IPv6 supports various address types to cater to specific functions and requirements of IPv6 networks while serving distinct purposes. This flexibility optimizes network operations, enhancing efficiency and enabling diverse applications on the Internet of Things (IoT) and beyond. IPv6 allows for three basic types of addresses, each with a specific set of rules about its construction and use:
- Unicast address: This address identifies a single network interface. It is typically assigned to devices for direct communication or, in other words, one-to-one communication.
- Multicast Address: Used for one-to-many communication, multicast addresses allow data to be delivered to multiple devices simultaneously. Devices interested in the data join the multicast group.
- Anycast Address: Anycast addresses are assigned to multiple interfaces, but data is routed to the nearest interface. Therefore, this method is also known as one-to-nearest. This improves efficiency and load distribution and is frequently used for services such as Domain Name System or DNS.
NOTE: IPv6 does not support broadcast addresses in the same way that IPv4 does. Instead, specific multicast addresses are used (such as the all-nodes multicast address).
In addition to these three main address types, the IPv6 protocol uses other types, such as:
- Loopback Address: This address is similar to 127.0.0.1 in IPv4 and is identified as “::1”. It allows a device to communicate with itself to test and diagnose itself.
- Link-Local Addresses: Required for communication within a single network segment, link-local addresses allow devices on the same link to interact even when global connectivity is unavailable. The Link-Local Address is critical in networking because it allows communication within a single network segment without needing external routing. It is automatically configured and is required for neighbor discovery and initial network configuration. This address type allows devices on the same local network to connect quickly, ensuring efficient local communication and seamless interaction between neighboring devices. The link-local address uses the “fe80::/10” value.
- Global Unicast Address: These addresses are routable across the internet and used for devices requiring direct external communication. They are equivalent to public IPv4 addresses. The global address uses the “2003::/3” value.
- Unique Local Address (ULA): ULA is a private IPv6 address that allows devices within a specific organization to communicate without exposing internal topology to the global internet. They are analogous to private IPv4 addresses and use the “fc00::/7” value.
IPv6 Address Scopes and Prefixes
Address scopes and prefixes are critical in defining the reach and context of addresses in IPv6-enabled networks. As you can see in the image below, these IPv6 scopes have different area coverage and special purpose in the networks. They improve address management, optimize routing, and allow greater flexibility in tailoring communication based on geographical and organizational contexts.
The interface-local scope is useful for self-referencing because it applies to communication within a specific interface. Link-local addresses are limited to a single network link, making neighbor discovery and configuration easier. Site-local addresses, like private addressing in IPv4, are intended for communication within a site, while within a larger organization, organization-local addresses are important. Finally, the global scope covers the entire internet, allowing global connectivity.