TP-Link T2500-28TCTL-SL5428E T2500-28TCUN V1 User Guide - Page 30
Take MAC address 0012:0B0A:2D51 as an example. Insert, Global Unicast Address Format
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Figure 4-8 Global Unicast Address Format An interface ID is used to identify interfaces on a link. The interface ID must be unique to the link. It may also be unique over a broader scope. In many cases, an interface ID will be the same as or based on the link-layer address of an interface. Interface IDs used in global unicast and other IPv6 address types must be 64 bits long and constructed in the modified extended universal identifier (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 media access control, or 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. Link-local address A link-local address is an IPv6 unicast address that can be automatically configured on any interface using the link-local prefix FE80::/10 (1111 1110 10) and the interface identifier in the modified EUI-64 format. Link-local addresses are used in the neighbor discovery protocol and the stateless autoconfiguration process. Nodes on a local link can use link-local addresses to communicate; the nodes do not need globally unique addresses to communicate. The figure below shows the structure of a link-local address. Figure 4-9 Link-local Address Format IPv6 devices must not forward packets that have link-local source or destination addresses to other links. 20