1.9 Describe IPv6 address types

Unicast Addresses

Unicast addresses in IPv6 are used for one-to-one communication between devices. There are three main types of unicast addresses:

Global Unicast Addresses

These are unique addresses that are routable on the global Internet. They are analogous to public IPv4 addresses.

Structure: They start with the prefix 2000::/3, followed by a hierarchical structure for routing.

Usage: Used for communication across different networks, such as accessing websites or connecting to remote servers.

Unique Local Addresses (ULAs)

ULAs are designed for local communication within a site or between a limited set of sites. They are not routable on the global Internet, similar to private IPv4 addresses.

Structure: They begin with the prefix FC00::/7, which is subdivided into FC00::/8 (reserved for future use) and FD00::/8 (for local use).

Usage: Ideal for internal network communication and private addressing.

Link-Local Addresses

These addresses are used for communication between nodes on the same link (local network segment). They are not routable beyond the local network.

Structure: They start with the prefix FE80::/10.

Usage: Essential for functions like automatic address configuration and network discovery protocols. They are automatically assigned to each network interface.

Anycast Addresses

Anycast addresses are assigned to multiple interfaces, but packets sent to an anycast address are delivered to the nearest interface (in terms of routing distance).

Structure: Anycast addresses can fall within the global unicast address space, but they are used in routing protocols to identify multiple devices providing the same service.

Usage: Commonly used in services like content delivery networks (CDNs) and DNS, where it’s beneficial to route requests to the closest server.

Multicast Addresses

Multicast addresses are used to send a single packet to multiple destinations at once. This is efficient for broadcasting data to a group of devices.

Structure: Multicast addresses start with the prefix FF00::/8, with further subcategories based on the scope of the multicast group (e.g., link-local, site-local, or global).

Usage: Used for applications like video conferencing or streaming media, where the same data needs to be delivered to multiple recipients simultaneously.

Modified EUI-64

Modified EUI-64 is a method for generating IPv6 interface identifiers based on the MAC address of the interface. This technique ensures that the interface identifier is unique.

Structure: The MAC address is split into two halves and then combined with a fixed prefix to form a 64-bit interface identifier. The 7th bit of the MAC address (the universal/local bit) is flipped to indicate uniqueness.

Usage: Often used in the creation of link-local addresses and for stateless address autoconfiguration.

Summary

IPv6 addresses come in several types, each serving distinct purposes:

• Unicast Addresses: Include global, unique local, and link-local types, each suited for different communication scopes.
• Anycast Addresses: Provide a mechanism for routing data to the nearest of several potential destinations.
• Multicast Addresses: Efficiently distribute data to multiple recipients simultaneously.
• Modified EUI-64: A method for generating unique interface identifiers based on MAC addresses.

Understanding these address types is essential for designing and managing IPv6 networks effectively.