Routers do not forward datagrams
using link-local addresses, not even within the organization; they are
only for local communication on a particular physical network segment.
??” These addresses are used for link communications such as automatic
address con?¬?guration, neighbor discovery, and router discovery. Many
IPv6 routing protocols also use link-local addresses.
276 Chapter 7: Managing Address Spaces with NAT and IPv6
Loopback Address
Just as in IPv4, a provision has been made for a special loopback IPv6 address for testing;
datagrams sent to this address ???loop back??? to the sending device. However, IPv6 has just
one address, not a whole block, for this function. The loopback address is 0:0:0:0:0:0:0:1,
which is normally expressed using zero compression as ::1.
Unspecified Address
In IPv4, an IP address of all zeroes has a special meaning; it refers to the host itself and is
used when a device does not know its own address. In IPv6, this concept has been
formalized, and the all-zeroes address (0:0:0:0:0:0:0:0) is named the ???unspeci?¬?ed??? address.
It is typically used in the source ?¬?eld of a datagram that is sent by a device that seeks to
have its IP address con?¬?gured.
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