Hardware Reference
In-Depth Information
available with IPv4, but many of those numbers are ineligible for use as Internet addresses
because of the rules governing Internet addressing. For example, the entire block of
192.168.x.x
numbers is reserved for internal addressing on private networks.
Because the Internet has grown so large, we as a global community are running out
of available IP addresses. There are various translation systems in place that enable large
groups of computers on an internal network to share one or two IP addresses on the
Internet, but even those means aren't enough. Therefore
Internet Protocol version 6 (IPv6)
was invented, and it will at some point be implemented as the new means of identifying
computers on the Internet at large. IPv6 numbers are 128-bit binary numbers but are
written in hexadecimal to make them easier to comprehend. The number is broken into
four-digit sections separated by colons. (Hexadecimal is used instead of decimal so that
an IPv6 number is never confused with an IPv4 number, which uses decimal numbering.)
Here's an example:
4FFE:190C:4545:0003:0200:F8FF:FA21:67CF
With this large a number, the number of available addresses is virtually limitless. (Well,
not completely limitless. But 10 to the 36th power is a lot of addresses, and we'll probably
never use them up on planet Earth, even if every person alive has dozens of addresses.)
Static vs. Dynamic IP Addressing
When you set up a network connection on a PC, there are two ways to handle IP addressing.
One is to confi gure a
static IP address
on the device. Such an address is assigned by the
network administrator or your Internet service provider. Network administrators at large
companies spend a lot of time and energy developing complex systems of IP addressing, so
you should never guess at an IP address—always ask.
The other way is to allow a
Dynamic Host Confi guration Protocol (DHCP) server
to assign a
dynamic IP address
to a computer automatically. This is how large corporate
networks generally do it. They set up a server with DHCP, and every time a computer logs
on, the computer asks the DHCP server “What is my IP address?” The server assigns it one
immediately or reconfi rms that it's still okay to use the one it used last time. This system is
advantageous because it eliminates the possibility of duplicate IP addresses on a network
and saves the network administrator's time.
Automatic Private IP Addressing
Because a small peer-to-peer network doesn't have a DHCP server, small
networks need an alternative way of assigning IP addresses to its computers. You can
assign static IP addresses to computers if you like, but Windows networking is able to
pass out IP addresses automatically without a DHCP server via a system called
automatic
private IP addressing (APIPA).
Windows automatically assigns IP addresses within a
certain range of reserved addresses whenever it can't locate a DHCP server and no static
address has been supplied. The addresses in this reserved block begin with
169.254
, as in
169.254.2.1
.
