Understanding IPv

Although IPv4 allows for more than four billion networked computers and devices, the world is running out of available IPv4 addresses. Rather than allow there to be a shortage of available addresses, organizations have worked together to create several solutions to the problem. One of these solutions is IPv6. Unlike IPv4, which uses 32-bit addresses, IPv6 uses 128-bit addresses, which offer literally enough IP addresses so that there are thousands of IP addresses for each square yard of the Earth's surface. Or put another way, there are about 340,282,367,000,000,000,000,000,000,000,000,000,000 available addresses—give or take a few hundred million quadrillion.

To make it easier to track all those IP addresses, IPv6 uses hexadecimal numbers rather than decimal numbers to define the address space. This means that instead of allowing only the numbers 0 through 9 for each position in the IP address, IPv6 allows the values 0 through 9 and A through F, with A representing 10, B representing 11, and so on, up to F representing 15. Thus, the values 0 through 15 can be represented using the values 0 through F.

IPv6's 128-bit addresses are divided into eight 16-bit blocks delimited by colons. With standard IPv6 addresses, the first 64 bits represent the network ID and the last 64 bits represent the network interface being used. Since many IPv6 address blocks are set to 0, a contiguous set of 0 blocks can be expressed as ::, a notation referred to as the double-colon notation. Table 14-6 shows an example of an IPv6 IP address and an abbreviated IP address.

Table 14-6. IPv6 address example

IPv6 address

Abbreviated IPv6 address



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