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In this final installment of the don’t panic series “Introducing IPv6,” you will learn about Neighbor Discovery and Stateless Address AutoConfiguration.

The beauty of the IPv6 header is that it has been streamlined and contains only those pieces of information that are necessary on every IPv6 packet. All optional IP information is encoded in extension headers, which are added to packets between the standard IPv6 header and the upper-layer header.

As with IPv4, an IPv6 address serves as an identifier for an interface or group of interfaces. Also like IPv4, IPv6 addresses come in several types, based on how they represent those interfaces. IPv6 has three types of addresses. This post covers all three, plus some special purpose addresses as well.

The primary difference between IPv4 and IPv6 addresses is length. IPv4 addresses are 32 bits long and IPv6 addresses are 128 bits long. This means that an IPv4 address is made up of 32 1s and 0s while an IPv6 address is made up of 128 of them – 128 binary digits. This massive length forces IPv6 addresses to be written using a different notation than IPv4 addresses and thus makes them very easy to distinguish from IPv4 addresses.