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.

IPv4 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, and thus can be expressed in 32 bits.

IPv6 addresses are expressed in 128 bits, allowing for a much larger address space than IPv4 addresses.

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.


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Last Modified On: February 27, 2019