An address scope defines the region where an address can be defined as a unique identifier of an interface. These scopes or regions are the link, the site network, and the global network, corresponding to link-local, unique local unicast, and global addresses.

Global unicast addresses are:

• Routable and reachable across the Internet.

• IPv6 addresses for widespread generic use.

• Structured as a hierarchy to allow address aggregation.

• Identified by their three high-level bits set to 001 (2000::/3).

The global routing prefix is assigned to a service provider by the Internet Assigned Numbers Authority (IANA). The site level aggregator (SLA), or subnet ID, is assigned to a customer by their service provider. The LAN ID represents individual networks within the customer site and is administered by the customer.

The Host or Interface ID has the same meaning for all unicast addresses. It is 64 bits long and is typically created by using the EUI-64 format.

Example:

2001:0DB8:BBBB:CCCC:0987:65FF:FE01:2345

Unique local unicast addresses are:

• Analogous to private IPv4 addresses (for example, 10.1.1.254)

• Used for local communications, inter-site VPNs, and so forth

• Not routable on the Internet (routing would require IPv6 NAT)

Global IDs do not have to be aggregated and are defined by the administrator of the local domain. Subnet IDs are also defined by the administrator of the local domain. Subnet IDs are typically defined using a hierarchical addressing plan to allow for route summarization.

The Host or Interface ID has the same meaning for all unicast addresses. It is 64 bits long and is typically created by using the EUI-64 format.

Example:

FD00:aaaa:bbbb:CCCC:0987:65FF:FE01:2345

Link local unicast addresses are:

• Mandatory addresses that are used exclusively for communication between two IPv6 devices on the same link.

• Automatically assigned by device when IPv6 is enabled.

• Not routable addresses. Their scope is link-specific only.

• Identified by the first 10 bits (FE80).

The remaining 54 bits of the network ID could be zero or any manually configured value. The interface ID has the same meaning for all unicast addresses. It is 64 bits long and is typically created by using the EUI-64 format.

Example:

FE80:0000:0000:0000:0987:65FF:FE01:2345

This address would generally be represented in shorthand notation as:

FE80::987:65FF:FE01:2345

IPv6 multicast addresses have an 8-bit prefix, FF00::/8 (1111 1111). The second octet defines the lifetime and scope of the multicast address.

Note	IPv6 clients do not require a default gateway configuration because routers are discovered using RSs and RAs.

For more information on IPv6 multicast addresses, refer to the IANA documentation: Link.

Note	IPv6 multicast application is not developed in Collaboration products, and is not supported industry wide through service provider networks.

Because IPv6 addresses are so complex, you won't want to configure many of them manually. There's too much administrative overhead. But you might want static addresses for router interfaces and certain network resources.

One of the easiest ways to assign IP addresses is to set up IPv6 Stateless address auto-configuration (SLAAC) on an IPv6 router.

The network administrator configures the router to send Router Advertisement (RA) announcements onto the link. Then the on-link connected IPv6 nodes configure themselves with an IPv6 address and routing parameters.

They get the IPv6 network prefix from the link-local router's RAs. They create the IPv6 host ID by using the device's MAC address and the EUI-64 format for host IDs.

IPv6 devices use multicast to acquire IP addresses and to find DHCPv6 servers. The basic DHCPv6 client-server concept is similar to DHCP for IPv4. If a client wants to receive configuration parameters, it sends out a request on the attached local network to detect available DHCPv6 servers.

• The DHCPv6 client requests parameters from an available server. This is done using Solicit and Advertise message and well-known DHCPv6 multicast addresses.

• The server responds with the requested information in a Reply message. As with DHCPv4, DHCPv6 uses an architectural concept of "options" to carry more parameters and information within DHCPv6 messages.

The DHCPv6 client knows whether to use DHCPv6 based upon the instruction from a router on its link-local network. The default gateway has two configurable bits in its Router Advertisement (RA) available for this purpose:

• O bit—When this bit is set, the client can use DHCPv6 to retrieve other configuration parameters (for example, TFTP server address or DNS server address) but not the client's IP address.

• M bit—When this bit is set, the client can use DHCPv6 to retrieve a managed IPv6 address and other configuration parameters from a DHCPv6 server.

To automatically configure IP phones with IPv6 address assignment, use the following configuration in Unified CM and in router Routing Advertisement (RA).