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> Chapter 15 - IPv6 > Introduction


The origins of Internet Protocol Version 6 (IPv6) date back to December 1998 with the publication of RFC 2460, which describes IPv6 as the successor to IPv4, the standard communications protocol still in use by the majority of users today. This transition away from IPv4 was a direct response to the foreseeable exhaustion of 32-bit IPv4 addresses, which are virtually all but assigned—all 4.3 billion.

IPv4 uses 32-bit addresses, which means that there is a theoretical address limit of 2 to the power of 32. The IPv6 address scheme is based on a 128-bit address, resulting in a theoretical address limit of 2 to the power of 128.

Possible addresses:

IPv4 = Roughly 4.3 billion

IPv6 = Over 340 undecillion (340 followed by 36 digits)

Assuming a world population of approximately 8 billion people, IPv6 would allow for each individual to have approximately 42,535,295,865,117,200,000,
000,000,000 devices with an IP address. That’s 42 quintillion devices, so it’s unlikely that we will ever need to worry about the availability of IPv6 addresses.

Aside from the difference of possible addresses, there is also the different formatting of the addresses. A computer would view an IPv4 address as a 32-bit string of binary digits made up of 1s and 0s, broken up into 4 octets of 8 digits separated by a period:



To make the number more user-friendly, we translate the address into decimal, again 4 octets separated by a period:


A computer would view an IPv6 address as a 128-bit string of binary digits made up of 1s and 0s, broken up into 8 octets of 16 digits separated by a colon:



To make this number a little more user-friendly, we translate it into hexadecimal, again 8 octets separated by a colon, for example:



We can further simplify the above address. Because any four-digit group of zeros within an IPv6 address may be reduced to a single zero or altogether omitted, the above address can be reduced to: