IPv6 introduces a new addressing architecture that differs from the familiar dotted-decimal format of IPv4 addresses. The IPv6 addressing architecture includes various address types, a specific address format, and representation rules.
Address Types:
- Unicast Addresses: Unicast addresses identify a single interface within an IPv6 network. They are used for one-to-one communication between a source and a destination. Unicast addresses include Global Unicast Addresses, Link-Local Addresses, and Unique Local Addresses.
- Multicast Addresses: Multicast addresses identify a group of interfaces within an IPv6 network. They are used for one-to-many communication, where a packet is sent to multiple devices simultaneously. Multicast addresses start with the prefix “FF00::/8”.
- Anycast Addresses: Anycast addresses identify a group of interfaces, but the packet is delivered to only one interface—the nearest or best interface in terms of routing metrics. Anycast addresses enable efficient content delivery and load balancing in distributed systems.
Address Format:
IPv6 addresses are written in eight groups of four hexadecimal digits separated by colons (:). Each group represents 16 bits, resulting in a total of 128 bits. An example IPv6 address looks like this: 2001:0db8:85a3:0000:0000:8a2e:0370:7334.
Address Representation:
- Leading Zero Compression: Leading zeros within each group can be omitted to simplify the address representation. For example, 2001:0db8 can be written as 2001:db8.
- Double Colon (::) Notation: Double colons can be used to represent consecutive groups of zeros. They can only be used once within an address. For example, 2001:0db8:0000:0000:0000:0000:1428:57ab can be shortened to 2001:db8::1428:57ab.
- Link-Local Address Representation: Link-local addresses, which are used for communication within a single subnet, have a specific representation. They start with the prefix fe80::/10, and the last 64 bits are derived from the device’s MAC address. The MAC address is converted to 64-bit EUI-64 format, and the seventh bit is inverted.
- Zone ID: In some cases, an IPv6 address may require a zone or interface identifier to identify the specific interface on a device. Zone IDs are typically used in link-local addresses and are indicated by appending “%zone_id” after the address. For example, fe80::1%eth0.
IPv6 addresses are longer and more complex than IPv4 addresses, but they provide a significantly larger address space to accommodate the growing number of devices connected to the internet. The address format and representation rules ensure efficient and concise representation while maintaining the uniqueness and hierarchy of IPv6 addresses.
Here are some additional details about IPv6 addressing architecture:
Address Types (Continued):
- Global Unicast Addresses: Global Unicast addresses are routable IPv6 addresses that are globally unique and can be used for communication across the internet. They are assigned by Internet Assigned Numbers Authority (IANA) to Regional Internet Registries (RIRs), which further allocate them to Internet Service Providers (ISPs) and organizations.
- Link-Local Addresses: Link-Local addresses are used for communication within a single network link or subnet. They are automatically configured by devices using the link-local prefix fe80::/10, followed by the interface identifier derived from the device’s MAC address.
- Unique Local Addresses (ULA): Unique Local Addresses provide a private addressing space within an organization’s network, similar to IPv4’s private IP addresses (e.g., 10.0.0.0/8, 192.168.0.0/16). ULAs are not globally routable and are intended for internal use only. They use the prefix fc00::/7.
Address Format (Continued):
- Subnet Prefix: The first portion of an IPv6 address represents the subnet prefix. It identifies the network or subnet to which the address belongs. The length of the prefix is indicated by the number of bits used. For example, a /64 subnet prefix uses the first 64 bits of the address.
- Interface Identifier: The interface identifier is the unique portion of the address that identifies a specific interface on a network device. In some cases, it is derived from the device’s MAC address using the EUI-64 format. Alternatively, it can be manually assigned or generated using other mechanisms.
Address Representation (Continued):
- IPv4-Compatible Addresses: IPv6 includes a mechanism called IPv4-Compatible Addresses, which allows IPv6 and IPv4 networks to interoperate. These addresses start with the prefix ::/96 and are followed by the 32-bit IPv4 address embedded in the last 32 bits of the IPv6 address.
- IPv4-Mapped Addresses: Similar to IPv4-Compatible Addresses, IPv4-Mapped Addresses provide a representation of IPv4 addresses within an IPv6 format. These addresses start with the prefix ::ffff:0:0/96, followed by the 32-bit IPv4 address.
- Special Addresses: IPv6 reserves certain special addresses, such as the unspecified address (::), loopback address (::1), and multicast addresses (starting with FF00::/8). These addresses serve specific purposes within the IPv6 addressing architecture.
Overall, the IPv6 addressing architecture provides a flexible and scalable framework for addressing devices on the internet. It offers a larger address space, improved hierarchy, and various address types to accommodate the evolving needs of network communication.
