IP Address

IP Address

What is IP Address? 

• Internet Protocol Address (or IP Address) is an unique address that computing devices use to identify itself and communicate with other devices in the Internet Protocol network. 
• Any device connected to the IP network must have an unique IP address within its network.
•  An IP address is analogous to a street address or telephone number in that it is used to uniquely identify a network device to deliver mail message, or call ("view") a website.
• An IP address is a fascinating product of modern computer technology designed to allow one computer (or other digital device) to communicate with another via the Internet.
•  IP addresses allow the location of literally billions of digital devices that are connected to the Internet to be pinpointed and differentiated from other devices. 
• In the same sense that someone needs your mailing address to send you a letter, a remote computer needs your IP address to communicate with your computer.
• An Internet Protocol is a set of rules that govern Internet activity and facilitate completion of a variety of actions on the World Wide Web.
• Therefore an Internet Protocol address is part of the systematically laid out interconnected grid that governs online communication by identifying both initiating devices and various Internet destinations, thereby making two-way communication possible.
• An IP address consists of four numbers, each of which contains one to three digits, with a single dot (.) separating each number or set of digits. 
• Each of the four numbers can range from 0 to 255. Here's an example of what an IP address might look like: 78.125.0.209. 
• This innocuous-looking group of four numbers is the key that empowers you and me to send and retrieve data over our Internet connections, ensuring that our messages, as well as our requests for data and the data we've requested, will reach their correct Internet destinations. 
• Without this numeric protocol, sending and receiving data over the World Wide Web would be impossible.
• IP addresses can be either static or dynamic. 
• Static IP addresses never change. They serve as a permanent Internet address and provide a simple and reliable way for remote computers to contact you.
•  Static IP addresses reveal such information as the continent, country, region, and city in which a computer is located; the ISP (Internet Service Provider) that services that particular computer; and such technical information as the precise latitude and longitude of the country, as well as the locale, of the computer. 
• Many websites provide IP address look-up services to their visitors, free of charge. 

Dynamic IP addresses

• Dynamic IP addresses are temporary and are assigned each time a computer accesses the Internet. 
• They are, in effect, borrowed from a pool of IP addresses that are shared among various computers. 
• Since a limited number of static IP addresses are available, many ISPs reserve a portion of their assigned addresses for sharing among their subscribers in this way. 
• This lowers costs and allows them to service far more subscribers than they otherwise could.

Static IP addresses

• Static IP addresses are generally preferable for such uses as VOIP (Voice over Internet Protocol), online gaming, or any other purpose where users need to make it easy for other computers to locate and connect to them. 
• Easy access can also be facilitated when using a dynamic IP address through the use of a dynamic DNS service, which enables other computers to find you even though you may be using a temporary, one-time IP address.
•  This often entails an extra charge, however, so check with your ISP.
• Static IP addresses are considered somewhat less secure than dynamic IP addresses, since they are easier to track for data mining purposes. 
• However, following safe Internet practices can help mitigate this potential problem and keep your computer secure no matter what type of IP address you use.

Dotted Decimals

1. The traditional IP Addresses (IPv4) uses a 32-bit number to represent an IP address, and it defines both network and host address. 
2. Due to IPv4 addresses running out, a new version of the IP protocol (IPv6) has been invented to offer virtually limitless number of unique addresses. 
3. An IP address is written in "dotted decimal" notation, which is 4 sets of numbers separated by period each set representing 8-bit number ranging from (0-255). 
4. An example of IPv4 address is 216.3.128.12, which is the IP address assigned to topwebhosts.org.
5. An IPv4 address is divided into two parts: network and host address. 

Network address &  host address

The network address determines how many of the 32 bits are used for the network address, and remaining bits for the host address. 

The host address can further divided into subnetwork and host number.

Class A, B, C and CIDR networks

Traditionally IP network is classified as A, B or C network. The computers identified the class by the first 3 bits (A=000, B=100, C=110), while humans identify the class by first octet(8-bit) number. With scarcity of IP addresses, the class-based system has been replaced by Classless Inter-Domain Routing (CIDR) to more efficiently allocate IP addresses.

Class	Network Address	Number of Hosts	Netmask
CIDR	/4	240,435,456	240.0.0.0
CIDR	/5	134,217,728	248.0.0.0
CIDR	/6	67,108,864	252.0.0.0
CIDR	/7	33,554,432	254.0.0.0
A	/8 (1-126)	16,777,216	255.0.0.0
CIDR	/9	8,388,608	255.128.0.0
CIDR	/10	4,194,304	255.192.0.0
CIDR	/11	2,097,152	255.224.0.0
CIDR	/12	1,048,576	255.240.0.0
CIDR	/13	524,288	255.248.0.0
CIDR	/14	262,144	255.252.0.0
CIDR	/15	131,072	255.254.0.0
B	/16 (128-191)	65,534	255.255.0.0
CIDR	/17	32,768	255.255.128.0
CIDR	/18	16,384	255.255.192.0
CIDR	/19	8,192	255.255.224.0
CIDR	/20	4,096	255.255.240.0
CIDR	/21	2,048	255.255.248.0
CIDR	/22	1,024	255.255.252.0
CIDR	/23	512	255.255.254.0
C	/24 (192-223)	256	255.255.255.0
CIDR	/25	128	255.255.255.128
CIDR	/26	64	255.255.255.192
CIDR	/27	32	255.255.255.224
CIDR	/28	16	255.255.255.240
CIDR	/29	8	255.255.255.248
CIDR	/30	4	255.255.255.252

Note: (1) 127 Network Address reserved for loopback test. (2) Class D (224-247, Multicast) and Class E (248-255, Experimental) are not intended to be used in public operation. 

Public and Private IP Addresses 

In order to maintain uniqueness within global namespace, the IP addresses are publicly registered with the NetworkInformation Center (NIC) to avoid address conflicts. Devices that need to be publicly identified such as web or mail servers must have a globally unique IP address, and they are assigned a public IP address. Devices that do not require public access may be assigned a private IP address, and make it uniquely identifiable within one organization. For example, a network printer may be assigned a private IP address to prevent the world from printing from it. To allow organizations to freely assign private IP addresses, the NIC has reserved certain address blocks for private use. A private network is a network that uses RFC 1918 IP address space. The following IP blocks are reserved for private IP addresses.

Class	Starting IP Address	Ending IP Address
A	10.0.0.0	10.255.255.255
B	172.16.0.0	172.31.255.255
C	192.168.0.0	192.168.255.255

In addition to above classful private addresses, 169.254.0.0 through 169.254.255.255 addresses are reserved for Zeroconf (or APIPA, Automatic Private IP Addressing) to automatically create the usable IP network without configuration.

What is loopback IP address? 

1. The loopback IP address is the address used to access itself. The IPv4 designated 127.0.0.1 as the loopback address with the 255.0.0.0 subnet mask. 
2. A loopback interface is also known as a virtual IP, which does not associate with hardware interface. 
3. On Linux systems, the loopback interface is commonly called lo or lo0. The corresponding hostname for this interface is called localhost.
4. The loopback address is used to test network software without physically installing a Network Interface Card (NIC), and without having to physically connect the machine to a TCP/IP network. 
5. A good example of this is to access the web server running on itself by using http://127.0.0.1 or http://localhost.