Introduction to IPv6

As a future network engineer, you must understand IPv6, not just because it is another type of IP address, but because IPv6 is designed to replace IPv4 and ensure the Internet can keep growing.

The rapid increase in the number of connected devices around the world has made it clear that IPv4 alone is no longer sufficient to support this growth.
Back in 1990, only about 3 million devices were online. Today, with the rise of smartphones, cloud services, and the Internet of Things (IoT), there are now over 75 billion connected devices, far surpassing the limits of IPv4.

Figure 1 – Devices quickly surpass IPv4’s 4.3B address limit

IPv4 addresses are based on 32 bits, which allows for a maximum of about 4.3 billion unique addresses. At first, that seemed enormous in the 1980s and 1990s.

But as the Internet expanded, the number of devices needing addresses grew far beyond that limit. By 2010, the number of connected devices worldwide was already more than three times higher than the total number of available IPv4 addresses.

IPv6 was created to permanently resolve the address shortage while also introducing important improvements over IPv4.

Before diving deeper into IPv6, let’s review how IPv4 addresses were allocated and why they eventually ran out.

In the early 1980s, the IANA (Internet Assigned Numbers Authority) was directly responsible for distributing IPv4 addresses to universities, companies, and government institutions. At that time, the Internet was still small, so this centralised system worked well.

By the early 1990s, however, the Internet had grown massively. A more efficient and fair method was needed, which led to the creation of the Regional Internet Registries (RIRs).

The Rise of RIRs

The establishment of RIRs decentralized the process, dividing responsibility across different parts of the world:

• APNIC – Asia-Pacific

• RIPE NCC – Europe, Middle East, Central Asia

• ARIN – North America

• LACNIC – Latin America, Caribbean

• AFRINIC – Africa

Figure 2 – IPv4 address allocation hierarchy

Here’s how the system worked:

1. The IANA maintained control of the global IPv4 pool.

2. Large blocks of addresses were allocated to the RIRs.

3. Each RIR distributed smaller blocks to ISPs and large organizations.

4. ISPs then assigned addresses to companies and end users.

This structure made allocation more organized and sustainable for a while. But as Internet growth continued, engineers had to develop new techniques to stretch the limited IPv4 space.

Techniques to Stretch IPv4

Originally, IPv4 used classful addressing (Classes A, B, and C). While simple, this system was inefficient, many addresses were wasted.

To improve efficiency, several solutions were introduced:

Figure 3 - Timeline to IPv6 Standard

• In 1993, CIDR (Classless Inter-Domain Routing) and VLSM (Variable Length Subnet Masking)
  → Allowed more flexible subnetting and reduced waste.

• In 1994, NAT (Network Address Translation) with private addresses
  → Enabled many devices in a private network to share a single public IPv4 address, greatly slowing down the rate of consumption.

These methods helped extend the life of IPv4, but they only delayed the inevitable.