Sunday, 15 April 2012

Basics of IP Address

Every machine connected to a network has a unique identifier. Computers use this unique identifier to send data to specific computers on a network. Most networks today, including all computers on the Internet, use the TCP/IP protocol as the standard for communication on the network. In the TCP/IP protocol, the unique identifier for a computer is called its IP address.
There are two standards for IP addresses: IP Version 4 (IPv4) and IP Version 6 (IPv6).


Most networks use IPv4 currently and they are slowly shifting to the new IPv6.
IPv4 uses 32bits to create a single unique address on the network. An IPv4 address is expressed by four numbers separated by dots. Each number is the decimal representation for an 8bit binary number, also called an octet.
Example: 192.168.10.15
IPv6 uses 128bits to create a single unique address on the network. An IPv6 address is expressed by eight groups of hexadecimal numbers separated by colons.
Example: 2001:cabd:0000:0000:0000:0000:2456:7481
Groups of numbers that contain all zeros can be replaced with an extra colon to mark the gap.
Example: 2001:cabd::2456:7481

Earlier when IPv4 started, internet was not as popular as today and was mostly private. But when internet expanded, the 2^32 addresses in IPv4 became insufficient. Hence the IPv6 system was introduced.

IP Classes
The entire IP address range is divided into several blocks each having special purpose.

0.0.0.0 - This represents the default network, which is the abstract concept of just being connected to a TCP/IP network.

255.255.255.255 - This address is reserved for network broadcasts, or messages that should go to all computers on the network.

127.0.0.1 - This is called the loop back address, meaning your computer's way of identifying itself, whether or not it has an assigned IP address.

169.254.0.1 to 169.254.255.254 - This is the Automatic Private IP Addressing (APIPA) range of addresses assigned automatically when a computer's unsuccessful getting an address from a DHCP server.

0.0.0.0 to 127.255.255.255 – Class A IP Address
128.0.0.0 to 191.255.255.255 – Class B IP Address
192.0.0.0 to 223.255.255.255 – Class C IP Address
224.0.0.0 to 239.255.255.255 – Class D IP Address
240.0.0.0 to 255.255.255.255 – Class E IP Address

Class A,B and C are the most commonly used IP in networks.

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