IPv6 - Internet Protocol version 6

What is IPv6?

IPv6 stands for Internet Protocol version 6. It is the successor to IPv4, designed to solve the problem of IP address exhaustion. IPv6 uses 128-bit addresses, allowing for a vastly larger number of unique IP addresses compared to IPv4’s 32-bit system.

Why is IPv6 useful?

  • IPv4 addresses are running out due to the explosion of internet-connected devices.

  • It supports more efficient routing and better security features.

  • It enables end-to-end connectivity without the need for NAT (Network Address Translation).

  • It simplifies network configuration with auto-configuration capabilities.

How it works?

  • Device gets an IPv6 address — either via DHCPv6 or Stateless Address Autoconfiguration (SLAAC).

  • Packets are created with IPv6 headers — including source and destination IPv6 addresses.

  • Routers forward packets — based on the destination IPv6 address.

  • Target device receives data — and processes the packet if the address matches.

Where is IPv6 used?

  • Modern internet infrastructure — ISPs, cloud providers, and large enterprises are adopting IPv6.

  • Mobile networks — many cellular networks use IPv6 by default.

  • IoT devices — IPv6 supports the massive scale of connected devices.

  • Next-gen applications — that require direct, scalable, and secure communication.

Which OSI Layer does IPv6 operate at?

  • IPv6 operates at the Network Layer (Layer 3) of the OSI model.

  • It provides logical addressing and routing between devices across different networks.

  • It encapsulates data into packets and ensures they reach the correct destination.

Is IPv6 Windows specific?

No, IPv6 is not Windows specific. It is supported by all major operating systems, including Windows, Linux, and macOS.

Is IPv6 Linux specific?

No, IPv6 is not Linux specific. It is a standard internet protocol implemented across all modern networked systems.

Which Transport Protocol is used by IPv6?

IPv6 works with multiple transport protocols, primarily TCP and UDP, just like IPv4. It also supports ICMPv6 and others.

Which Port is used by IPv6?

IPv6 does not use a specific port. Applications running over IPv6 use the same port numbers as they would with IPv4 (e.g., HTTP uses port 80, SSH uses port 22).

Is IPv6 using client-server model?

IPv6 supports the client-server model as well as peer-to-peer communication, just like IPv4. It is not restricted to one model of communication.

Topics in this section,

  • In this section, you are going to learn

  • Terminology

  • Version Info

Version & RFC Details

IPv6 Version

RFC Version

Year

Core Idea / Contribution

IPv6

RFC 1883

1995

Original specification of IPv6.

RFC 2460

1998

First major IPv6 specification; introduced 128-bit addressing, simplified headers, extension headers, flow labels.

RFC 4291

2006

Defines IPv6 addressing architecture including unicast, multicast, and anycast addresses.

RFC 4443

2006

Defines ICMPv6, the control messaging protocol for IPv6.

RFC 4861

2007

Specifies Neighbor Discovery Protocol (NDP) for IPv6.

RFC 4862

2007

Defines Stateless Address Autoconfiguration (SLAAC) for IPv6.

RFC 6106

2010

Adds DNS configuration options to Router Advertisements.

RFC 5952

2010

Defines a canonical textual representation format for IPv6 addresses.

RFC 8200

2017

Obsoletes RFC 2460; current standard for IPv6. Clarifies extension headers, flow labels, and updates terminology.

RFC 9386

2023

Provides updated status and deployment insights for IPv6.

  • Setup

IPv6 Packet

S.No

Protocol Packets

Description

Size(bytes)

1

IPv6

141

Header

41

Version

IP version (6 for IPv6)

1

Traffic Class

specifying the priority of the packet.

1

Flow Label

identifying flows of packets.

3

Payload Length

indicating the length of the payload.

2

Next Header

specifying the next level protocol (e.g., TCP, UDP).

1

Hop Limit

maximum number of hops the packet can take.

1

Source IP Address

IP address of the sender.

16

Destination IP Address

IP address of the receiver.

16

Data

actual payload carried by the IP packet.

variable(100)

IPv6 - Use Cases

S.no

Use Case

Description

1

Internet Communication

IPv6 provides a vastly larger address space (128-bit) to support the growing number of internet-connected devices.

2

Enterprise Networking

Used in modern LANs and WANs, especially in organizations transitioning from IPv4 to IPv6 for scalability and future-proofing.

3

Web Hosting & DNS

Websites and services are increasingly hosted with IPv6 addresses; DNS supports AAAA records for IPv6 resolution.

4

End-to-End Connectivity

Eliminates the need for NAT, enabling true peer-to-peer communication and simplifying network configurations.

5

VPN and Remote Access

IPv6 supports secure tunneling and remote access protocols, often coexisting with IPv4 in dual-stack environments.

6

IoT and Smart Devices

IPv6s vast address space allows unique addressing for billions of IoT devices, improving manageability and routing.

7

Stateless Address Autoconfiguration (SLAAC)

Devices can self-configure IP addresses without DHCP, simplifying network setup.

8

Multimedia and Real-Time Services

IPv6 supports efficient multicast and QoS features, enhancing performance for VoIP, video conferencing, and streaming.

IPv6 - Basic Features

S.no

Features

Description

1

128-bit Addressing

Vast address space, enabling trillions of unique IPs.

2

Simplified Header Structure

Fixed 40-byte header with optional extension headers for flexibility.

3

Multicast Support

Efficient one-to-many communication for services like streaming.

4

Stateless Address Autoconfiguration (SLAAC)

Devices can self-configure IPs using router advertisements.

5

Improved Security (IPsec)

Mandatory support for encryption and authentication at the IP layer.

6

Flow Label Field

Allows labeling of packets for special handling.

7

Extension Headers

Modular headers for routing, fragmentation, security, etc.

8

Hop Limit

Replaces IPv4s TTL; limits packet lifetime across routers.

9

Classless Addressing

No address classes (A, B, C); uses CIDR-like prefixing.

10

Efficient Routing

Aggregated prefixes and simplified headers improve routing performance.

  • Reference links