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What is IPv6 (Internet Protocol version 6)?

Author : Saraswati
Last Modified: March 13, 2024 
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IP stands for Internet Protocol, basically your digital identity over the internet. Every device connected to the internet is located with the help of IP addresses to make communication possible. So, you must be wondering what is IPv6.

The first version of IP is IPv4 which had some drawbacks therefore IPv6 was introduced to the market. After which, IPv6 is in demand since 2006. The most recent version of the Internet Protocol (IP), which directs traffic across the Internet and serves as an identity and location system for machines on networks, is called Internet Protocol version 6.

It closely follows the architectural ideas created in the earlier version of the protocol, Internet Protocol Version 4 (IPv4), and offers end-to-end datagram transfer over various IP networks. The Internet Engineering Task Force (IETF) created IPv6 with the intention of replacing IPv4 in order to address the long-anticipated issue of IPv4 address exhaustion.

What is IPv6?

IPv6 is the latest Internet Protocol version, a network layer protocol that allows communication over the network. It was developed in 1998 by IETF (Internet Engineering Task Force) to overcome the problems IPv4 had. The IPv6 uses 128-bit addressing with an address space of 2^128, which was much bigger than what its predecessor, IPv4, was offering.

Each internet-connected device has a distinct IP address that is used to locate and identify it. The IP addresses that Internet Protocol version 4 (IPv4) used to connect devices at the time of the digital revolution in the 1990s quickly became insufficient to satisfy demand.

In order to address this, the IETF began working on the next-generation internet protocol. In December 1998, IPv6 was designated as a draught standard for the IETF, and on July 14, 2017, it was accepted as an internet standard for widespread deployment.

IPv6 vs IPv4

An IPv4 address comprises four set numbers, and each of these sets of numbers is separated by a single dot(.). All of these separate sets consist of digits from 1 to 3. These four number ranges from 0 to 255.

Here is one example of it –

This collection of distinct numbers is what gives you and everyone else on the entire globe the addresses that allow you to transmit and retrieve data across our Internet connections. The 32-bit address method used by IPv4 allows for the storage of more than 4 billion addresses. It currently handles 94% of all Internet traffic and is regarded as the main Internet Protocol.

At first, it was believed that there would always be enough addresses, however the present scenario opens up a new path for IPv6. Do you know why? There are eight groups of four hexadecimal digits in an IPv6 address. A sample IPv6 address is provided below:


This is the new version of the IP address which was being developed to fulfill the demands of more Internet addresses. It was capable and designed to resolve all the issues which were associated with IPv4.  It permits 340 undecillion unique address spaces with 128-bit address space. It is also known as Internet Protocol next generation (IPbg).

How IPv6 Works?

The working of IPv6 depends on the following key concepts:

1. IPv6 addresses

An IPv6 address has 128 bits, which means four times more than IPv4 (which only has 32 bits). IPv6 addresses are formatted by hexadecimal, not dotted decimal (IPv4). An IPversion6 address consists of 32 hexadecimal numbers, whereas hexadecimal numbers allow 4 bits. These numbers are combined into eight groups of 4 and written using a colon (:) as the separator.

Example: group6:, group7:, group8:, etc.

An IPV6 address is condensed through several techniques due to its length. For example –

2001:0db8:0000:0000:0000:7a6e:0680:9668 can be compressed into 2001:db8::7a6e:680:9668. The main technique deployed is to remove leading zeros. Additionally, consecutive sections of zeros can be moved with two colons (::), even if you enable this approach only once per address to avoid making the address indeterminate or ambiguous.

2. Network and node addresses

In IPv4 addresses, classes allow an address to be divided into two components, A network component and a node component, which are then transferred with subnet masking. Similarly, in IPv6, an address is classified into two 64-bit parts sand: the first 64-bit is the network component (allows routing), and the last 64-bit component is the node component (allows to check the address of the interface or nodes).

3. IPv6 address types and scope

There are three types of IPv6 addresses:

Global Unicast: These addresses start with “2001:” like the prefix group and can be routable over the Internet. These addresses are like IPv4 public addresses.

Link local addresses: It is one of two internal address types that are not routed to the Internet. These addresses allowed inside the internal network are self-assigned and start with “fe80:” like the prefix group.

Unique Local Address: This is a type of internal address that is not on the Internet. These addresses are similar to the IPv4 addresses,, and

4. Using IPv6 addresses in the same resource locator (URL)

A user can receive a network resource such as a web page with HTTP://192.168.121/webpage that opens a new window through an IPv4 network. With Internet Protocol version 6, web pages can also receive format changes. A colon is used as a separator and must be enclosed in square brackets in an IPv6 address.

For example, HTTP://[2001:db8:4531:674::100e]/webpage.

5. IPv6 Loopback

The loopback address shows an interface similar to that of a computer. The TCP/IP protocol stack loops packets back to the same interface in both. In IPv4, is denoted for the network loopback address, and for IPv6, the loopback address is 0000:0000:0000:0000:0000:0000:0000:0001/128. It can be explained by ::1/128 In both IP versions, routers will not forward packets that contain an undefined address. IPv6 unspecified address::/0.

IPv6 Types

There are three types of IPv6, which are as follows:


A unicast address is used to refer to a single host. It is meant to send data to a single destination.


A multicast address can deliver a packet to a group of destination. A multicast address will deliver any packer sent to it to all hosts that are in that particular group.


This address is similar to a multicast address. These IP addresses are usually assigned on routers and servers, and we can assign the same IP on multiple servers. Assigning a unicast address to more than one interface makes a unicast address on anycast address. The closest interface gets the delivery of the packet sent to an anycast address.

