Title: Learn IPv6 Address Presentation
Course: CIS 208: Linux/UNIX III: Intermediate System Administration, Networking, and Security ~ For IGNITE Review > Section: Learning Modules

Learn IPv6 Address Presentation

An IPv6 address is represented as eight groups of four hexadecimal digits, each group representing 16 bits (two octets). The groups are separated by colons (:). An example of an IPv6 address is:

- 2001:0db8:85a3:0000:0000:8a2e:0370:7334

The hexadecimal digits are case-insensitive, but IETF recommendations suggest the use of lower case letters. The full representation of eight 4-digit groups may be simplified by several techniques, eliminating parts of the representation.

Source: By Ipv6_address.svg: Indeterminate derivative work: BobbyPeru (Ipv6_address.svg) [Public domain], via Wikimedia Commons

Leading zeroes

Leading zeroes in a group may be omitted. Thus, the example address may be written as:

- 2001:db8:85a3:0:0:8a2e:370:7334

Groups of zeroes

One or more consecutive groups of zero value may be replaced with a single empty group using two consecutive colons (::). Thus, the example address can be further simplified:

- 2001:db8:85a3::8a2e:370:7334

The localhost (loopback) address, 0:0:0:0:0:0:0:1, and the IPv6 unspecified address, 0:0:0:0:0:0:0:0, are reduced to ::1 and ::, respectively. This two-colon replacement may only be applied once in an address, because multiple occurrences would create an ambiguous representation.