IPv4: The Legacy Internet Protocol That Will Outlive Most of Us

February 25, 2025 by , in Blog Linux

IPv4 has been the backbone of the internet since its inception and despite its well-known limitations it will not be fully deprecated in our lifetime. IPv6 adoption is growing, but IPv4 is deep in the global networking infrastructure, so its full phase out is a long way off.

Much like the Agent Smith clones in The Matrix, IPv4 just won’t go away. Even with IPv6 on the horizon as the next gen standard, IPv4 lingers everywhere—plugged into routers, devices and entire networks. This article will explain how IPv4 became the dominant protocol, the workarounds that keep it alive, and why its final chapter is still far off.

The History of IPv4


Source: Google IPv6 Adoption Statistics.

Late 1960s – 1970s: The Foundation of the Internet

1980s: IPv4 is Born

  • 1980: The first formal standard version of IP was created as IPv4, defined in RFC 760.
  • 1981: IPv4 was refined in IETF RFC 791, replacing earlier definitions.
  • 1982: The US Department of Defense mandated TCP/IP as the standard for military networking.
  • 1983: The Domain Name System (DNS) was created to simplify internet navigation.
  • 1984: RFC 920 defined the first top-level domains (.com, .gov, .edu, etc.).
  • 1988: Jon Postel established the Internet Assigned Numbers Authority (IANA).
  • 1989: Sir Tim Berners-Lee invented the World Wide Web, setting standards for URLs, HTTP, and HTML.

1990s: Scaling the Internet

2000s: The IPv4 Shortage Begins

2010s: IPv4 Exhaustion and Market Formation

  • 2011: IANA exhausted the global IPv4 address pool; APNIC was the first RIR to deplete its IPv4 addresses.
  • 2011: The first commercial IPv4 transfer took place between Nortel and Microsoft.
  • 2012: RIPE NCC exhausted its IPv4 addresses.
  • 2014: LACNIC announced IPv4 exhaustion.
  • 2015: ARIN depleted its free IPv4 address pool.
  • 2017: IPv4 market prices surged as address transfers became common.

2020s: IPv4 remains dominant.

The Legacy of IPv4

IPv4 was never designed to support the scale of the modern internet. With only about 4.3 billion unique addresses, exhaustion was an issue as early as the 1990s and workarounds like NAT (Network Address Translation) and later IPv6 were developed. But these stop gap measures have been so effective that they have prolonged IPv4’s life indefinitely.

Many organizations, from enterprises to ISPs, still rely heavily on IPv4. The cost of transitioning to IPv6 is a big deterrent, and the lack of a forced deprecation timeline has only reinforced the status quo. While big tech companies like Google, Facebook, Cloudflare, and Amazon have adopted IPv6, much of the internet still runs on legacy IPv4 infrastructure.

IPv4 Addresses Are Now a Commodity

Skyrocketing prices in the IPv4 secondary market underscore ongoing demand. Because all globally available IPv4 addresses are already allocated, anyone requiring more must purchase them from existing holders. As a result, blocks of IPv4 addresses can cost tens of thousands of dollars—or more—depending on size and scarcity.

This highlights that IPv4 still holds significant monetary value, even as IPv6 adoption continues to rise.

The Stubborn Survival of IPv4

Like Agent Smith clones from The Matrix, IPv4 shows continued persistence and refuses to die.
Like Agent Smith clones (The Matrix) — IPv4 refuses to die.

Decades after the introduction of IPv6, a significant portion of the internet still relies on IPv4, and there is no definitive timeline for its deprecation. The reasons for IPv4’s persistence are multifaceted, combining technical, economic, and logistical challenges. Here are the key reasons why IPv4 won’t be deprecated anytime soon:

  • Massive Installed Base: Billions of devices from routers to IoT sensors are hardcoded for IPv4 and will take decades to replace.
  • No Official Deprecation Date: Unlike other protocols that are forcibly retired, IPv4 has no mandatory sunset timeline.
  • Economic Factors: Upgrading networks to IPv6 requires investment, and many see little immediate return.
  • Global Disparities in Adoption: Some regions are way ahead in IPv6 deployment, while others are almost entirely on IPv4.
  • Workarounds Are Too Effective: NAT, CGNAT, IPv6-to-IPv4 tunneling and Dual-stack configs keep IPv4 alive. (see below)

Workarounds Extending IPv4’s Lifespan

ISPs, networking companies, and users have found ways to stretch IPv4 way beyond its original design. These workarounds allow them to function within its constraints. While these solutions keep IPv4 relevant, they also introduce complexity, performance trade-offs and long-term sustainability issues. Collectively, despite address exhaustion, the following workarounds for extending IPv4 help to remove the pressure to adopt IPv6:

NAT in IPv4

Network Address Translation (NAT) underpins most household internet connections. It works by taking requests from multiple devices in your home and sending them through a single public IPv4 address. This address rewriting helps stretch the limited IPv4 space, so each device can go online without needing a unique external IP.

