H3C Technologies H3C S5560 Series Switches - Manual (Page 155)

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IMPORTANT:
A double colon can appear once or not at all in an IPv6 address. This limit allows the device to
determine how many zeros the double colon represents and correctly convert it to zeros to restore a
128-bit IPv6 address.
An IPv6 address consists of an address prefix and an interface ID, which are equivalent to the network
ID and the host ID of an IPv4 address.
An IPv6 address prefix is written in IPv6-address/prefix-length notation. The prefix-length is a decimal
number indicating how many leftmost bits of the IPv6 address are in the address prefix.
IPv6 address types
IPv6 addresses include the following types:
• Unicast address—An identifier for a single interface, similar to an IPv4 unicast address. A packet
sent to a unicast address is delivered to the interface identified by that address.
• Multicast address—An identifier for a set of interfaces (typically belonging to different nodes),
similar to an IPv4 multicast address. A packet sent to a multicast address is delivered to all
interfaces identified by that address.
There are no broadcast addresses in IPv6. Their function is replaced by multicast addresses.
• Anycast address—An identifier for a set of interfaces (typically belonging to different nodes). A
packet sent to an anycast address is delivered to the nearest interface among the interfaces
identified by that address. The nearest interface is chosen according to the routing protocol'
measure of distance.
The type of an IPv6 address is designated by the first several bits, called the format prefix.
Table 6 Mappings between address types and format prefixes
Type Format prefix (binary) IPv6 prefix ID
Unicast
address
Unspecified address 00...0 (128 bits) ::/128
Loopback address 00...1 (128 bits) ::1/128
Link-local address 1111111010 FE80::/10
Global unicast address Other forms N/A
Multicast address 11111111 FF00::/8
Anycast address
Anycast addresses use the unicast address space and have the
identical structure of unicast addresses.
Unicast addresses
Unicast addresses include global unicast addresses, link-local unicast addresses, the loopback address,
and the unspecified address.
• Global unicast addresses—Equivalent to public IPv4 addresses, global unicast addresses are
provided for Internet service providers. This type of address allows for prefix aggregation to restrict
the number of global routing entries.
• Link-local addresses—Used for communication among link-local nodes for neighbor discovery and
stateless autoconfiguration. Packets with link-local source or destination addresses are not
forwarded to other links.