Internet Protocol Version 6 (IPv6)

This section covers the IPv6 protocol, its routing methods, and addressing mechanisms. IPv6 resolves limitations in IPv4, such as address exhaustion, and introduces new features for more efficient networking, including simplified headers, improved multicast, and integrated security support.

Category

Description

Use Case

IPv6 Basics

Introduction to IPv6, including its address structure, packet format, and differences from IPv4. Highlights features like larger address space, simplified header, and auto-configuration.

Future-ready internet and enterprise networking.

Header Structure

IPv6 uses a simplified, fixed-length 40-byte header for faster processing. It removes non-essential fields like checksum and fragmentation from the base header.

This design improves router efficiency and reduces latency in packet forwarding.

Packet Routing

IPv6 supports hierarchical addressing, which simplifies routing tables. Routing aggregation is enabled through prefix-based design.

Enhances scalability for ISPs and large enterprise networks.

Fragmentation

Fragmentation is performed only by the source device, not intermediate routers. IPv6 uses extension headers to carry fragmentation information.

Reduces router workload and improves overall network performance.

Connectionless Protocol

IPv6 remains a connectionless protocol like IPv4, using best-effort delivery. It does not guarantee packet delivery, ordering, or error correction.

Ideal for applications like streaming and gaming where speed matters more than reliability.

Hop Limit

IPv6 replaces IPv4’s TTL with a Hop Limit field. It defines the maximum number of routers a packet can pass through.

Helps prevent routing loops and ensures timely packet expiration.

Auto Configuration

IPv6 supports Stateless Address Auto-Configuration (SLAAC) and DHCPv6. Devices can generate their own IP addresses using network prefixes and MAC addresses.

Useful for plug-and-play setups, mobile devices, and IoT environments.

Security Integration

IPv6 mandates support for IPsec, unlike IPv4 where it’s optional. IPsec provides encryption, authentication, and data integrity.

Enables secure end-to-end communication across public and private networks.

QoS Support

IPv6 includes a Flow Label field to identify and prioritize traffic flows. It allows routers to handle real-time traffic like VoIP and video more efficiently.

Improves Quality of Service for latency-sensitive applications.

Neighbour Discovery

IPv6 replaces ARP with the Neighbor Discovery Protocol (NDP). NDP uses ICMPv6 for address resolution, router discovery, and reachability detection.

Enhances network efficiency and supports dynamic address changes.

Improved Multicast

IPv6 eliminates broadcast and relies heavily on multicast communication. Scoped multicast addresses reduce unnecessary traffic.

Optimized for group-based services like IPTV and conferencing.

Dual Stack

Dual stack allows devices to run IPv4 and IPv6 simultaneously. Ensures compatibility with legacy systems during the transition phase.

Facilitates gradual migration to IPv6 without disrupting existing services.

Built-in Mobility Support

Mobile IPv6 enables devices to maintain connections while changing networks. It supports seamless handover and session continuity.

Crucial for mobile users, remote workers, and roaming devices.

Anycast Addressing

Allows multiple interfaces to share the same address. Used for nearest-node routing and load balancing.

Efficient routing to the closest of multiple nodes

CIDR (Classless Inter-Domain Routing)

Method for IP address aggregation and efficient routing. Simplifies subnetting and reduces routing table size.

Hierarchical address allocation and subnet management

Multicast Addressing

Enables sending packets to multiple destinations simultaneously. Used for streaming, group communication, and service discovery.

Group communication in local or wide area networks

Subnetting IPv6

Divides IPv6 networks into smaller subnetworks. Improves address organization and traffic management.

Network segmentation and management

Unicast Addressing

Unique address assigned to a single interface. Used for one-to-one communication.

Direct communication between individual devices

NAT (Network Address Translation)

Translates private IP addresses to a public IP address for internet communication. Though less common in IPv6 due to large address space, NAT is used in some IPv6 deployment scenarios.

Conserves public IPv4 addresses, enables internal network privacy, supports IPv4-IPv6 transition

EGP (Exterior Gateway Protocol)

One of the earliest routing protocols used to exchange routing info between autonomous systems.Largely obsolete and replaced by BGP.

Inter-AS routing in early networks.

EIGRP (Enhanced Interior Gateway Routing Protocol)

Cisco proprietary protocol combining features of distance-vector and link-state protocols.Supports VLSM, fast convergence, and uses DUAL algorithm.

Efficient routing within Cisco-based enterprise networks.

