It has become a standard that computer systems communicate with each other through IP (internet protocol). This guide discusses only the currently widespread used IPv4 (internet protocol version 4). IPv4 is facing a shortage of addresses so that your ISP would try various means and ways to save public IP addresses.

There are various modes of IP networks. Among them are,

• the world wide web public network usually called "the Internet",
• and your home/office private internet network is normally called a "local area network" (LAN).

Note that the imprecise term "the Internet" conveniently used by almost everyone, including the internet gurus, actually means "the public world wide internet network". Internet is actually the protocol, be it a private internet network or the public internet network.

Since a LAN is private, you can assign any address you want as long as no two computers on a LAN have the same address. For a computer to operate on the public Internet, it must have a public IP address conforming to the world wide internet authority.

Therefore, for a LAN computer to connect to the world wide internet, it needs to go through a router with NAT (network address translation).

You need to remember to differentiate between two modes of IP addresses

• public IP address dispensed by your ISP for your modem conforming to world wide internet addressing
• private IP addresses dispensed by your router or modem for use within your LAN.

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