Vint Cerf, later admitted: “Who the hell knew how much address space we needed?” At that time, 4.3 billion addresses felt like an infinite supply. No one predicted running out of IPv4 addresses would happen within their lifetimes.
The Growth of the Global Internet Population
The internet’s user base exploded from a few thousand researchers in the 1980s to over five billion people today. Each new user needs at least one IP address for their primary device. This growth alone would have consumed IPv4 addresses eventually. Running out of IPv4 addresses became inevitable as the internet went global.
The Explosion of Smartphones and Tablets
In the 1980s, only mainframes and research computers needed IP addresses. Today, billions of smartphones, laptops, smartwatches, and tablets compete for the same pool. Nearly every person in the developed world carries at least one connected device in their pocket. This explosion accelerated running out of IPv4 addresses dramatically.
The Rise of Smart TVs, Cameras, and IoT Devices
The number of connected IoT devices reached approximately 21.1 billion by the end of 2025. Smart meters, security cameras, smart speakers, thermostats, and even refrigerators all need IP addresses. By 2030, that number is projected to approach 39 billion. Each new device makes running out of IPv4 addresses more visible.
Cloud Computing and Datacenter Growth
Amazon Web Services (AWS), Microsoft Azure, and Google Cloud have built massive networks with millions of servers. Each server needs public IP addresses. Cloud providers hold millions of purchased IPv4 addresses. Their growth is another major reason why running out of IPv4 addresses happened so fast.
The Multiple Devices per Household Problem
A single household might easily contain a dozen connected devices: phones, laptops, tablets, smart TVs, gaming consoles, smart speakers, security cameras, smart lights, and more. The internet was never designed to handle this level of demand from individual households. This everyday reality hides the severity of running out of IPv4 addresses.
Early Wasteful IP Allocations in the 1980s
In the early internet, engineers used a system called classful networking. The table below shows how inefficient that system was.
| Class | Address Range | Hosts per Network | Problem |
|---|---|---|---|
| A | 1.0.0.0 – 126.0.0.0 | 16.8 million | Too large for most organizations |
| B | 128.0.0.0 – 191.255.0.0 | 65,534 | Often wasted thousands of addresses |
| C | 192.0.0.0 – 223.255.255.0 | 254 | Too small for medium companies |
| D | 224.0.0.0 – 239.255.255.255 | – | Multicast only |
| E | 240.0.0.0 – 255.255.255.255 | – | Reserved for experiments |
If an organization needed 1,000 IP addresses, a Class C (254 addresses) was too small, but a Class B (65,534 addresses) wasted 64,000 addresses. Many large companies received Class B allocations when they needed far less. These wasteful allocations sped up running out of IPv4 addresses considerably.
Class A Network Allocations Explained Simply
Class A networks were the largest blocks of IPv4 addresses. Each Class A block contained over 16.8 million IP addresses. These blocks were given out freely to universities and companies in the 1980s and 1990s.
Universities and Companies That Received Huge IP Blocks
Many large American institutions received entire Class A blocks. These included MIT, Stanford University, Apple, IBM, Boeing, Ford, and Halliburton. The Department of Defense owned multiple Class A blocks as well. Together, the 126 existing Class A blocks hold over 671 million IP addresses. That is one reason running out of IPv4 addresses happened faster than necessary.
Why IPv4 Addresses Cannot Simply Be Expanded
IPv4 is built on a 32-bit address system. Expanding this to a larger format would break compatibility with every existing device, router, and piece of networking software on the internet. This is why engineers created an entirely new protocol instead of trying to patch IPv4. Once you understand this, running out of IPv4 addresses makes sense as a design constraint, not a mistake.
The Difference Between Public and Private IP Addresses
Public IP addresses are globally unique and routable on the internet. Private IP addresses are not globally unique. The same private addresses can appear simultaneously inside millions of different homes, offices, and datacenters. Private addresses are not routable on the public internet. This distinction helped delay running out of IPv4 addresses for many years.
How NAT Helped Slow Down the Shortage
Network Address Translation (NAT) became the most important technology that kept the internet running after running out of IPv4 addresses became inevitable. NAT allows an entire home or office network to share a single public IPv4 address. All devices inside the network use private IP addresses, and the router translates between the private addresses and the single public address when communicating with the outside world.
