- Aggregatable global unicast addresses are IPv6 addresses used for the generic IPv6 traffic on the IPv6 Internet.
- Aggregatable global unicast addresses are similar to the unicast addresses used to communicate across the IPv4 Internet.
- Aggregatable global unicast addresses represent the most important part of the IPv6 addressing architecture.
- The structure of aggregatable global unicast enables a strict aggregation of routing prefixes to limit the size of the global Internet routing table.
Each aggregatable global unicast IPv6 address has three parts:
Prefix received from a provider— The prefix assigned to an organization (leaf site) by a provider should be at least a /48 prefix, as recommended in RFC 3177, IAB/IESG Recommendations on IPv6 Address Allocations to Sites. The /48 prefix represents the high-order 48-bit of the network prefix. Moreover, the prefix assigned to the organization is part of the provider's prefix.
Site— With one /48 prefix allocated to an organization by a provider, it is possible for that organization to enable up to 65,535 subnets (assignment of 64-bit's prefix to subnets). The organization can use bits 49 to 64 (16-bit) of the prefix received for subnetting.
Host— The host part uses each node's interface identifier. This part of the IPv6 address, which represents the address's low-order 64-bit, is called the interface ID.