An IP address (with IP for Internet Protocol) is the number that identifies each computer connected to the Internet, or more generally and specifically, the network interface of any computer hardware (router, printer) connected to a computer network using the Internet Protocol. There are IP version 4 and version 6. In 2007, version 4 is the most used; it's usually denoted with four numbers between 0 and 255, separated by dots; Example: 126.96.36.199. Determination and Use of Addresses in an IP Network
In version 4 of the protocol, the IP address is usually automatically transmitted and assigned to start using the Dynamic Host Configuration Protocol (DHCP). Otherwise, it's also possible to fix a computer IP address in the configuration of its operating system. The autoconfiguration mechanisms also exist. In version 6, the principle of autoconfiguration is strengthened.Each data transmitted by the Internet protocol is tagged with two IP addresses to identify the sender and recipient. The network uses the destination address to transmit the data. The recipient knows who responds with the IP address of the sender. Each component connected to the network must have at least one IP address to establish connections. More Technically
In each frame sent using the IP protocol, the header specifies the pair (IP destination address, IP address of the sender) to enable the routing protocol to route the frame properly. The destination machine will know the origin of the information it receives, so to respond if needed.One or more IP addresses can be assigned to a host. This assignment can be done either manually (including IPv4) or automatically via an appropriate protocol (such as DHCP or RARP or IPv6).The IP address is used mainly to route data to the destination network where the machine is located. Then, in the case of IPv4, the ARP table is the last gateway that's sought to convert the address IP into a MAC address. The IP Address and Domain Name
Most IP addresses can be converted into a domain name and vice versa. The domain name is more readable to humans: fr.wikipedia.org is the domain corresponding to 188.8.131.52. This is the name resolution system. Subnet Masks
The subnet mask shows which portion of an IP address matches the network number and which part is the host number portion.The principles are the same IP version 4 and version 6. However, the practice is not the same. CIDR notation is used systematically.A mask has the same length as an IP address. It consists of a sequence of digits ending with 1 (if applicable) or the numerals 0:1 2 30 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1+ - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - +| 1 1 1 1 1 1 1 1 | 1 1 1 1 1 1 1 1 | 1 1 1 1 1 1 1 1 | 1 0 0 0 0 0 0 0 |+ - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - +255.255.255.128 maskTo calculate the subnet part of an IP address, it perform a logical operation on each bit of the address and mask. To calculate the host address, it performs a bitwise operation between the complement of the mask and address.In other words, just keep the bits in there, where the address mask bits are 1 (a number of bits from the left of the address). Part B number is contained in bits that remain (rightmost). Principle CIDR
The Classless Inter-Domain Routing, CIDR for short, was developed to (mainly) to decrease the size of the routing table contained in routers. This object is achieved by aggregating a number of entries in this table into one. Thanks and I hope this was helpful.