1-5z Unassigned address: The unicast address :: is called the unassigned address and may not beassigned to any node. Before acquiring a valid IPv6 address, a node may fill this address in thesource address field of an IPv6 packet, but may not use it as a destination IPv6 address.Multicast addressMulticast addresses listed in Table 1-2 are reserved for special purpose.Table 1-2 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 addressBesides, there is another type of multicast address: solicited-node address. The solicited-nodemulticast address is used to acquire the link-layer addresses of neighbor nodes on the same link and isalso used for duplicate address detection. Each IPv6 unicast or anycast address has onecorresponding solicited-node address. The format of a solicited-node multicast address is as follows:FF02:0:0:0:0:1:FFXX:XXXXWhere, FF02:0:0:0:0:1:FF is permanent and consists of 104 bits, and XX:XXXX is the last 24 bits of anIPv6 address.Interface identifier in IEEE EUI-64 formatInterface identifiers in IPv6 unicast addresses are used to identify interfaces on a link and they arerequired to be unique on that link. Interface identifiers in IPv6 unicast addresses are currently requiredto be 64 bits long. An interface identifier is derived from the link-layer address of that interface. Interfaceidentifiers in IPv6 addresses are 64 bits long, while MAC addresses are 48 bits long. Therefore, thehexadecimal number FFFE needs to be inserted in the middle of MAC addresses (behind the 24high-order bits).To ensure the interface identifier obtained from a MAC address is unique, it isnecessary to set the universal/local (U/L) bit (the seventh high-order bit) to “1”. Thus, an interfaceidentifier in EUI-64 format is obtained.Figure 1-2 Convert a MAC address into an EUI-64 address