What CGNAT Is and Why ISPs Use It
As home routers began sharing single public IPs, internet service providers (ISPs) faced the same problem: not enough public IPv4 addresses to give each customer a unique one. Carrier‑Grade NAT (CGNAT or NAT444) adds an extra layer of NAT inside the ISP’s network. Your home router does its normal NAT, translating your private device IPs into a private ISP‑assigned address. Then, deeper in the carrier’s network, another NAT device translates that private ISP address into one of a much smaller pool of public IPv4 addresses. With CGNAT, a single public IPv4 address can serve over 100 customers simultaneously. CGNAT is a direct consequence of running out of IPv4 addresses.
Why Mobile Carriers Consume Massive Numbers of IP Addresses
Mobile carriers were among the first to feel the squeeze. CGNAT techniques first appeared commercially in 2000 to support GPRS (2.5G) mobile data. Today, nearly every mobile carrier uses CGNAT to serve millions of subscribers from a small pool of public IPv4 addresses. Mobile data growth accelerated running out of IPv4 addresses significantly.
The Role of IANA and Regional Internet Registries
Two main bodies manage global IP address distribution. IANA (Internet Assigned Numbers Authority) oversees the central pool of IP addresses. IANA allocates large blocks of IPv4 addresses to the five Regional Internet Registries (RIRs).
| RIR | Region Covered | Depletion Date |
|---|---|---|
| APNIC | Asia Pacific | April 2011 |
| LACNIC | Latin America and Caribbean | June 2014 |
| ARIN | USA, Canada, parts of the Caribbean | September 2015 |
| RIPE NCC | Europe, Middle East, Central Asia | Late 2026 (projected) |
| AFRINIC | Africa | Not yet fully exhausted |
When IANA allocated the last batch of IPv4 addresses to the five RIRs on 3 February 2011, the world officially began running out of IPv4 addresses at the top level.
Timeline of IPv4 Exhaustion Worldwide
Here is the complete timeline of the shortage.
| Date | Event |
|---|---|
| Late 1980s | Engineers first warn of potential shortage |
| 3 February 2011 | IANA exhausts its central pool – official start of running out of IPv4 addresses globally |
| 15 April 2011 | APNIC (Asia Pacific) exhausts its free pool |
| 10 June 2014 | LACNIC (Latin America) exhausts its free pool |
| 24 September 2015 | ARIN (North America) exhausts its free pool |
| Late 2026 | RIPE NCC (Europe) expects to exhaust its last remaining addresses |
| Still limited | AFRINIC (Africa) remains the only RIR with a remaining free pool |
When IANA allocated the last batch, Rod Beckstrom, president and CEO of ICANN, said: “A pool of more than 4 billion Internet addresses has just been emptied this morning – completely depleted.”
Why the Shortage Did Not Break the Internet
IPv4 addresses continue to work normally because the shortage only affects free unallocated addresses, not addresses already assigned to organizations. The pool of allocated addresses – over 4 billion – remains fully operational. Even with IANA and RIR pools empty, IPv4 addresses still circulate through transfers and leases. Organizations that no longer need their IPv4 blocks can sell or lease them to others. This recycling is why running out of IPv4 addresses did not cause an immediate internet collapse.
IPv4 Recycling and Reuse
Because no new IPv4 addresses are available, organizations must now reuse existing addresses. When a company goes out of business or no longer needs its IPv4 allocation, those addresses can be returned to a registry or sold to another organization. This recycling keeps the internet running despite running out of IPv4 addresses.
The IPv4 Buying, Selling, and Leasing Market
Once the free pools dried up, a secondary market for IPv4 addresses emerged. This market is now a billion‑dollar industry.
Price Evolution Over Time
- Around 2011: 5to10 per IP
- Around 2015: 5to10 per IP (stable)
- Around 2021: 40to50 per IP
- 2026 (current): 35to60 per IP, varying by region and block size
A /24 block (256 addresses) typically sells for 6,000to15,000. A single /16 block (65,536 addresses) that cost nothing in the 1990s is now worth over 1.5 million. The annual global transfer market volume reaches an estimated 1.2 billion. High prices are a direct symptom of running out of IPv4 addresses.
How Companies Lease IPv4 Addresses
Leasing has become a popular alternative to outright purchase. Monthly leasing rates typically range from 0.38 to 0.75 per IP.
Security Issues Caused by the Shortage
Running out of IPv4 addresses has created new security risks. Let us look at the three most dangerous ones.
BGP Hijacking
The Border Gateway Protocol (BGP) is the internet’s routing system. Because IPv4 addresses have become scarce and valuable, attackers increasingly announce false routes for IP blocks they do not own. This technique, called BGP hijacking, diverts traffic meant for a legitimate destination to the attacker’s network. When scarcity pushes prices high, a successfully hijacked block gives the attacker control of millions of dollars worth of routing space.
