IPv6 fundamentals

What is IPv6, and how does it work?

IPv6 is the newer version of the Internet Protocol: the system that lets devices address one another and move traffic across networks. It was introduced because IPv4 ran out of room long before the internet stopped growing.

Address growth

IPv4 did not have enough room left

An IPv4 address is 32 bits long. In theory that gives just over 4.29 billion addresses. It sounded enormous when IPv4 was designed, but it is a tight fit for today's phones, laptops, home routers, cloud platforms, cameras, and industrial equipment.

IPv6 uses 128 bits instead. The extra space lets providers allocate networks more cleanly and reduces the pressure to share one public address between many customers. It does not create a separate internet; it is the modern protocol used to reach the same services and networks.

128 bits

Addresses are longer, not harder

An IPv6 address has 128 bits. On screen, that usually appears as eight groups of hexadecimal digits separated by colons: 2001:0db8:0000:0000:0000:0000:0000:0001.

Most of that is not typed out in day-to-day work. Leading zeroes may be left out, and one run of zero groups may become ::. So the same address is normally written as 2001:db8::1.

Address types

The beginning of an address matters

Some addresses can be routed across the public internet. Others work only on the local link, inside a private network, or for a multicast group. ::1, for example, is the IPv6 loopback address: it always points back to the same machine.

That is why an address lookup needs context. An IP address can describe a network allocation or provider, but it is not a reliable way to identify a person or a precise physical address.

Transition period

The switch happens gradually

There is no worldwide cut-over date. Many networks run IPv4 and IPv6 side by side, a setup known as dual stack. A device uses whichever protocol is available for the connection. Translation gateways and proxies fill the gaps where one side only speaks IPv4 or IPv6.

You may also see an IPv4 address written in an IPv6-aware application as an IPv4-mapped address. That is a convenient software notation, not proof that the remote host has native IPv6 connectivity.