IGRP (Interior Gateway Routing Protocol)

Older Cisco proprietary protocol, now deprecated in favor of EIGRP.Limited scalability and slow convergence.

Legacy enterprise routing.

IS-IS (Intermediate System to Intermediate System)

Link-state protocol designed for large ISP networks. Scales well and supports both IPv4 and IPv6.

Core ISP and enterprise backbone routing.

Multiprotocol BGP (MP-BGP)

Extension of BGP that supports routing for multiple protocols, including IPv6 and MPLS VPNs.

Multi-protocol environments and MPLS networks.

OSPF (Open Shortest Path First)

Open standard link-state protocol using Dijkstra’s algorithm.Supports areas, fast convergence, and VLSM.

Hierarchical and scalable enterprise routing.

RIPv1 (Routing Information Protocol v1)

Early distance-vector protocol using hop count metric.No support for CIDR or VLSM.

Small networks or legacy equipment.

RIPv2 (Routing Information Protocol v2)

An enhanced version of RIPv1, supporting authentication, CIDR, and multicast updates.

Small-to-medium networks with basic routing needs.

RFC: RFC 8200 (Obsoletes RFC 2460)

Main Features:

  • 128-bit address space (e.g., 2001:0db8::1) allowing trillions of unique addresses

  • Simplified and fixed-size header (40 bytes) compared to IPv4

  • No need for NAT — end-to-end connectivity and global addressing

  • Built-in support for IPsec, mobility, and auto-configuration (SLAAC)

  • Eliminates broadcast; uses multicast and anycast instead

  • Enhanced quality of service (QoS) with Flow Label field

Use Cases:

  • Modern enterprise and ISP networks

  • IoT and mobile systems requiring a large address pool

  • Future-proofing infrastructure for global internet growth

Alternative Protocols:

  • IPv4 – Legacy version still widely deployed

  • MPLS – Protocol-independent forwarding

  • IPX – Deprecated Novell protocol

Let us learn more about IPv6 Basics:

Jump to “IPv6 Basics”

RFC: RFC 8200 (Obsoletes RFC 2460)

Main Features:

  • Simplified fixed-size header of 40 bytes for efficient processing

  • Eliminates fields like header checksum and fragmentation from the base header

  • Includes fields like Version, Traffic Class, Flow Label, Payload Length, Next Header, Hop Limit, Source and Destination addresses

  • Uses extension headers for optional information and advanced features

  • Designed for faster routing and better scalability compared to IPv4

Use Cases:

  • Network devices needing efficient packet forwarding

  • Routers and firewalls parsing IPv6 headers

  • Protocol analyzers and network diagnostics

Alternative Protocols:

  • IPv4 Header – older, variable length and more complex header structure

  • Other Network Layer protocols like MPLS for specialized routing

Let us learn more about IPv6 Header Structure:

RFC: RFC 8200 (Obsoletes RFC 2460)

Main Features:

  • Uses hierarchical addressing and prefix aggregation for scalable routing

  • Supports route optimization with simplified routing tables

  • Enables efficient path selection based on destination address prefixes

  • Utilizes Next Header field to handle routing extensions and options

  • Compatible with various dynamic routing protocols like OSPFv3, RIPng, and MP-BGP

Use Cases:

  • Efficient routing in ISP and large enterprise networks

  • Scalable internet backbone and multi-homed environments

  • Transition and coexistence with IPv4 networks using dual-stack routing

Alternative Protocols:

  • IPv4 Packet Routing – traditional method with different addressing scheme

  • MPLS – protocol-independent forwarding often used in service provider networks

  • Static routing – for small or controlled environments

Let us learn more about IPv6 Packet Routing:

RFC: RFC 8200 (Obsoletes RFC 2460)

Main Features:

  • Fragmentation is performed only by the source device, not by routers along the path

  • Uses a Fragment extension header to carry fragmentation information

  • Intermediate routers do not fragment packets, reducing processing overhead

  • Enables Path MTU Discovery to avoid fragmentation whenever possible

  • Improves overall network performance and reliability

Use Cases:

  • Transmission of large packets across networks with varying MTU sizes

  • Applications requiring efficient packet delivery without router fragmentation

  • Enhances performance in heterogeneous networks with mixed link capabilities

Alternative Protocols:

  • IPv4 Fragmentation – fragmentation can happen at routers, causing inefficiency

  • Path MTU Discovery mechanisms for both IPv4 and IPv6 to prevent fragmentation

Let us learn more about IPv6 Fragmentation:

