By far, the most significant aspect of IPv6 is its addressing capability. The address range of IPv4 is nearly depleted, and it is widely acknowledged that we are just at the beginning of the digital era. Therefore, we need an addressing scheme that offers more addresses than can possibly be used in the foreseeable future. IPv6 delivers exactly that. Whereas IPv4 uses a 32-bit address, IPv6 uses a 128-bit address that yields a staggering 340,282,366,920,938,463,463,374,607,431,768,211,456 possible addresses!
IPv6 addresses are expressed in a different format from those used in IPv4. An IPv6 address is composed of eight octet pairs expressed in hexadecimal, separated by colons. The following is an example of an IPv6 address:
42DE:7E55:63F2:21AA:CBD4:D773:CC21:554F
Subnetting
Now that you have looked at how IP addresses are used, you can learn the process of subnetting. Subnetting is a process by which the node portions of an IP address are used to create more networks than you would have if you used the default subnet mask.
To illustrate subnetting, let's use an example. Suppose that you have been assigned the Class B address 150.150.0.0. Using this address and the default subnet mask, you could have a single network (150.150) and use the rest of the address as node addresses. This would give you a large number of possible node addresses, which in reality is probably not very useful. With subnetting, you use bits from the node portion of the address to create more network addresses. This reduces the number of nodes per network, but chances are, you will still have more than enough.
There are two main reasons for subnetting. First, it allows you to use IP address ranges more effectively. Second, it provides increased security and manageability to IP networking by providing a mechanism to create multiple networks rather than having just one. Using multiple networks confines traffic to only the network that it needs to be on, which reduces overall network traffic levels. Multiple subnets also create more broadcast domains, which in turn reduces network wide broadcast traffic.
