Chapter 1 - IPv6 Addressing (Recap)

Introduction to IPv6 Addressing

  • This chapter focuses on the introduction of IPv6 addressing and its importance in network communication.

IPv4 Issues

Current Challenges with IPv4

  • IPv4 address depletion is a significant issue, necessitating the move to IPv6.

  • IPv4 Limitations: Limited address space, NAT complications, and increasing Internet usage create an urgent need for IPv6.

Transition to IPv6

  • IPv6 addresses the limitations of IPv4 with a larger 128-bit address space and improved functionalities.

  • Transitioning strategies include:

    • Dual Stack: Running both IPv4 and IPv6 stacks on devices.

    • Tunneling: Allows IPv6 packets to be sent over an IPv4 network.

    • Translation: Uses NAT64 to facilitate communication between IPv6 and IPv4 systems, enabling a gradual transition to IPv6.

IPv6 Address Representation

Address Format

  • IPv6 addresses are 128 bits and represented in hexadecimal format, case-insensitive.

  • Preferred Format: xxxx:x, where each x is a hextet (16 bits or four hexadecimal digits).

  • Example: 2001:0db8:0000:1111:0000:0000:0000:0200

Notation Rules

Rule 1: Omit Leading Zeros

  • Any leading zeroes in an IPv6 address can be omitted for simplicity:

    • 01ab → 1ab

    • 09f0 → 9f0

Rule 2: Use of Double Colon

  • A contiguous string of hextets consisting entirely of zeros can be replaced by a double colon (::) once in the address.

    • 2001:db8:cafe:1:0:0:0:1 → 2001:db8:cafe:1::1

IPv6 Address Types

Major Address Types

  1. Unicast: Identifies a single unique interface on a device.

  2. Multicast: Sends a single packet to multiple destinations.

  3. Anycast: Address assigned to multiple devices; the packet is routed to the nearest one.

IPv6 Prefix Length

  • Indicates the network part of the address in slash notation (e.g., /64 recommended for LANs).

Unicast Addressing

  • Two key types of IPv6 unicast addresses are:

    • Global Unicast Address (GUA): Internet-routable addresses.

    • Link-local Address (LLA): Used for local communication, not routable outside the link.

Unique Local Address (ULA)

  • Similar to private IPv4 addresses, but for local communication between limited sites; not globally routable.

IPv6 GUA Structure

  • Global Routing Prefix: Assigned by the ISP, varies by provider.

  • Subnet ID: Identifies subnets within an organization.

  • Interface ID: Similar to host part of an IPv4 address.

Static Configuration for IPv6

Configuring GUAs on Routers & Hosts

  • IPv6 configuration commands resemble IPv4, merely replacing ip with ipv6.

  • GUI example for configuring GUA on a router interface:

    R1(config)# interface gigabitethernet 0/0/0
R1(config-if)# ipv6 address 2001:db8:acad:1::1/64
R1(config-if)# no shutdown

Windows Host Configuration

  • Can manually configure an IPv6 address using similar commands to IPv4 settings. Best practice is to use the router's LLA as the default gateway.

Dynamic Addressing for IPv6 GUAs

Methods of Dynamic Addressing

  1. SLAAC: Configures a GUA automatically using Router Advertisements (RAs).

  2. SLAAC with Stateless DHCPv6: Utilizes both SLAAC and a stateless DHCPv6 for DNS and other configurations.

  3. Stateful DHCPv6: Similar to traditional DHCP, allowing devices to receive specific IP addresses and configurations from a DHCP server.

EUI-64 Process

  • Generates an interface ID by embedding a specific value into the MAC address, maintaining uniqueness.

Dynamic Addressing for IPv6 LLAs

  • LLAs are crucial for devices on the same link, automatically generated or configured.

  • Devices need a unique link-local address within the fe80::/10 range.

Cisco Routers and Dynamic LLAs

  • Cisco devices automatically generate LLAs when a GUA is assigned, using the EUI-64 method unless manually set otherwise.

IPv6 Multicast Addresses

Assigned Multicast Addresses

  • Multicast addresses are recognized by the prefix ff00::/8, used for sending data to multiple devices.

Types of Multicast Addresses

  • Well-Known Addresses: Reserved for specific device groups, such as:

    • ff02::1: All-nodes multicast group.

    • ff02::2: All-routers multicast group.

Solicited-Node Multicast Addresses

  • Used by devices to monitor messages sent to them, allowing efficient filtering at the Ethernet level.

IPv6 Neighbor Discovery

Neighbor Discovery Protocol (NDP)

  • Allows automatic configuration of IPv6 addresses and MAC address discovery through ICMPv6 messages.

  • Key messages include Router Solicitation (RS) and Neighbor Solicitation (NS).

Address Resolution Mechanism

  • NDP resolves MAC addresses corresponding to known IPv6 addresses, replacing IPv4's ARP functionality.

Subnetting an IPv6 Network

Subnetting Overview

  • IPv6 was designed for efficient subnetting, using a separate subnet ID within GUA.

Example of Subnetting

  • With a /48 prefix, an organization can create thousands of /64 subnets, offering ample addressing space.