11.3.4 IP Version 6

Overview of IPv6

• The increasing number of connected devices necessitates unique IP addresses for internet connectivity.
• IPv4, using 32-bit addresses, has a limited capacity of approximately 4.3 billion combinations, leading to address exhaustion.
• An effort to develop a new addressing standard, IPv6, began in the mid-1990s.

IPv6 Address Format

• IPv6 addresses consist of 128-bits divided into eight 16-bit blocks, represented by four hexadecimal digits.
• Each block is separated by a colon, allowing for approximately 340 undecillion (340 trillion trillion) unique addresses.
• Simplification rules include removing leading zeros and replacing consecutive blocks of zeros with a double colon (only once per address).

Components of IPv6 Address

• An IPv6 address has two main parts: the prefix (left) and the interface ID (right).
• The prefix functions like a network ID in IPv4, while the interface ID is comparable to host ID.
• The first 48 bits define the site prefix assigned by the ISP, followed by a 16-bit subnet ID indicating the connected network.
• The last 64 bits create the interface ID, which can be derived from a MAC address through a method known as modified EUI-64.

Types of IPv6 Addresses

• Unicast addresses identify a single device and are the most commonly assigned type.

Link-Local Address

• Uses the FE80::/10 prefix for sending and receiving packets within a local network without routers.
• Mandatory for all IPv6 hosts, allowing multiple addresses per interface for automatic configuration and neighbor discovery.

Global Unicast Address

• Corresponding to IPv4 public addresses, these use the 2000::/3 prefix to facilitate data packet transmission over the internet.

Unique Local Address

• Functioning similarly to IPv4 private IPs, these utilize the FC00::/7 prefix, with the following 40 bits forming a randomly generated Global ID.
• Not routable on the internet, they are restricted to internal networks.

Multicast Addresses

• Packets sent to multicast addresses are forwarded to a group of interfaces, designated by an FF00::/8 prefix.
• Local restricted multicast addresses (FF02::/16) do not forward to other networks, akin to IPv4 broadcast addresses; however, IPv6 lacks broadcast addresses.

Anycast Addresses

• Anycast addresses function as unicast addresses assigned to multiple devices, routing packets to the nearest interface.
• An example use is with root DNS servers worldwide, where requests are directed to the closest server.

Loopback Address

• The IPv6 loopback address is represented as all zeros with a final one (e.g., ::1), used primarily for testing inter-service communications on the same host.

Summary Points

• IPv6 features a complex addressing format allowing immense address capacity and includes various address types to suit different networking needs.
• Understanding the structure and capabilities of IPv6 is essential as the shift from IPv4 becomes increasingly prevalent due to address shortages.