On the other hand, in an IPv6 setup, ISPs typically assign a block of addresses—often a /56 or /60 prefix—that can be subdivided into multiple /64 subnets. Each /64 has more than enough addresses for all your home’s devices, making NAT unnecessary. Every device can receive its own globally routable IPv6 address, while home routers provide a firewall to protect against unwanted inbound traffic.

CGNAT (Carrier-Grade NAT)

Internet service providers deploy CGNAT on a large scale. So all the subscribers in a community are behind a smaller pool of public IPv4 addresses. While CGNAT is efficient, it adds complexity and potential performance bottlenecks.

IPv6-to-IPv4 Tunneling

These tunneling methods transport IPv4 traffic over IPv6 networks (or vice versa) and act as a bridge when native IPv6 is not supported everywhere. Tunnels allow ISPs to keep service for legacy IPv4 applications and thus delay the transition to full IPv6 adoption.

Dual-stack configurations

Running both IPv4 and IPv6 is the norm for many ISPs, allowing IPv4 to persist even as IPv6 grows. With dual-stack, a device or network is assigned both IPv4 and IPv6 addresses. This means older devices using IPv4 can still connect, while newer systems can use IPv6. However, rapid IPv6 adoption by mobile carriers and ISPs in regions like India shows how subscriber growth and limited IPv4 space can push entire networks to prioritize IPv6.

Rapid IPv6 adoption in India.
Source: Google IPv6 Adoption Statistics (India).

The Slow March to IPv6

Despite being available for over 25 years, the IPv6 adoption rate has not really increased in the past few years. According to Google, Facebook and other IPv6 adoption stats (listed below), global adoption is somewhere around 40-45% and fluctuates based on region and service provider. Countries like India, Germany, and the US are leading in IPv6 adoption, but adoption rates vary very widely across the world. Despite this progress, IPv6 is still secondary to IPv4 in many parts of the world.

IPv6 adoption continues to advance at a measured pace, but also unevenly across the globe. Many service providers and cloud vendors now offer IPv6 by default, and some governments encourage adoption through policy or incentives. Certain mobile carriers are leading the way by rolling out IPv6 to new customers because buying or reallocating IPv4 addresses is expensive and painful.

Although newer devices and software come with robust IPv6 support, the economic and logistical barriers to IPv4 will keep it in use for decades to come. Countries that invested in modernizing their broadband infrastructure tend to see higher percentages of IPv6 traffic. Meanwhile, older networks and smaller ISPs stick to IPv4 and still rely on NAT or CGNAT to keep IPv4 alive.

Looking forward, widespread adoption of the Internet of Things (IoT) may be the catalyst for deeper IPv6 penetration. Each new sensor or smart device needs an address, and IPv6 has an almost endless supply. Over time, as outdated hardware is replaced and more services require IPv6 only connectivity, the percentage of IPv6 traffic will rise – but only gradually. Unless there’s a forced transition or a sudden global push, IPv4’s massive installed base means it will coexist with IPv6 for decades to come.

Additional IPv6 Adoption Statistics

The following websites provide ongoing statistics about the adoption of IPv6:

Useful IPv6 Tools and Resources

Linux IPv6 Resources

Conclusion

IPv6 adoption has doubled since 2018, but IPv4 won’t be going away anytime soon. The vast amount of legacy infrastructure, IoT devices, embedded systems with continue the use of IPv4, NAT and CGNAT and the widespread use of dual-stack networks to keep IPv4 going for decades. Some industries and regions are moving faster to adopt IPv6, but others are lagging behind.

Without a deprecation date, IPv4 will become a legacy protocol—not dominant, but still present in niche areas, much like COBOL in banking. IPv6 will eventually take over, but realistically, IPv4 won’t be fully phased out until long after most of us reading this have moved on.

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