RFC: RFC 8200 (Obsoletes RFC 2460)

Main Features:

  • IPv6 is a connectionless protocol like IPv4, delivering packets independently

  • Each packet is routed separately without establishing a session

  • No guarantees on delivery, order, or error correction — best-effort service

  • Simplifies routing and enables scalability for large networks

  • Suitable for real-time applications where speed is prioritized over reliability

Use Cases:

  • Streaming media, VoIP, and online gaming applications

  • DNS queries and other stateless network communications

  • Stateless communication scenarios requiring minimal overhead

Alternative Protocols:

  • Connection-oriented protocols like TCP for reliable communication

  • MPLS for traffic engineering and path management

Let us learn more about IPv6 Connectionless Protocol:

Jump to “IPv6 Connectionless Protocol”

RFC: RFC 8200 (Obsoletes RFC 2460)

Main Features:

  • Replaces the IPv4 Time To Live (TTL) field with Hop Limit in IPv6 headers

  • Specifies the maximum number of hops (routers) a packet can traverse

  • Decremented by one at each router the packet passes through

  • Prevents packets from circulating indefinitely in routing loops

  • Used by diagnostic tools like traceroute to map network paths

Use Cases:

  • Loop prevention in IP networks

  • Network path diagnostics and troubleshooting

  • Ensuring timely packet expiry in multi-hop environments

Alternative Protocols:

  • IPv4 TTL field – similar function in IPv4 packets

  • ICMP messages for reporting expired packets

Let us learn more about IPv6 Hop Limit:

Jump to “IPv6 Hop Limit”

RFC: RFC 4862 (IPv6 Stateless Address Autoconfiguration)

Main Features:

  • Supports Stateless Address Autoconfiguration (SLAAC) allowing devices to configure their own IPv6 addresses automatically

  • Uses Router Advertisements (RAs) to provide network prefix and configuration parameters

  • Also supports stateful configuration via DHCPv6 for more controlled address assignment

  • Enables plug-and-play connectivity without manual IP address configuration

  • Simplifies network management, especially in large or dynamic environments

Use Cases:

  • Mobile devices connecting to IPv6 networks seamlessly

  • IoT devices requiring automatic network setup

  • Enterprise and ISP networks simplifying device onboarding

Alternative Protocols:

  • DHCPv6 for stateful address configuration and additional parameters

  • Manual/static IP configuration for controlled environments

Let us learn more about IPv6 Auto Configuration:

Jump to “IPv6 Auto Configuration”

RFC: RFC 4301 (Security Architecture for IP), RFC 8200 (IPv6)

Main Features:

  • IPv6 mandates support for IPsec for authentication, encryption, and data integrity

  • Provides end-to-end security at the IP layer, unlike IPv4 where IPsec is optional

  • Supports Authentication Header (AH) and Encapsulating Security Payload (ESP) protocols

  • Enhances protection against eavesdropping, tampering, and replay attacks

  • Facilitates secure VPNs, secure communications, and compliance with security policies

Use Cases:

  • Enterprise networks requiring secure communication tunnels

  • VPN deployments and remote access security

  • Regulatory compliance for data privacy and security

Alternative Protocols:

  • TLS/SSL for application-layer security

  • Network layer firewalls and intrusion detection systems

Let us learn more about IPv6 Security Integration:

Jump to “IPv6 Security Integration”

RFC: RFC 8200 (IPv6), RFC 7915 (Flow Label Specification)

Main Features:

  • Includes a Flow Label field in the IPv6 header to identify and manage traffic flows

  • Enables routers to recognize and prioritize packets belonging to specific flows

  • Supports differentiated handling for latency-sensitive applications like VoIP and video streaming

  • Works alongside Traffic Class field for enhanced Quality of Service (QoS) management

  • Helps optimize network performance by prioritizing critical traffic

Use Cases:

  • Real-time communication applications requiring low latency

  • Multimedia streaming and online gaming

  • Enterprise networks with traffic prioritization policies

Alternative Protocols:

  • Differentiated Services (DiffServ) for QoS classification and marking

  • Integrated Services (IntServ) for resource reservation

Let us learn more about IPv6 QoS Support:

Jump to “IPv6 QoS Support”

RFC: RFC 4861 (Neighbor Discovery for IP version 6)

Main Features:

  • Replaces ARP from IPv4 with the Neighbor Discovery Protocol (NDP)

  • Uses ICMPv6 messages for address resolution, router discovery, and neighbor reachability

