IPv6 Address: Types, Structure & Purpose

Instructor: Vignesh Sivabalan

Viignesh has an MS in information technology.

This lesson introduces you to Internet Protocol version 6 (IPv6) address, explaining its types (modes), structure and purpose. IPv6 is the best alternative for its predecessor, IPv4.

An Introduction to IPv6

The IPv6 (Internet Protocol version 6) is a 128-bits address format, it is an upgrade to an earlier 32-bits IPv4 addressing format used in our network. IPv6 simplifies network and host configuration and also corrects few drawbacks of IPv4 (Internet Protocol version 4). In IPv6, eight 16-bits blocks make up to the entire 128 bits. Below is a binary format the 128-bits IPv6 address also spliting the group of eight 16-bits:

001000000000001 1111111011111011 0011001000111000 0000000000000000 1101111111100001 0000000000000000 0000000001100011 0000000000000000

One can convert a binary format like above to hexadecimal format separated by a (:) colon. Example -


To understand the structure of the IPv6 address format, we must first look into the Hexadecimal numbering system. Hexadecimal numbers use base (radix) value of 16. A hexadecimal number starts from 0 to 9 and then after 9 its from A to F representing numbers from 10 to 15.

Decimal Number Binary Value Hexadecimal Value
0 0000 0
1 0001 1
2 0010 2
3 0011 3
4 0100 4
5 0101 5
6 0110 6
7 0111 7
8 1000 8
9 1001 9
10 1010 A
11 1011 B
12 1100 C
13 1101 D
14 1110 E
15 1111 F

Need for IPv6 Address

IPv4 has a 32-bit format and can generate maximum 4.3 billion unique IP addresses. The IPv4 addressing seems quite large, but it cannot sustain the demand from the rapidly increasing number of network devices connected to the internet. There are few technologies like Network Address Translation that helps in extending the IPv4, but this system would soon get exhausted. Thus, the growing demand for an IP addressing format that can generate large volumes of unique IP addresses is inevitable, which lead to the evolution of IPv6. With its 128-bits address format, IPv6 can handle up to 3.4 x 10^38 (to the power 38) unique IP addresses.

Three Types of IPv6 Addressing Modes

In networking, the addressing modes denote the technique of hosting an IP address on a computer network. Internet Protocol version 6 (IPv6) provides three kinds of methods for addressing a single device (and host system like a Laptop, Desktop, PDA, Tablet). Let us take a walk through the three IPv6 addressing modes in detail.

1. Unicast Mode

In the Unicast mode of addressing, the particular host on the network is identified uniquely using its IPv6 address. It is a one source to one destination communication. The IPv6 packet contains the message, along with the source and the destination IP addresses. And by using the unique destination IPv6 address, the message is routed to the target device on the network.


Let's imagine that you are sending a text message to your friend from your mobile. The text message service will use the cellular phone network. So the source ID is your mobile number, and the destination ID is your friend's mobile number. In this context, your personal mobile number is something similar to the unique 128-bits IPv6 address for network devices. The source and the destination use their unique 128-bit IPv6 address to communicate with each other over the network.

Figure 1: Unicast Address Mode

2. Multicast Mode

In multicast mode, a single host sends messages to multiple hosts over the network, and this communication takes place using special kind of IPv6 address called Multicast address. The destination hosts that are interested to receive the multicast message should first add themselves in that multicast group. All the hosts that join the multicast group receive the multicast information, in form of packets. This can be visualized as one to many communication protocols.


Imagine that you are creating a message group of your local friends in your contact list on a Messaging App. You will not be using the entire contacts list but would rather select a few from your contacts. Those who are willing to join the group will need your permission. You are the group admin who sends messages so that all your friends in that group can read it.

Figure 2: Multicast Address Mode

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