Configuring IPv6 Addressing
It is easy to differentiate between IPv4 and IPv6 addresses. While IPv4 is an address of 32 bits and results in an address space of more than 4 billion, an IPv6 address utilizes 128 bits that results in an address space of 2128. Alternatively this can be represented as 340,282,366,920,938,463,463,374,607,431,768,211,456. This number also means that there are 54,525,952 addresses for every meter2 of earth.
IPv6 address permits multilevel subnetting and allocation of address between the internet backbone and subnets that exist in an organization. The address space increases allowing several unique IPv6 addresses being allotted to a network entity. Every address can be used for different purposes. The addresses that IPv6 provides are of two types - one that are equivalent to IPv4 address types and second that are unique to IPv6 and have a unique purpose.
IPv6 Address Syntax
A 128 bit IPv6 address is bifurcated into 16 bit blocks that are converted to a hexadecimal with four digits. Colons serve as separators and the system of representation is known by the nomenclature colon-hexadecimal. The Global unicast IPv6 addresses are the same as IPv4 public unicast addresses. Removal of the preceding zeros allows the address to be simplified in a block comprised of 16 bits though it is mandatory that every block have a digit. A contiguous sequence of 16-bit blocks that set to 0 in the colon-hexadecimal format can be compressed to ::.
IPv6 Address Prefixes
The prefix of the address indicates the bits with fixed values or bits that help identify the network. IPv6 prefixes are also represented using the slash as in the case of IPv4 address. Multinetting is a technique that allows assignment of multiple subnet IDs on the same link.
IPv6 Address Types
IPv6 addresses are of three types. They are discussed in detail in the following section.
- Unicast: This type of address is used for identifying a single interface that exists in the scope of unicast address type. Only a single interface receives a packets with a unicast address. IPv6 supports the following addresses (unicast) - Special, Global, Link-local, Site-local, Network Service Access Point (NSAP) and Internetwork Packet Exchange (IPX)addresses and Global unicast addresses.
- Multicast: Multiple interfaces can be identified using a multicast address. This type of address identifies multiple interfaces. All interfaces that are identified by the address receive the packets with a multicast address. A multicast address enables a packet to be sent to multiple hosts that are identified by the same address. The structure of the multicast address can be represented as:
Multicast address structure
- Anycast: These type of addresses identify multiple interfaces. All interfaces that are the nearest and identified by the address receive the packets with a anycast address. It is important that the routing infrastructure know the interfaces with anycast addresses and the distance with reference to routing metrics. Presently, these are used as destination addresses only and are assigned to routers alone.