What is an IP address?

Q. What is an IP address? How do I get one?

A. An IP address ("Internet Protocol address") is a number that represents a single unique computer on the Internet. IP addresses are similar to telephone numbers, in that each computer (or telephone) must have its own unique IP address (telephone number.) Like telephones, there's a directory system - called the Domain Name System, or "DNS" - that can convert a name such as "www.apple.com" into a corresponding numeric IP address.

IP Addresses are written as a sequence of four numbers separated by ".", like this: 208.123.246.35. Each of the four numbers in the IP address can take the value between 0 and 255.

Every computer on the Internet must have a unique IP address. ISPs purchase large blocks of consecutive IP addresses, and then allocate smaller ranges of these addresses to their customers. Thus, a particular company might be assigned all the 254 IP addresses in the range 208.123.246.1 to 208.123.246.254. (The addresses ".0" and ".255" are not usually assigned.) Companies then assign the IP address to individual computers within the organization.