IPv6 addressing overview

IPv6 increases the number of network address bits from 32 (IPv4) to 128 bits, which provides more unique IP addresses to support increasing number of network devices.

An IPv6 address comprise 8 fields of 16-bit hexadecimal values separated by colons (:). The following figure shows the IPv6 address format.

Figure 10  IPv6 address format

As shown in the above figure, HHHH is a 16-bit hexadecimal value, while H is a 4-bit hexadecimal value. The following is an example of an IPv6 address.

2001:0000:0000:0200:002D:D0FF:FE48:4672

Note that this IPv6 address includes hexadecimal fields of zeros. To make the address manageable, you can:

  • Omit the leading zeros. For example, 2001:0:0:200:2D:D0FF:FE48:4672.
  • Compress the successive groups of zeros at the beginning, middle, or end of an IPv6 address to two colons (::) once per address. For example, 2001::200:2D:D0FF:FE48:4672.

When specifying an IPv6 address in a command syntax, consider the following:

  • You can use the two colons (::) only once in the address to represent the longest successive hexadecimal fields of zeros.
  • The hexadecimal letters in IPv6 addresses are not case-sensitive.

As shown in Figure 10, the IPv6 network prefix is composed of the left-most bits of the address. As with an IPv4 address, you can specify the IPv6 prefix using the prefix/prefix-length format, where the following applies.

The prefix parameter is specified as 16-bit hexadecimal values separated by a colon.

The prefix-length parameter is specified as a decimal value that indicates the network portion of the IPV6 address.

The following is an example of an IPv6 prefix.

2001:DB8:49EA:D088::/64

Parent topic: IPv6 Addressing