A Brief History of IPv6 and Where Adoption Is Already Taking Off
The transition to IPv6 has been “coming soon” for more than a decade. Some people decided it was time to say goodbye to IPv4 back in May 2014, when IANA sold their final remaining blocks of IPv4 addresses. While IPv6 adoption has not taken off as rapidly as many observers predicted, we are now starting to see the transition gather steam.
At SixMap, one of our core technologies gives customers the ability to continuously discover, assess, and monitor assets in both the IPv4 and IPv6 address spaces. While IPv4 usage is still most common among our customer base, IPv6 implementation is a growing segment and we’ve found many organizations are still underprepared for the transition to IPv6.
To help security teams get ready for the transition to IPv6, we’re publishing a three-part series on The Switch To Six. In this post, Part I, we’ll cover a brief history of IPv4, an introduction to IPv6, cover both the limiters and drivers of adoption, and explain why IPv6 usage is already taking off in some regions of the world.
A Brief History of IPv4
The Internet Protocol, Version 4 is a standard that was fully deployed in 1983 and has been running the majority of the internet ever since. First outlined in RFC 760, IPv4 was designed to use 32-bit long addresses to allow remote devices to communicate with one another over a global network. Since a bit is a binary data point– either a 1 or a 0– there are 232 possible IPv4 addresses, or roughly 4.3 Billion unique addresses.
While 4.3 Billion addresses may sound like a lot, it’s not in today’s highly digital world. In fact, all of the IPv4 addresses are spoken for. Not every address is necessarily in use at every moment, but they are all owned and controlled by various entities.
In reality, there are far more internet-connected devices in use today than there are IPv4 addresses. Not every single device needs to have its own dedicated IPv4 address. A network can have one public IP address and then route traffic internally to the appropriate device using a technology called NAT, or Network Address Translation.
To put it simply, NAT allows multiple devices to share a single public IPv4 address. NAT rules are built into not only home networks, but increasingly complex systems all the way up to your ISP, allowing far more than the technical maximum number of IP addresses to be used.
An analogy will help illustrate how NAT works in practice. Imagine a corporate office with a single public telephone number and a human switchboard operator. Inside the company, each employee has an extension number.
Suppose we have a person, Bob, who works in accounting, and he’s extension 123. When Bob wants to make an outgoing call, he dials 9 to get an outside line, and then makes the call through the public company line, with the switchboard knowing that extension 123 is connected to external line (456) 789-0123. But the other end of the call doesn’t know that they’re talking to extension 123. They only know, and only need to know, that they’re being called from the company number.
If that external person tries to call back, they either have to know the extension or the name of the person at the company they’d like to speak with, so the receptionist or switchboard operator can route the call to the right employee.
An Introduction To IPv6
IPv6 is the replacement version for IPv4. There was an experimental version of IPv5 but, due to its inability to solve the known scalability challenges with IPv4, it was never pursued beyond an early initial phase. As a standard, IPv6 was available all the way back in 1998, when it was drafted, due to what then-seemed imminent exhaustion of the IPv4 space.
One of the major differences between IPv4 and IPv6: there is no need for NAT with IPv6. All devices can have a fully unique address, that only they ever use. So rather than Bob having to call out through the company line, everyone at the company has their own dedicated phone line, and all of them are owned by the company.
This is possible due to the sheer scale of IPv6. As noted above, IPv4 uses a 32-bit address space, meaning 232 distinct addresses. That’s roughly one address for every two people in the world now, but was roughly 1-to-1 when IPv4 was rolled out.
By contrast, IPv6 has an 128-bit address space, allowing for 2128 or 340 undecillion unique addresses. Written out in full form, that’s:
- 340,282,366,920,938,463,463,374,607,431,768,211,456 addresses.
There are so many IPv6 addresses that, if we were to calculate the length of the observable universe and convert the measurement to millimeters, we could assign roughly 3.6 Billion IPv6 addresses to each and every millimeter. That’s more than 80% of the number of addresses in the whole IPv4 space, assigned to each and every millimeter across the universe as we know it.
Inhibitors & Drivers Of IPv6 Adoption
Several key factors have played a role in delaying IPv6’s adoption as the IPv4 replacement. First and foremost, the initial distribution of IPv4 addresses was not systematic or allotted evenly between countries. While some regions had a shortage of IPv4 addresses long ago, other regions had a relative abundance of IPv4 blocks. For instance, the Massachusetts Institute of Technology (MIT) received more IPv4 addresses than all of the nation of China.
