Internet Protocol Address

Internet Protocol Addresses: An Internet Protocol Address, sometimes called an 'IP' Address or just an 'IP', is an address that is used to uniquely identify a computer connected to the Internet. IP Addresses come in two forms, v4 and v6 (version 4 and version 6, there is no version 5). Version 4 IP (or IPv4) addresses use four binary octets (32 bits) to represent a unique computer IP address. IPv4 addresses are usually written as four decimal numbers from 0 to 255 separated by dots. This is called 'dotted quad' notation. All Internet Protocol addresses are logical addresses which means they are stored in the computer's software configuration and can be changed when needed. When accessing a computer by name, the name is translated by a Domain Name Service server into an IP address. All Internet computers use IP addresses to identify the source and destination endpoints in their communication.

WHAT IS AN 'IP' or an 'IP address'?

An "IP" is an "Internet Protocol" address. IP addresses must be unique. All computers that use the Internet use only these unique IP addresses to talk to each other. Names such as http://www.yahoo.com are just for human convenience and are never used for computer communication. Computers use Domain Name Service (DNS) to turn the names humans understand into IP addresses computers understand. That is, they turn "www.yahoo.com" into "216.109.118.79". When you connect to Yahoo.com, your computer communicates with "216.109.118.79", not "www.yahoo.com".

An IP address is not part of the hardware of the computer. An IP address is something you can configure on the computer and is a unique address that is stored in the computer's software. This property of being unique makes it easy to find a specific computer using the IP address. The fact that the IP address does not come from the computer's hardware means that a computer can be replaced and the IP address it was using goes to the new computer instead of being thrown away with the old computer. This also allows you to change the address of the computer when you move the computer to another network. IP addresses are often referred to as logical addresses whereas MAC addresses are referred to as physical addresses.

What are IP addresses used for?

IP addresses are used to uniquely identify any device connected to a network running Internet Protocol. IP addresses are used when information is transmitted back and forth between computers. The transmitter is referred to as the source and the receiver is referred to as the the destination. Groups of all the addresses in a specific range are called networks or subnets.

Why do I need an IP Address?

You need an IP address to communicate with the Internet. If your computer is communicating with the Internet, you are using an IP address. Even if the computer you are sitting in front of does not have an IP address, there is a computer somehwere that does have an IP address and is using it to communicate with the Internet for you on your behalf.

If you are using a dial-up Internet Service Proivder (ISP) or an ISP using ISDN or a cable modem, you most definately have an IP address on your computer.

What does an IP address look like?

IP addresses use what is called a "dotted-decimal" or "dotted-quad" format. That means that the IP address is composed of four decimal numbers separated by periods (dots). These decimal numbers can range from 0 to 255. Each decimal number is represented using a single byte of computer memory (eight zeroes and ones). A single byte of computer memory can have any value from 0 - 255. Thus, an IP address is four bytes long.

DOTTED QUAD

216.236.128.9

What is my computer's IP address and how do I find out what it is?

YOUR INTERNET ADDRESS: [ 38.103.63.18 ].

You might not actually be directly connected to the Internet and the address shown above might not actually be your computer's IP address. You could be behind a firewall or proxy performing network address translation (NAT) or NAT with overload (Port Address Translation).

FINDING YOUR IP ADDRESS

Windows 98, 2000, ME and XP

Click on your start button and select MS-DOS or Command Prompt. Once a window opens, click in the window and type: ipconfig and press the enter key on your keyboard. Your results will look something like this:
       C:\Documents and Settings\username>ipconfig 
	   
	   Windows IP Configuration
	   
       Ethernet adapter Local Area Connection:
       Connection-specific DNS Suffix . : hostname.domain.com
            IP Address. . . . . . . . . . . . : 192.168.1.2
            Subnet Mask . . . . . . . . . . . : 255.255.255.0
            Default Gateway . . . . . . . . . : 192.168.1.1
       
MAC OS9 or earlier

Open the Apple Menu, select Control Panels and then select the TCP/IP (or MacTCP in Mac OS 7 or earlier) control panel. The IP Address will be displayed in the panel.

BSD / Unix/ Linux/ Mac OS X

Open a terminal window and type: ifconfig -a and press the enter key. If you have permission to run the ifconfig command, the output will look something like this:
% ifconfig -a
     wb0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
     inet6 fe80::202:3ff:ac06:2b4%wb0 prefixlen 64 scopeid 0x1
     inet 192.168.1.2 netmask 0xffffff00 broadcast 192.168.1.255
     ether 00:02:03:de:ca:fe
     media: Ethernet autoselect (100baseTX <full-duplex>)
     status: active
     plip0: flags=8810<POINTOPOINT,SIMPLEX,MULTICAST> mtu 1500
     lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> mtu 16384
     inet 127.0.0.1 netmask 0xff000000
     inet6 ::1 prefixlen 128
     inet6 fe80::1%lo0 prefixlen 64 scopeid 0x3

Summary

IP addresses uniquely identify individual computers attached to a network running Internet Protocol
IP addresses are written down as four numbers separated by dots (dotted-decimal notation).
Computers store IP addresses using four bytes. An IP address is four bytes.
IP addresses are controlled by a central authority (IANA) and assigned or allocated by the regional registries:
- ARIN - North America
- LACNIC - Latin America
- RIPE NCC - Europe
- APNIC - Asia/Pacific
- AFRINIC - Sub-Saharan Africa

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