  • Supports Duplicate Address Detection (DAD) to prevent address conflicts

  • Enables efficient address autoconfiguration and network prefix discovery

  • Enhances network security with Secure Neighbor Discovery (SEND) extensions

Use Cases:

  • Address resolution in IPv6 local networks

  • Router and prefix discovery for auto-configuration

  • Detecting unreachable neighbors and managing link-layer addresses

Alternative Protocols:

  • ARP in IPv4 networks

  • DHCPv6 for additional configuration beyond basic address resolution

Let us learn more about IPv6 Neighbor Discovery:

Jump to “IPv6 Neighbour Discovery”

RFC: RFC 4291 (IPv6 Addressing Architecture), RFC 3810 (MLD for IPv6)

Main Features:

  • Eliminates broadcast traffic, relying on multicast for efficient group communication

  • Supports scoped multicast addresses to limit traffic to specific network regions

  • Uses Multicast Listener Discovery (MLD) protocol for managing multicast group membership

  • Enables optimized delivery of data to multiple receivers without flooding the network

  • Supports applications like IPTV, conferencing, and service discovery

Use Cases:

  • Group communication in local and wide area networks

  • Streaming media and real-time collaboration tools

  • Efficient network resource usage by avoiding unnecessary broadcast traffic

Alternative Protocols:

  • Broadcast in IPv4 networks

  • Application-layer multicast solutions

Let us learn more about IPv6 Improved Multicast:

Jump to “IPv6 Improved Multicast”

RFC: RFC 4213 (Basic Transition Mechanisms for IPv6 Hosts and Routers)

Main Features:

  • Enables devices and networks to run IPv4 and IPv6 protocols simultaneously

  • Allows gradual migration from IPv4 to IPv6 without service disruption

  • Supports both IPv4 and IPv6 address configurations on the same interface

  • Facilitates interoperability between IPv4-only and IPv6-only networks

  • Commonly used in enterprise and ISP transition strategies

Use Cases:

  • Networks and devices transitioning to IPv6

  • Ensuring backward compatibility with legacy IPv4 infrastructure

  • Supporting applications that require both IP versions during migration

Alternative Protocols:

  • Tunneling mechanisms (e.g., 6to4, Teredo)

  • NAT64/DNS64 for IPv6-to-IPv4 translation

Let us learn more about IPv6 Dual Stack:

Jump to “IPv6 Dual Stack”

RFC: RFC 6275 (Mobile IPv6)

Main Features:

  • Enables mobile devices to maintain ongoing IP connections while moving across different networks

  • Supports seamless handover without losing session continuity

  • Uses Home Agent and Care-of Address concepts to route traffic to the mobile node’s current location

  • Integrates with IPv6’s large address space and auto-configuration features

  • Improves user experience for mobile users, remote workers, and IoT devices

Use Cases:

  • Smartphones and tablets switching between Wi-Fi and cellular networks

  • Remote workers maintaining VPN sessions while roaming

  • IoT devices moving across different network domains without reconfiguration

Alternative Protocols:

  • Mobile IPv4 (less efficient and less secure)

  • Proxy Mobile IPv6 (network-based mobility management)

Let us learn more about IPv6 Built-in Mobility Support:

Jump to “IPv6 Built-in Mobility Support”

RFC: RFC 4291

Main Features:

  • Supports aggregation of IP address prefixes

  • Enables variable-length subnet masking

  • Reduces routing table size and improves scalability

Use Cases:

  • Hierarchical address allocation and subnet management

  • Simplifies routing and address delegation

Alternative Approaches:

  • Classful addressing (obsolete)

Let us learn more about CIDR:

Jump to “CIDR”

RFC: RFC 4291, RFC 7421

Main Features:

  • Divides IPv6 prefixes into smaller subnets

  • Recommended subnet size is /64

  • Helps with traffic control and address hierarchy

Use Cases:

  • Network segmentation in enterprise/ISP networks

  • Security policy enforcement

Alternative Approaches:

  • Flat addressing schemes (rare)

Let us learn more about Subnetting IPv6:

Jump to “Subnetting IPv6”

RFC: RFC 3022 (Traditional NAT), RFC 7915 (IPv6-to-IPv4 Translation)

Main Features:

  • Translates private IP addresses to public IP addresses and vice versa

  • Enables multiple devices on a local network to share a single public IP address

  • Helps conserve IPv4 address space and enhances security by hiding internal addresses

  • NAT is not commonly required in IPv6 due to its large address space and global addressing