This uneven distribution had two primary effects.
- First, developed countries had more space to start with so they were more willing to build a large stack of technologies, such as NAT and other networking methods, that implicitly assumed IPv4 would be in place indefinitely. Once a large ecosystem of technologies were built around IPv4, moving onto IPv6 seemed increasingly difficult, complex, and risky.
- Second, developing countries with very limited IPv4 allotments had a difficult choice: they could invest heavily in acquiring and managing scarce IPv4 addresses using complex NAT architectures, or build new infrastructure with IPv6 from the beginning. Even while making use of the few IPv4 addresses they had, it made sense to quickly get ready for the switch to IPv6 due to space constraints and the cost of hardware to support complex NAT systems.
Now, we’re starting to see signs of transition to IPv6 globally, even in regions where IPv4 addresses were most readily available. Cisco reports that IPv6 traffic is beginning to overtake IPv4 traffic globally, “with IPv6 traffic on the Internet now surpassing 50% by all measures.”
So what’s driving global IPv6 adoption now, in Q4 2025? The main cause is that many large network providers– like cloud computing platforms, Internet Service Providers (ISPs), and other tech giants like social media platforms– have started making the move to IPv6 out of necessity. There are simply too many devices to use IPv4 and managing NAT at the scale of, for example, a modern mobile network, would be complex and error-prone. IPv6 is a simpler and more cost effective way to scale.
Regions Where IPv6 Is Already The Norm
This scarcity of IPv4 in some geographies became a forcing function to transition to IPv6. As a result, IPv6 adoption is well above 50% in many countries: “France, Germany, and India are at 78%, 76% and 72%, respectively,” according to Cisco.
Of course, a shortage of IPv4 space isn’t the only reason to make the transition. IPv6 does bring several major advantages, and is growing in importance due to the relatively high costs of acquiring new IPv4 netblocks on secondary markets. Whereas a /16 IPv4 block with 65,535 addresses goes for more than $1 Million, a /48 IPv6 block with more addresses than the entirety of the IPv4 space can be leased for a few hundred dollars per year.
Adopting IPv6 brings both technical and business benefits:
- Cost Savings – Procuring IPv4 addresses on secondary markets has become relatively expensive, while registering huge numbers of IPv6 addresses is very inexpensive.
- Simplicity of Network Operations – Virtually unlimited IP addresses eliminate the need for NAT, simplifying network design and supporting the growth of connected devices.
- Improved Performance – Streamlined packet processing and reduced NAT overhead enhance routing efficiency and lower latency.
- Built-In Security – Native IPsec support enables encrypted, authenticated communication at the network layer by default.
- Simplified Configuration – Stateless address autoconfiguration (SLAAC) reduces manual setup and DHCP reliance.
- Better Mobility Support – Mobile IPv6 allows seamless connections as devices move across networks without session interruptions.
SixMap Simplifies The IPv6 Transition
6Gen, one of SixMap’s core technologies, was designed to discover hosts in the vast IPv6 address space. Using a technique called computational mapping, the 6Gen algorithm discovers where IPv6 hosts are most likely to be found, turning the unimaginably large IPv6 space into a more practical and manageable space to find active assets.
With IPv4, it’s possible to simply check every address in the entire IPv4 space. A basic assessment of all 4.3 billion addresses can be completed in a matter of hours. When it comes to IPv6, this brute force approach simply doesn’t work. The IPv6 space is too large to inspect each and every address so more sophisticated techniques are necessary. That’s where SixMap’s technology comes in.
While 6Gen was originally designed to find IPv6 hosts, the computational mapping techniques used can also be applied to efficiently discovering and assessing hosts in the IPv4 space. This minimizes the amount of data being sent over the network while improving the completeness of host discovery and increasing the fidelity of service exposure and risk findings.
So what does this all mean for customers? In short, it means much better visibility across IPv4 and IPv6. After mapping out your organization, SixMap continuously finds all of the network assets– netblocks, IP addresses, and domains– that you need to defend. Each asset is inspected in a comprehensive exposure assessment. Vulnerabilities and misconfigurations are detected and prioritized using threat intelligence data.
Reach out to the SixMap team to get a better understanding of how we can help you discover, assess, and monitor your network assets across IPv4 and IPv6.
