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What is an IPv6 Address

The greatest benefit of IPv6 addressing over the previous used IPv4 addressing is the enormous addressing space that contains.

IPv6 supports 128 bit addressing space and can potentially support 2 ^ 128 or 3.4 x 10 ^ 38 unique IP addresses (as opposed to 32 bit addressing space of IPv4). With this enormous addressing space scheme, IPv6 can provide unique addresses to each and every device attached to the Internet.


IPv6 addresses are classified into three categories:

1) Unicast addresses: A Unicast address acts as an identifier for a single interface. An IPv6 packet sent to a Unicast address is delivered to the interface identified by that address.

2) Multicast addresses: A Multicast address acts as an identifier for a group/set of interfaces that may belong to the different nodes. An IPv6 packet delivered to a Multicast address is delivered to the multiple interfaces.

3) Anycast addresses: Anycast addresses act as identifiers for a set of interfaces that may belong to the different nodes. An IPv6 packet destined for an Anycast address is delivered to one of the interfaces identified by the address.


IPv6 addresses are denoted by eight groups of hexadecimal quartets separated by colons in between them.

Following is an example of a valid IPv6 address: 2002:cdba:0000:0000:0000:0000:3257:9652

Any four-digit group of zeroes within an IPv6 address may be reduced to a single zero or altogether omitted. Therefore, the following IPv6 addresses are similar and equally valid:

The URL for the above address will be of the form:



The IPv6 networks are denoted by Classless Inter Domain Routing (CIDR) notation. A network or subnet using the IPv6 protocol is denoted as a contiguous group of IPv6 addresses whose size must be a power of two. The initial bits of an IPv6 address (these are identical for all hosts in a network) form the networks prefix. The size of bits in a network prefix are separated with a “/”.

For example, 2001:cdba:9abc:5678::/64 denotes the network address 2001:cdba:9abc:5678. This network comprises of addresses rearranging from 2001:cdba:9abc:5678:: up to 2001:cdba:9abc:5678:ffff:ffff:ffff:ffff. In a similar fashion, a single host may be denoted as a network with a 128-bit prefix. In this way, IPv6 allows a network to comprise of a single host and above.

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