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Introduction to IPv6 Address
IPv6 addresses
An IPv6 address is represented as a series of 16-bit hexadecimals, separated by colons. An IPv6
address is divided into eight groups, 16 bits of each group are represented by four hexadecimal
numbers which are separated by colons, for example, 2001:0000:130F:0000:0000:09C0:876A:130B.
To simplify the representation of IPv6 addresses, zeros in IPv6 addresses can be handled as follows:
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Leading zeros in each group can be removed. For example, the above-mentioned address can be
represented in shorter format as 2001:0:130F:0:0:9C0:876A:130B.
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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.
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.
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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.
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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.
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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).
There are no broadcast addresses in IPv6. Their function is superseded by multicast addresses.