IPv6 Overview

Why IPv6 ?

Two good reasons to move to IPv6 are as follows:
• IPv6 has more address space available.
• We are running out of public IPv4 addresses.

With IPv6, upper-layer applications still work like you are used to with IPv4.

The biggest change is that we are doing a forklift upgrade to Layer 3 of the OSI model.

Address Format

Length:           IPv6 addresses are 128 bits long.

Groupings:    IPv6 addresses are segmented into eight groups of four hex characters.

Separation of groups:   Each group is separated by a colon (:).

Length of mask:    Usually 50 percent (64 bits long) for network ID, which leaves 50 percent (also 64 bits) for interface ID (using a 64-bit mask).

Number of networks:   The network part is allocated by Internet registries 2^64 (1.8 x 10 19 ). This allows room for billions of networks.

Example Address :


We can abbreviate the address.

  • remove the leading 0s. A quartet of 0000 will leave a single 0.
  • Replace that set of quartets with double colon ( :: )
  • :: can be used once in a single address



IPv6 Address Types Brief Overview and Their First Hex Digit(s)

Global Unicast > 2 0r 3 (originally); all not otherwise reserved (today)
Unique Local > FD
Multicast > FF
Link-Local > FE80

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