108• Link-local addresses are used for communication among link-local nodes for neighbor discoveryand stateless autoconfiguration. Packets with link-local source or destination addresses are notforwarded to other links.• Site-local unicast addresses are similar to private IPv4 addresses. Packets with site-local source ordestination addresses are not forwarded out of the local site (or a private network).• A loopback address is 0:0:0:0:0:0:0:1 (or ::1). It cannot be assigned to any physical interface andcan be used by a node to send an IPv6 packet to itself in the same way as the loopback addressin IPv4.• An unspecified address is 0:0:0:0:0:0:0:0 (or ::). It cannot be assigned to any node. Beforeacquiring a valid IPv6 address, a node fills this address in the source address field of IPv6 packets.The unspecified address cannot be used as a destination IPv6 address.Multicast addressesIPv6 multicast addresses listed in Table 8 are reserved for special purposes.Table 8 Reserved IPv6 multicast addressesAddress ApplicationFF01::1 Node-local scope all-nodes multicast addressFF02::1 Link-local scope all-nodes multicast addressFF01::2 Node-local scope all-routers multicast addressFF02::2 Link-local scope all-routers multicast addressFF05::2 Site-local scope all-routers multicast addressMulticast addresses also include solicited-node addresses. A node uses a solicited-node multicastaddress to acquire the link-layer address of a neighboring node on the same link and to detect duplicateaddresses. Each IPv6 unicast or anycast address has a corresponding solicited-node address. The formatof a solicited-node multicast address is FF02:0:0:0:0:1:FFXX:XXXX. FF02:0:0:0:0:1:FF is fixed andconsists of 104 bits, and XX:XXXX is the last 24 bits of an IPv6 unicast address or anycast address.EUI-64 address-based interface identifiersAn interface identifier is 64 bits and uniquely identifies an interface on a link.Interfaces generate EUI-64 address-based interface identifiers differently.• On an IEEE 802 interface (such as a VLAN interface)The interface identifier is derived from the link-layer address (typically a MAC address) of theinterface. The MAC address is 48-bit long. To obtain an EUI-64 address-based interface identifier,insert the hexadecimal number FFFE (16 bits of 1111111111111110) into the MAC address(behind the 24th high-order bit), and set the universal/local (U/L) bit (which is the seventhhigh-order bit) to 1, ensuring that the obtained interface identifier is globally unique.Figure 45 shows how an EUI-64 address-based interface identifier is generated from a MACaddress.
