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IPv4 vs IPv6: Internet Protocol Versions Explained Featured Image

IPv4 vs IPv6: Internet Protocol Versions Explained

by: Hostwinds Team  /  March 22, 2024

Main Differences Between IPv4 and IPv6

While their primary purpose is to accurately identify, send and receive data across the internet,  There are a number of key differences between IPv4 and IPv6.

Address Format

IPv4 uses a 32 bit format and is represented by 4 numerical values called octets, separated by  dotted-decimal notation. This format allows for around 4.3 billion unique addresses.

Here's what a typical IPv4 address looks like:

IPv6 addresses use a 128 bit format and are composed of eight 16-bit hexadecimal segments known as "hextet," separated by colons (:). Each hextet can have an alphanumeric value ranging from 0000 to FFFF, allowing for approximately 340 undecillion unique addresses.

Here's what a typical IPv6 address looks like: 2001:0db8:85a3:0000:0000:8a2e:0370:7334

If there are consecutive groups of zeros, the address could be shortened as  2001:0db8:85a3::8a2e:0370:7334 - this is known as zero compression.

Address Configuration

IPv4 addresses are often configured manually or assigned dynamically using protocols like Dynamic Host Configuration Protocol (DHCP).

IPv6 addresses can be assigned through stateless autoconfiguration, where devices generate their own addresses based on network prefixes, or through DHCPv6 (Dynamic Host Configuration Protocol for IPv6).

Header Structure

IPv4 headers are fixed in size and contain fields such as source and destination addresses, header length, and type of service.

IPv6 headers are more simplified and have a fixed size of 40 bytes. They include fields such as source and destination addresses, traffic class, flow label, and next header.


IPv4 has three main subnetwork classes (A, B, and C), each defining the size of the network. Class A addresses are used for large networks, Class B is used for medium-sized networks, and Class C is used for small networks.

Instead of classes, IPv6 utilizes the length of the network prefix to determine the size of the subnetwork. For example, the network "2001:0db8:85a3:0000::/48" is saying the first 48 bits of the address are the fixed network prefix (i.e. cannot change) but the remaining 80 bits can be broken down into subnets.


IPv4 does not include native support for IPsec (Internet Protocol Security), requiring additional protocols and configurations for secure communication.

IPv6 includes built-in support for IPsec, providing a framework for secure communication and authentication between devices on the internet.

Network Communication

IPv4 supports unicast for one-to-one communication, multicast for one-to-many communication and broadcast for one-to-all communication.

IPv6 supports unicast, multicast and anycast communication. Instead of using broadcast, IPv6 primarily relies on multicast to serve the functionalities of both multicast and broadcast in IPv4.

Anycast utilizes one-to-nearest communication, where data packets are sent from one sender to the nearest of several receivers sharing the same anycast address.

Similarities Between IPv4 and IPv6

Internet Protocol Functionality

Both IPv4 and IPv6 serve as the fundamental protocols for communication on the internet, providing the addressing and routing mechanisms necessary for data transmission.

Packet-based Communication

Both IPv4 and IPv6 organize data into packets for transmission over networks. These packets contain header information, including source and destination addresses, to ensure proper routing and delivery.

Connectionless Data Transmission

IPv4 and IPv6  both utilize connectionless communication as part of the Internet Protocol (IP) suite. Each packet is routed independently across the network, and routers make forwarding decisions based solely on the destination address contained within the packet header.

Use of Network Devices

IPv4 and IPv6 packets are processed and routed by similar networking devices, such as routers and switches, enabling interoperability between the two protocols in mixed networks.

Why Move to IPv6?

Address Exhaustion: IPv4 address space is limited and has been exhausted in many regions, making it challenging to obtain new IPv4 addresses. IPv6 offers a vastly larger address space, providing an abundance of addresses to accommodate the growing number of internet-connected devices.

Scalability: IPv6's larger address space allows for better scalability, enabling the continued growth of the internet and the proliferation of new devices without the constraints imposed by IPv4 address shortages.

Efficiency: IPv6 eliminates the need for techniques like Network Address Translation (NAT) used in IPv4 to conserve address space. NAT can introduce complexities and limitations, such as difficulty in peer-to-peer communication and increased administrative overhead. IPv6's abundant address space simplifies network administration and enhances end-to-end connectivity.

Security: IPv6 includes built-in support for IPsec (Internet Protocol Security), providing enhanced security features compared to IPv4. IPsec can be used to encrypt and authenticate IPv6 traffic, ensuring confidentiality, integrity, and authenticity of data transmitted over the network.

Future-Proofing: IPv6 is designed to address the limitations and challenges of IPv4 and accommodate future technological advancements and requirements. As the internet evolves and new technologies emerge, IPv6 provides a robust foundation for continued innovation and growth.

Reasons to Stick with IPv4

Compatibility: IPv6 is not backward compatible with IPv4, meaning that IPv6-only devices cannot communicate directly with IPv4-only devices without translation mechanisms such as dual-stack or protocol translation gateways. This can introduce complexity and compatibility issues in heterogeneous network environments.

Transition Challenges: Migrating from IPv4 to IPv6 can be a complex and time-consuming process, requiring updates to network infrastructure, devices, and applications. Organizations may be reluctant to invest in the transition due to concerns about compatibility, costs, and disruptions to existing operations.

Lack of Support: Some legacy devices, applications, and network equipment may not fully support IPv6 or may require updates or replacements to work with IPv6. This can present obstacles for organizations with legacy systems that rely heavily on IPv4.

Address Management: While IPv6 offers a larger address space, managing IPv6 addresses may be more challenging than IPv4 due to the hexadecimal representation and the sheer number of available addresses. Organizations may need to invest in new tools and processes for IPv6 address management.

Security Concerns: While IPv6 includes built-in support for IPsec, the implementation and deployment of IPsec in IPv6 networks may vary, leading to potential security vulnerabilities if not properly configured. Additionally, the larger address space in IPv6 may make it more difficult to scan and manage address space, potentially complicating network security measures.

Infrastructure Investments: Many organizations have made significant investments in IPv4 infrastructure, including hardware, software, and expertise. Transitioning to IPv6 may require additional investments and resources, which some organizations may be hesitant to allocate.

What is Internet Protocol?

Internet protocol (IP) is a system of rules (protocols) that allow computers, domains and other devices to connect, communicate, and share information over the internet or a local network.

What is an IP Address?

An IP address is a unique string of numbers used to identify devices and domains wanting to use the IP system. These numeric identifiers are basically the home address of a device, making them an essential component for routing data packets to the correct destinations across the internet.

IPv4 and IPv6 are two versions of IP address formats used within the Internet Protocol (IP) system.

Written by Hostwinds Team  /  March 22, 2024