IPv6 or Dynamic Host Configuration Protocol service provides network configuration for all connected hosts. It contains necessary information like gateway address for the network or the netmask. To effectively use available addresses, leases control the length of time of address usage.

IPv6

IPv6 is a stateless autoconfiguration, i.e., direct plug-and-play operation, described in detail in RFC 2462. No independent server or source required to connect to a network. The hardware network interfaces and routers directly determine the correct address. The IPv6 protocol includes configuration integrated into the Internet protocol directly to configure a host.

IPv6 Addressing

IPv6 is gradually replacing the older IPv4 version, although fully compatible with systems still using IPv4. It expands the number of possible IP addresses by using 128-bits, using eight 16-bit segments representing a unique hexadecimal number, each separated by a colon. The first 64 bits used for the network address and the host segment  or interface address expands to a 64-bit address allowing addressing for a far more significant number of systems. The interface ID is an Extended Unique Identifier (EUI-64) generated from a network device's Media Access Control (MAC) address. With the address space expansion, it also provides greater control over transmission at the address level.

An IP address also referred to as a host address. It supports 2 to the power 128 hosts, i.e., billion of a billion host. Supports stateless autoconfiguration of hosts, bypassing the need for DHCP to configure such addresses. Addresses generated directly using the MAC (Media Access Control) hardware interface of an interface.

Address Types

Addressing is controlled by the format prefix as the first field of the IP address. Three primary IPv6 addresses:

Unicast: used for a packet sent to a single destination. Three significant kinds of network addresses are global, link-local, and site-local, indicated by their format prefix.

  • Global addresses begin with the address type 3 and can be sent across the Internet. It uses four fields: the format prefix, global routing prefix, subnet identifier, and the interface identifier. The format prefix is 3 bits and the global routing prefix references the network address is 45 bits and the subnet ID references a subnet within the site is 16 bits.
  • site-local begins with format prefix FEC (10 bits), and then subnet identifier (54 bits) and the interface identifier (64 bits). It is used for hosts on a local network. They are only for local access and cannot be used to transmit over the Internet i.e., no network address.
  • link-local begins with format prefix FE8 (10 bits), followed by subnet identifier (54 bits) and the interface identifier (64 bits). It is used for physically connected systems on a small local network.

Multicast: used for a packet sent to more than one destination. It have format prefix of FF (8 bits) with flag and scope fields to indicate multicast group as permanent or temporary and whether local or global in scope.

Anycast: used to broadcast packet to a range of destinations

Loopback Address: 0:0:0:0:0:0:0:1
The sequence of zeros in adjacent fields represented by a shorthand symbol consists of double colon (::)
Loopback Address in Shorthand ::1

Kernel Configuration Support

Device Drivers -> Networking Support -> Networking Options -> The IPv6 Protocol

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