IPv6 addresses are 128 bits long and the range of possible addresses can cater for about 340 sextillion network participants. IPv6 addresses consist of eight blocks of 16 bits and are written as hexadecimal numbers. The following is an example of a possible IPv6 address:
"2001:0db8:0000:0000:0000:54f3:dd6b:0001/64"
To improve the legibility of these IP addresses, zeros at the beginning of a block of numbers are omitted. It is also possible to omit one group of blocks that consist entirely of zeros. For the above example, one possible representation would be as follows:
"2001:db8::54f3:dd6b:1/64"
An IPv6 address consists of two parts; a prefix and an interface identifier. The prefix denotes the membership of the IP address to a network, while the interface identifier (e.g. in the case of auto-configuration) is generated from a link-layer address, and thus belongs to a particular network card. The device can also generate interface identifiers from random numbers. This improves security. In this way, multiple IPv6 addresses can be assigned to a single component.
The prefix describes the first part of the IP address. The length of the prefix is shown as a decimal number after a slash. For the example given here the prefix is:
"2001:db8::/64"
The remainder of the IP address is the interface identifier. In our example, this is:
"::54f3:ddb6:1"
Compared with the IP addresses for the IPv4 standard, a number of changes have resulted in the structure of the new IPv6 addresses:
- While IPv4 addresses cater for an address space of 32 bits, the new length of 128 bits results in a significantly larger address space with IPv6. IPv6 addresses are four times longer than IPv4 addresses.
- An interface can have multiple IPv6 addresses due to the potential assignment of multiple prefixes to a single interface identifier. With the IPv4 standard, an interface has only one IP address.
- The automatic assignment of IPv4 addresses always takes place via a DHCP server. However, IPv6 can operate an auto-configuration, which makes the use of a DHCP server unnecessary. However, the option of using a DHCP server is still open to you, as is the static configuration of the IP address.
