TP-Link T2600G-28TS User Manual page 191

IPv6 unicast address is an identifier for a single interface. It consists of a subnet prefix and an
interface ID.
Subnet Prefix: This section is allocated by the IANA (The Internet Assigned Numbers

Authority), the ISP (Internet Service Provider) or the organizations.
Interface ID: An interface ID is used to identify interfaces on a link. The interface ID must be

unique to the link.
There are several ways to form interface IDs. The IPv6 addresses with format prefixes 001
through 111, except for multicast addresses (1111 1111), are all required to have 64-bit
interface IDs in EUI-64 format.
For all IEEE 802 interface types (for example, Ethernet and FDDI interfaces), Interface IDs in
the modified EUI-64 format are constructed in the following way:
The first three octets (24 bits) are taken from the Organizationally Unique Identifier (OUI) of the
48-bit link-layer address (the MAC address) of the interface, the fourth and fifth octets (16 bits)
are a fixed hexadecimal value of FFFE, and the last three octets (24 bits) are taken from the
last three octets of the MAC address. The construction of the interface ID is completed by
setting the universal/local (U/L) bit--the seventh bit of the first octet--to a value of 0 or 1. A
value of 0 indicates a locally administered identifier; a value of 1 indicates a globally unique
IPv6 interface identifier.
Take MAC address 0012:0B0A:2D51 as an example. Insert FFFE to the middle of the address
to get 0012:0BFF:FE0A:2D51. Then set the U/L bit to 1 to obtain an interface ID in EUI-64
format as 0212:0BFF:FE0A:2D51.
IPv6 unicast address can be classified into several types, as shown in Table 10-1. The two
most common types are introduced below:
Global unicast address
A Global unicast address is an IPv6 unicast address that is globally unique and is routable on
the global Internet.
Global unicast addresses are defined by a global routing prefix, a subnet ID, and an interface
ID. The IPv6 global unicast address starts with binary value 001 (2000::/3). The global routing
prefix is a value assigned to a site (a cluster of subnets/links) by IANA. The subnet ID is an
identifier of a subnet within the site.
The figure below shows the structure of a global unicast address.
Figure 10-1 Global Unicast Address Format
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