IP Address

Definition:
This is based on Internet Protocol Version 4. Internet Protocol Version 6 (IPv6) for a description of the newer 128-bit IP address.

An IP address is a 32-bit number that identifies each sender or receiver of information that is sent in packets across the Internet. When you request an HTML page or send e-mail, the Internet Protocol part of TCP/IP includes your IP address in the message (actually, in each of the packets if more than one is required) and sends it to the IP address that is obtained by looking up the domain name in the Uniform Resource Locator you requested or in the e-mail address you're sending a note to. At the other end, the recipient can see the IP address of the Web page requestor or the e-mail sender and can respond by sending another message using the IP address it received.

IP Address Classes and Their Formats:
Since networks are vary in size, there are four different address or classes to consider when applying to NIC for a network number:
Class A addresses - for large networks with many devices.
Class B addresses - for medium sized networks.
Class C addresses - for small networks (fewer than 256 devices).
Class D addresses - multicast addresses

IP Address Range:

Class A --- 1 -126 (00000001-01111110) 127.0.0.1 is a Loopback address.
Class B --- 128-191 (10000000-10111111)
Class C --- 192-223 (11000000-11011111)
Class D --- 224-239 (11100000-11101111)
Class E --- 240-255 (11110000-11111111)

Private IP Address:

Class A -- 10.0.0.0 to 10.255.255.255
Class B -- 172.16.0.0 to 172.31.255.255
Class C -- 192.168.0.0 to 192.168.255.255

Static and Dynamic IP:
Each device in an IP network is either assigned a permanent address (static IP) by the network administrator or is assigned a temporary address (dynamic IP) via DHCP software. Routers, firewalls and proxy servers use static addresses as do most servers and printers that serve multiple users. Client machines may use static or dynamic IP addresses. The IP address assigned to your service by your cable or DSL Internet provider is typically dynamic IP. In routers and operating systems, the default configuration for clients is dynamic IP.