Following are the different unicast addresses that IPv6 supports:
■ Global aggregatable address (also called global unicast address)
■ Link-local address
■ IPv4-compatible IPv6 address
Global aggregatable addresses and link-local addresses are discussed in the next two sections, respectively. IPv4-compatible IPv6 addresses are described in the later "IPv4-to-IPv6 Transition Strategies and Deployments" section.
NOTE Site-local unicast addresses are another type of IPv6 unicast address; however, the use of site-local addresses was deprecated in September 2004 by RFC 3879, Deprecating Site Local Addresses, and future systems must not implement any support for this type of address. Site-local unicast addresses were similar to private addresses in IPv4 and were used to address a site without having a global prefix. Site-local addresses used the prefix FEC0::/10 (binary 1111 1110 11) with a subnet identifier (a 16-bit field) and an interface identifier (a 64-bit field) concatenated after the prefix. Site-local addresses were considered private addresses to be used to restrict communication to a limited domain.
IPv6 routers must not advertise routes or forward packets that have site-local source or destination addresses, outside the site.
KEY Every IPv6-enabled interface must contain at least one loopback (::1/128) and one linkPOINT local address. Optionally, an interface may have multiple unique local and global addresses.
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