What is IPv6

The IETF identified the problem with the rapid exhaustion of the IPv4 address space several decades ago. Despite the invention of classless IP addressing, it was assessed that a new addressing protocol was required to address long term needs. IPv6 was then designed as the succeeding standard to IPv4 and released in 1995. The resulting address space was then increased from 32 to 128 bits (16 octets) and deemed to be adequate for at least the mid-term requirements for Internet growth. The design of IPv6 incorporates the idea of allowing efficient aggregation of subnet routing prefix at the router level. This results in the reduction of routing table sizes and actual address utilization rates being small on any IPv6 network segment. The design also allows for the separation of the addressing infrastructure of a local segment’s space from the addressing used to route to or from external network traffic. The large number of network addresses also allows large blocks to be assigned for a specific purpose and when required aggregated for more efficient routing. The need for more complicated addressing conservation methods such as now used in Classless Inter-Domain Routing (CIDR) is also eliminated with the implementation of IPv6.
Similar to IPv4, IPv6 reserves blocks of IP address for private use. In IPv6; however, these are referred to as unique local addresses (ULA). This block of addresses uses the routing prefix fc00::/7 that is then divided into two /8 blocks that have different implied policies. The addresses include a 40-bit pseudorandom number which minimizes the risk of address collisions if packets are routed inappropriately or sites merge. None of the current or legacy IPv6 private address prefixes are supposed to be routed on the public Internet just like the behavior expected from IPv5. Finally, despite the majority of modern operating systems now providing support for IPv6, it has not yet seen widespread deployment in the home networking, VoIP, and networking peripheral fields.