1-4There are no broadcast addresses in IPv6. Their function is superseded by multicast addresses.The type of an IPv6 address is designated by the format prefix. Table 1-1 lists the mapping betweenmajor address types and format prefixes.Table 1-1 Mapping between address types and format prefixesType Format prefix (binary) IPv6 prefix IDUnassigned address 00...0 (128 bits) ::/128Loopback address 00...1 (128 bits) ::1/128Link-local address 1111111010 FE80::/10Site-local address 1111111011 FEC0::/10UnicastaddressGlobal unicast address other forms —Multicast address 11111111 FF00::/8Anycast address Anycast addresses are taken from unicast address space and arenot syntactically distinguishable from unicast addresses.Unicast addressThere are several forms of unicast address assignment in IPv6, including global unicast address,link-local address, and site-local address.z The global unicast address, equivalent to an IPv4 public address, is used for aggregatable linksand provided for network service providers. This type of address allows efficient routingaggregation to restrict the number of global routing entries.z The link-local address is used in the neighbor discovery protocol and the statelessautoconfiguration process. Routers must not forward any packets with link-local source ordestination addresses to other links.z IPv6 unicast site-local addresses are similar to private IPv4 addresses. Routers must not forwardany packets with site-local source or destination addresses outside of the site (equivalent to aprivate network).z Loopback address: The unicast address 0:0:0:0:0:0:0:1 (represented in shorter format as ::1) iscalled the loopback address and may never be assigned to any physical interface. Like theloopback address in IPv4, it may be used by a node to send an IPv6 packet to itself.z 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.