Features of IPv6

Here are the top features of IPv6:

  1. An IPv6 is made of 128 bits, divided into eight 16 bits segments or blocks.
  1. Larger address space (2^128) This is how we find out the total number of addresses in it.
  1. Simplified Header
  • The header of IPv4 is 20 bytes and 13 fields.
  • But in IPv6, the header is 40 bytes, but the fields are only 8. (Less complexity as compared to IPv4)
  • The increase in size in bytes of IP versions 6 is because the IPv6 address is total 128 bits, and IPv4 is of 32 bits only.
what is ipv6
  1. End to End Connectivity (No need for NAT) > Every host can directly reach other hosts.
  1. Auto configuration – it supports both stateful and stateless auto-configuration.
  • Stateful here means the host is taking IP from the DHCP server (Like Dynamic mode in IPv4).
  • Stateless here refers to the manual configuration of IP to host (Like static mode in IPv4).
  1. Fast-forwarding/Routing – all important information is in starting of the header. Therefore, the router takes a quick decision, i.e. (The router can verify the important information in the header so it can make fast decision to forward the data).
  1. IPsec (Internet Protocol Security) Data will transfer in encrypted form.
  1. No broadcast.
  1. Anycast supported.
  1. Mobility (in earlier times or today, when we switch to another location, the host’s IP address also changes because of shortage in IPv4, but it does not change IP. Your IP will remain constant weather you switch your location or not).
  1. Smooth Transition
  • It isn’t backwards-compatible, therefore a complete change may not be feasible to IPv4 towards IPv6.
  • To get around this issue there are a number of technologies that can be employed to make sure that there is a smooth and seamless change between IPv4 into IP version 6.
  • It includes three technologies: Dual-Stack, Header Translation, Tunnelling

IPv6 Address Format

IPv6 addresses are formatted by 128 bits and organized into eight groups, each group containing 16 bits. Each group was represented as four hexadecimal digits and a colon separated the groups.

Below is an example of a full IPv6 address:


An IPv6 address is divided into two parts, which are a network component (the first 64 bits of the address allow routing) and a node component (the last 64 bits allow checking the address of the interface). It is derived from the physical or MAC address through the 64-bit Extended Unique Identifier (EUI-64) format published by the Institute of Electrical and Electronics Engineers (IEEE).

Network nodes can be divided into blocks of 48 bits and blocks of 16 bits. The upper 48-bit field allows global network addresses, while the lower 16-bit allows subnets on internal networks and is controlled by network managers. Additionally, example addresses can be shortened because the addressing scheme enables the removal of any leading zeros with any sequence, including only zeros.

The compressed version is shown below:


The specific layout of an IPv6 address varies depending on its format. There are three basic parts that make up an address:

  • Routing prefix
  • The subnet ID
  • The interface ID
Image showing IPv6 Address Message format divided between routing prefix, sybnet ID, and Interface ID.

Routing prefix and Subnet ID, both show two main levels in which the address is created, i.e. either global or site-specific. The routing prefix is the number of bits that can be divided, usually based on the decision of Internet registries and Internet service providers (ISPs).

If you see an IPv6 address, the leftmost set of numbers, i.e., the first 48 bits, is known as the site prefix. The Subnet ID is the next 16 bits that determine the site topology. The latter 64 bits are known as the interface ID, which can be configured automatically or manually.

Advantages of IPv6

Here are some advantages of Internet Protocol version 6 –

  • Reliability increases of the network
  • Faster Speeds: Multicast is supported by it as opposed to broadcast in IPv4.This function enables simultaneous transmission of packet flows with high bandwidth requirements, such as multimedia streams.
  • Greater Security: It includes IPSecurity, which offers data integrity and secrecy.
  • Route effectiveness
  • Most notably, it is the last resort for the Global-network’s expanding nodes.

Disadvantages of IPv6

Despite having so many advantages, Internet Protocol version 6 also have some disadvantages –

  • The widespread use of IPv4 at the moment makes the conversion to IPv6 unfavourable in that it will take time to accomplish.
  • Communication is not possible between IPv4 and IPv6 devices directly. To do that, they require an intermediary technology.

Frequently Asked Questions

Q1 – What is the IPv6 used for?

IPv6 is used to provide a significantly larger address space, enhanced security features, and improved network performance. It enables seamless communication and connectivity between devices, accommodating the growing number of internet-connected devices and facilitating the development of innovative technologies and services.

Q2 – What is IPv6 in simple terms?

Internet Protocol version 6, in simple terms, is the latest version of the Internet Protocol (IP) that provides a much larger number of unique addresses for devices connecting to the internet. It ensures that there are enough addresses to accommodate the increasing number of devices and allows for better security and performance in communication between these devices.

Q3 – What is IPv6 vs IPv4?

IPv6 and IPv4 are different versions of the Internet Protocol (IP) used to identify and communicate with devices on the internet. IPv4 has a 32-bit address format, limiting the number of available unique addresses, while Internet Protocol version 6 has a 128-bit address format, providing a significantly larger address space to accommodate the growing number of internet-connected devices.

Q4 – What are the 3 types of IPv6 addresses?

The three types of Internet Protocol version 6 addresses are:

  • Unicast Address: Used for communication between a single source and a single destination device.
  • Multicast Address: Used for communication from a single source to multiple destination devices.
  • Anycast Address: Assigned to multiple devices, but the communication is routed to the nearest device in the group, ensuring efficient and optimal routing.


In conclusion, we can say that IPv6 represents a significant advancement in internet protocol technology, overcoming all the limitations of IPv4. With its larger address space, enhanced security features, and improved network performance, IPv6 is sufficient to meet the growing demands of the connected world.

Internet Protocol versions 6 is an integral part of the CCNA training.

Embracing Internet Protocol version 6 adoption will support a fully connected and interoperable internet, unlocking new possibilities for communication, collaboration, and digital advancements in the evolving digital landscape.

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