IPv4 Transfer and Lease Market Abuse
Scarce, tradable IPv4 addresses have also attracted fraud. In February 2025, leased IPv4 prefixes were 2.89 times more likely to be flagged by blocklists compared to non‑leased prefixes. Sold or leased blocks are sometimes used for malicious campaigns – spam, malware distribution, DDoS attacks, or botnet command‑and‑control – after the deal closes.
IP Reputation Issues
Spam accounts for roughly 66% of reported IPv4 abuse cases. Malware follows at 14%, and DDoS attacks at 4%. When a legitimate organization leases its IP block to an abuser, the entire block’s reputation may suffer.
Why IPv6 Was Created
Engineers created IPv6 specifically to solve running out of IPv4 addresses. The Internet Engineering Task Force recognized the coming shortage as early as the late 1980s and began designing IPv6 in the 1990s.
IPv4 vs. IPv6 Comparison
| Feature | IPv4 | IPv6 |
|---|---|---|
| Address length | 32 bits | 128 bits |
| Total number of addresses | ~4.3 billion | 340 undecillion |
| Address format example | 192.0.2.1 | 2001:0db8:85a3:0000:0000:8a2e:0370:7334 |
| NAT required | Yes (almost always) | No |
| Security | Optional IPsec | Mandatory IPsec support |
| Configuration | Manual or DHCP | SLAAC (automatic, stateless) |
| Packet header | 20–60 bytes, variable | 40 bytes, fixed, simpler for routers |
IPv6 provides 340 undecillion addresses – enough to assign multiple IP addresses to every atom on the Earth’s surface. Engineers often say IPv6 could assign an IP address to every grain of sand on every beach on the planet. IPv6 is the permanent solution to running out of IPv4 addresses.
Why IPv6 Adoption Is Slow
Despite being designed over 25 years ago, IPv6 adoption has been slow. Global IPv6 usage crossed 50% for the first time on 28 March 2026.
Global IPv6 Adoption by Country (2026)
| Country | IPv6 Adoption Rate |
|---|---|
| France | ~86% |
| Germany | ~77% |
| India | ~75% |
| United States | ~55% |
| Russia | ~48% |
| China | ~5% |
Causes of Slow Adoption
NAT worked “well enough” – For many years, NAT reduced urgency around running out of IPv4 addresses.
Migration costs – Upgrading routers, firewalls, load balancers, and applications can be expensive.
Compatibility concerns – IPv4‑only devices cannot talk directly to IPv6‑only devices without translation layers like NAT64 or 464XLAT.
No financial incentive – Many organizations see no immediate revenue benefit from IPv6 deployment.
Real-World Examples from ISPs and Cloud Companies
Mobile Carriers
Indian mobile carrier Reliance Jio deployed an “IPv6‑only” mobile network strategy, which is why India now has some of the highest IPv6 adoption rates in the world. India is actively solving running out of IPv4 addresses by skipping IPv4 where possible.
Residential ISPs
Many operators rely heavily on CGNAT as a stopgap, especially for low‑usage subscribers. A single public IPv4 address can serve over 100 customers simultaneously. Millions of home internet users have never owned a unique public IPv4 address. They have always lived behind one or more layers of NAT, sharing addresses with thousands of strangers. This is the everyday reality of running out of IPv4 addresses.
AWS and Cloud Provider Pricing
Since February 2024, AWS has charged 0.005 per hour for every public IPv4 address. That applies whether the address attaches to an instance, a load balancer, a NAT gateway, or sits idle. The cost works out to roughly 3.65 per IP per month. At scale, these costs add up fast.
| Number of Public IPs | Monthly Cost | Annual Cost |
|---|---|---|
| 100 IPs | $365 | $4,380 |
| 1,000 IPs | $3,650 | $43,800 |
| 5,000 IPs | $18,250 | $219,000 |
Cloud providers are monetizing running out of IPv4 addresses directly.
Simple Analogies for Beginners
Here are three analogies to make running out of IPv4 addresses easier to grasp.
Apartment Building Parking Spaces
Imagine the IPv4 address space is a massive apartment building with 4.3 billion parking spaces. For years, new apartments kept being built, each taking parking spaces. In 2011, the last unassigned parking space was claimed. Now, the only way to get a parking space is to buy or rent one from an existing tenant.
Post Office with Limited Lockers
Think of a post office with exactly 4.3 billion mail lockers. Every person or device that wants mail delivery needs their own locker. NAT is like a shared mailbox that serves an entire apartment building – a single locker that still manages to sort mail for every unit inside.
