Introducing IPv6

IPv6 Addressing
The IPv6 addressing mechanism uses 128 bits to represent an IP address in a network and therefore, is capable of representing a vast amount of address spaces. The constituent bits of an IPv6 address are divided into eight groups and represented as 4-digit colon-hexadecimal notation.
E.g. 2001:0db8:3c4d:0015:0000:0000:abcd:ef12
Exploring IPv6
1.The IPv6 Shorthand Notation
2.The IPv6 Anatomy
3.The IPv6 Address Type
4.The IPv6 Unicast Addresses
5.The Advantages of IPv6 Addresses

The IPv6 Shorthand Notation
Most of IPv6 addresses contain multiple contiguous zeros that you can omit in an IPv6 address to simplify the given address.
E. g. 2011:0000:130F:0000:0000:09C0:876A:2012
2011:0:130F::09C0:876A:2012
You can not express like this
2011::130F::09C0:876A:2012
Another example
2011:0000:0000:0000:0000:0000:0000:2012
2011::2012

The IPv6 Anatomy
Although IPv6 addresses are longer than that of the IPv4 address, they are simpler to identify. Unlike the IPv4 addresses, the IPv6 addresses do not contain the variable number of bits for network and host ID’s, rather the IPv6 addresses are composed of two distinct components: the prefix/ network portion and host portion.
The prefix/network part: Allocates 64 bits of an IP address and represents either the bits with fixed values or the bits of the network part of the IP address. The prefix part is further divided into two portions: the 48-bit ISP portion and the 16-bit subnet
The host portion: Allocates 64 bits of an IP address and represents the host in a network

The IPv6 Address Types
The IPv6 addressing mechanism does not support the broadcast process of the host in a network. However, the IPv6 addresses can be used to send data packets to one or multiple hosts in the network simultaneously. Depending on the number of hosts top which data packets are sent, IPv6 address types.
Unicast: Identifies a unique interface that is the unique combination of network or subnet and network devices in a unicast address scope. In the unicast IPv6 address, the first 64 bits of the IP address represents the network components i. e. a network or subnet and rest 64 bits represents the host component. Numbers used to represent the network components are determined bi Internet Assigned Numbers Authority (AINA) and are distributed to ISPs.
Multicast: Identifies multiple interface or network devices in a group. It is similar to the IPv4 broadcast addresses. A data packet sent to multicast address is delivered to each interface of a group that is identified by the multicast address.
Anycast: Identifies multiple nodes in the network. In the case of anycast Ipv6 addressing, a single address is assigned to multiple nodes. When a data packet is sent to anycast address, it is delivered to the first available node. Consequently, it helps in load-balancing and automatic failover.

IPv6 Unicast Address
Link-local unicast address: Specifies that an IPv6 unicast address can only be used on the local network link and is not valid outside the enterprise network. This addresses are similar to IPv4 addresses that are configured through APIPA addresses and have an address format as FE80::/64. The Link-local addresses are assigned automatically assigned to the network device in a subnet and these devices communicate with other device with the help of link-local address.
The following illustration shows the structure of a link-local address.
Unicast unspecified address
The IPv6 unicast unspecified address is equivalent to the IPv4 unspecified address of 0.0.0.0. The IPv6 unspecified address is 0:0:0:0:0:0:0:0:, or a double colon (::).
Unicast loopback address
The IPv6 unicast loopback address is equivalent to the IPv4 loopback address, 127.0.0.1. The IPv6 loopback address is 0:0:0:0:0:0:0:1, or ::1

IPv6 Unicast Address
Site-local unicast address: Specifies that an IPv6 unicast address can only be used within the site of an organization. The IPv6 site-local unicast addresses are similar to the IPv4 private addresses. The prefix of used for IPv6 site-local unicast address is FEC0::/48, which implies that the IPv6 site-local unicast address always start with the prefix FEC0, followed by 32 zeros and 16-bit subnet identifier.
The following illustration shows the structure of a site-local address.
The initial 48 fixed bits are followed by a 16-bit Subnet ID field, which provides as many as 65,536 subnets in a flat subnet structure. Alternatively, you can subdivide the high-order bits of the Subnet ID field to create a hierarchical routing infrastructure. The last field is a 64-bit Interface ID field that identifies the interface of a node on a specific subnet.
Note
Global addresses and site-local addresses share the same structure after the first 48 bits — the 16-bit SLA ID of a global address and the 16-bit Subnet ID of a site-local address both identify the subnets of an organization’s site. Because of this, you can assign a specific subnet number to identify a subnet that is used for both global and site-local unicast addresses.