There's actually a third important category:  private addressing.

  Technically, that breaks the "every computer has a unique address"
condition.  Computers using a private address need to be on a private
network behind a gateway with a public address, which implements translation
between the public and private address spaces.  So the same private
addresses may be in use behind multiple public gateways.

David Gillett



On 27 Jan 2005 at 8:53, Sven wrote:

> Hello Chilangisha,
>
> For "us" computer users on the end of the line, the IP Address is assigned
> by our ISP. The ISP itself has a 'block' of IP addresses assigned to it.
> Beyond the local ISP, the system gets more complicated and can be confusing.
> You may ask, "If the ISP only has a fixed number of addresses to use, how do
> they manage it?" The answer is there are two forms of IP addresses, static
> and dynamic.
>
> Static IP addressees never change. This means you have to the same IP
> address each and every time you log onto the Internet. However, there are
> only a finite number of IP addresses in the world. Once the maximum number
> of IP addresses an ISP has access to is used up, they no longer can issue
> static IP addresses to customers. Static IP addresses have become a coveted
> thing these days. If it is available from your ISP they probably charge an
> additional fee for it.
>
> This is where the dynamic IP address comes into play. Basically, dynamic IP
> addresses are pooled. With dynamic IP addresses, when you need to log onto
> the Internet, you connect to your ISP and they assign you an IP address. As
> soon as you log off the Internet, your IP address goes back into the pool
> for the next customer to use.
>
> Here are links for more reading on IP addresses:
>
> Howstuffworks "What is an IP address?":
> http://computer.howstuffworks.com/question549.htm
>
> What is IP address? - A Word Definition From the Webopedia Computer
> Dictionary:
> http://www.webopedia.com/TERM/I/IP_address.html
>
> Webopedia: Understanding IP Addressing:
> http://www.webopedia.com/DidYouKnow/Internet/2002/IPaddressing.asp
>
> Sven Swanson, Sr.
>
> ----- Original Message -----
> From: "Chilangisha B Changwe" <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Friday, January 27, 2006 12:43 PM
> Subject: [PCBUILD] Ip addresses
>
>
> I am new to networking and I have a question on IP addressing. I know
> there are 3 classes of IP addresses; A, B, and C. My question is who
> assigns these addresses so that every computer has a unique address?
>
> Chilangisha Changwe

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