Seats on Earth
Imagine you need to assign each person on Earth a unique seat number, but you only have 4.3 billion seats. That is fewer than one seat per person – and we have nearly 8 billion humans. We would need every person to share a seat with at least one other person. Running out of IPv4 addresses forces exactly that kind of sharing.
Frequently Asked Questions (FAQ)
Q: Will the internet stop working because of running out of IPv4 addresses?
No. The internet runs on allocated IPv4 addresses, not the free pool. The shortage means no new free addresses, but existing addresses continue working.
Q: How can I check if I am behind CGNAT?
Compare your router’s WAN IP address with your public IP. If they differ, and the WAN IP falls into a private range (such as 100.64.0.0/10), you are behind CGNAT.
Q: Can I buy my own IPv4 address?
Yes. You can purchase IPv4 addresses on the secondary market through approved brokers. You must also demonstrate justified need to the relevant regional internet registry.
Q: What is 464XLAT?
464XLAT is a translation technology that allows IPv6‑only devices (like some modern smartphones) to reach IPv4‑only services on the public internet.
Q: How does IPv6 improve security over IPv4?
IPv6 mandates IPsec support for encryption and authentication between peers. Additionally, IPv6 makes NAT unnecessary, which reduces the attack surface of NAT traversal. IPv6 also supports privacy extensions (temporary, randomized addresses) that make device tracking harder.
Q: Why does China have such low IPv6 adoption?
China has IPv6 adoption of only about 5%, primarily due to its large population still using older IPv4 infrastructure and a slower national transition strategy compared to countries like India.
Q: How does the CISA GitHub data leak relate to IPv4?
The CISA GitHub data leak exposed plaintext credentials, including passwords and access tokens, in a public repository. While that leak did not directly cause running out of IPv4 addresses, it highlighted how poor credential management can compromise the systems that manage IP addresses, cloud infrastructure, and network devices. For the full story and lessons on securing your credentials, see our detailed coverage of the CISA GitHub data leak.
Charts and Graphics Ideas
| Chart Type | What It Shows |
|---|---|
| Line graph | Global IPv4 consumption over time (1981–2026) |
| Pie chart | Allocation of the 4.3 billion IPv4 addresses |
| Timeline bar chart | Exhaustion dates for IANA and each RIR |
| Bar chart | IPv6 adoption rates by country |
| Table | IPv4 vs. IPv6 feature comparison |
| Donut chart | Global internet traffic: IPv6 vs. IPv4 |
| Map | Which RIR covers which region |
| Price trend chart | IPv4 address prices over time (5 in 2011 to 50+ in 2026) |
What Comes Next?
The Hybrid Internet
IPv4 will not fully disappear for decades, if ever. Too many legacy systems, appliances, embedded devices, and network configurations depend on IPv4. The two protocols will coexist through dual‑stack configurations – devices that speak both IPv4 and IPv6 – and translation technologies. Running out of IPv4 addresses does not mean IPv4 is dead.
The Role of Economics
As IPv4 addresses become more expensive ($50+ per IP) and IPv6 adoption crosses 50% globally, the economic incentive to finally complete the transition grows. Cloud providers charge for IPv4 addresses, and BYOIP (Bring Your Own IP) programs allow customers to use their own purchased IPv4 blocks in the cloud, avoiding those fees.
The AFRINIC Situation
AFRINIC, the African internet registry, remains the only RIR with remaining IPv4 address space. This has made it a target for misuse, with fraudsters attempting to improperly acquire and resell these last available free IPv4 addresses.
The Final Transition
IPv6 adoption will accelerate as private IPv4 space depletes and more cloud providers introduce pricing models that favor IPv6.
Summary
Running out of IPv4 addresses is not a future problem. It is today’s reality. The 4.3 billion addresses that once seemed infinite have been fully allocated. Every new connected device must now share a public IPv4 address through NAT, CGNAT, or increasingly through IPv6.
IANA exhausted its central pool in 2011. Five RIRs have since exhausted their free pools, with RIPE NCC expecting exhaustion by late 2026. IPv4 addresses are now a scarce, valuable commodity traded on a billion‑dollar secondary market. NAT and CGNAT have delayed the impact but created security issues of their own.
IPv6 is the long‑term solution. Global IPv6 adoption crossed 50% in March 2026. Yet the transition remains uneven and slow in many regions. The internet will run on both protocols in parallel for the foreseeable future. Meanwhile, the shortage will continue to drive up prices and create new security challenges until the transition is complete.