  • IPv6 supports NAT64 for IPv6-to-IPv4 communication during transition periods

Use Cases:

  • IPv4 networks with limited public IP addresses

  • Home routers and enterprise firewalls managing internal/external traffic

  • IPv6 transition mechanisms requiring IPv4 compatibility

Alternative Protocols:

  • Native IPv6 addressing (no NAT needed)

  • Dual stack and tunneling for IPv4/IPv6 coexistence

Let us learn more about NAT:

Jump to “NAT (Network Address Translation)”

RFC: RFC 4291

Main Features:

  • Multiple interfaces share the same IP address

  • Packets routed to the nearest interface (in terms of routing cost)

  • Used for load balancing and redundancy

Use Cases:

  • Efficient routing to the closest of multiple nodes (e.g., DNS servers, gateways)

Alternative Approaches:

  • Unicast addressing – One-to-one communication

  • Multicast addressing – One-to-many communication

Let us learn more about Anycast Addressing:

Jump to “Anycast Addressing”

RFC: RFC 4291

Main Features:

  • Enables one-to-many communication

  • Replaces broadcast in IPv6

  • Uses address range ff00::/8

  • Used for service discovery and protocol announcements

Use Cases:

  • Group communication in LAN/WAN

  • Streaming, routing protocol updates, neighbor discovery

Alternative Approaches:

  • Broadcast addressing (IPv4 only)

  • Anycast addressing – One-to-nearest communication

Let us learn more about Multicast Addressing:

Jump to “Multicast Addressing”

RFC: RFC 4291

Main Features:

  • Unique address assigned to a single interface

  • Includes global, link-local, and unique local types

  • Enables device-to-device communication

Use Cases:

  • One-to-one communication on IPv6 networks

  • Device identification, routing, and connectivity

Alternative Approaches:

  • Anycast addressing – One-to-nearest communication

  • Multicast addressing – One-to-many communication

Let us learn more about Unicast Addressing:

Jump to “Unicast Addressing”

RFC: RFC 904, RFC 1772 (Historic)

Main Features:

  • One of the earliest routing protocols used to exchange routing info between autonomous systems.

  • Largely obsolete and replaced by BGP.

Use Cases:

  • Inter-AS routing in early networks.

Alternative Protocols:

  • BGP – Modern exterior gateway protocol used globally.

Let us learn more about EGP:

Jump to “EGP”

RFC: RFC 1142, RFC 1195, RFC 5308 (IPv6 support)

Main Features:

  • Link-state protocol designed for large ISP networks.

  • Scales well and supports both IPv4 and IPv6.

Use Cases:

  • Core ISP and enterprise backbone routing.

Alternative Protocols:

  • OSPF – Another scalable link-state protocol.

  • BGP – For inter-domain routing.

Let us learn more about IS-IS:

Jump to “IS-IS”

RFC: RFC 4271 (BGP-4), RFC 4760 (Multiprotocol Extensions)

Main Features:

  • Extension of BGP that supports routing for multiple protocols, including IPv6 and MPLS VPNs.

Use Cases:

  • Multi-protocol environments and MPLS networks.

Alternative Protocols:

  • EIGRP – For internal routing within organizations.

  • IS-IS – Alternative backbone routing protocol.

Let us learn more about MP-BGP:

Jump to “MP-BGP”

RFC: RFC 2328 (OSPFv2)

Main Features:

  • Open standard link-state protocol using Dijkstra’s algorithm.

  • Supports areas, fast convergence, and VLSM.

Use Cases:

  • Hierarchical and scalable enterprise routing.

Alternative Protocols:

  • IS-IS – Another open standard link-state protocol.

  • EIGRP – Cisco proprietary alternative.

Let us learn more about OSPF:

Jump to “OSPF”

RFC: RFC 1058

Main Features:

  • Early distance-vector protocol using hop count metric.

  • No support for CIDR or VLSM.

Use Cases:

  • Small networks or legacy equipment.

Alternative Protocols:

  • RIPv2 – Improved version with modern features.

  • OSPF – For larger or more complex networks.

Let us learn more about RIPv1:

Jump to “RIPv1”

RFC: RFC 2453

Main Features:

  • An enhanced version of RIPv1, supporting authentication, CIDR, and multicast updates.

Use Cases:

  • Small-to-medium networks with basic routing needs.

Alternative Protocols:

  • OSPF – More scalable and feature-rich.

  • EIGRP – Cisco proprietary alternative.

Let us learn more about RIPv2:

Jump to “RIPv2”