3Com 4210 PWR Configuration Manual page 529

Leading zeros in each group can be removed. For example, the
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above-mentioned address can be represented in shorter format as
2001:0:130F:0:0:9C0:876A:130B.
If an IPv6 address contains two or more consecutive groups of zeros, they can
■
be replaced by the double-colon :: option. For example, the above-mentioned
address can be represented in the shortest format as
2001:0:130F::9C0:876A:130B.
c
CAUTION: The double-colon :: can be used only once in an IPv6 address.
Otherwise, the device is unable to determine how many zeros the double-colon
represents when converting it to zeros to restore the IPv6 address to a 128-bit
address.
An IPv6 address consists of two parts: address prefix and interface ID. The address
prefix and the interface ID are respectively equivalent to the network ID and the
host ID in an IPv4 address.
An IPv6 address prefix is written in IPv6-address/prefix-length notation, where
IPv6-address is an IPv6 address in any of the notations and prefix-length is a
decimal number indicating how many bits from the left of an IPv6 address are the
address prefix.
IPv6 address classification
IPv6 addresses mainly fall into three types: unicast address, multicast address and
anycast address.
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.
Anycast address: An identifier for a set of interfaces (typically belonging to
■
different nodes).A packet sent to an anycast address is delivered to one of the
interfaces identified by that address (the nearest one, according to the routing
protocols' measure of distance).
n
There 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 Their function is superseded by multicast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 383 lists the
mapping between major address types and format prefixes.
Table 383 Mapping between address types and format prefixes
Type
Unicast Unassigned address
address
Loopback address
Link-local address
Site-local address
Global unicast address other forms
Multicast address
Format prefix (binary)
00...0 (128 bits)
00...1 (128 bits)
1111111010
1111111011
11111111
IPv6 Overview 527
IPv6 prefix ID
::/128
::1/128
FE80::/10
FEC0::/10
-
FF00::/8