About IP Address
Published: Saturday, April 3, 2004
What is an IP address?
IP stands for Internet Protocol, the most popular open-system protocol used to communicate accross any sets of interconnected networks including Local Area Networks (LAN) or Wide Area Networks (WAN). An IP address is an identification number assigned to a device (e.g. a computer or a printer) in such a network. Other devices in the network or out of that network uses this IP address to connect to this device via communication protocols such as Transmission Control Protocol (TCP) or Internet Protocol (IP).
An IP address consists of 4 sets of 8-bit numbers (octet) with a total of 32-bits, each separated by a dot (.). For each of the 4 sets of octets in an IP address, the maximum possible value is 255 (representing an octet containing all ones). Therefore, the values of IP addresses can range from 0.0.0.0 to 255.255.255.255, which translates to 3,720,314,628 different IP addresses.
Example of an IP address in decimal and binary -
Within a private network, any valid IP address can be assigned to the devices as long as they are kept unique from one another within that network. However, assigning of IP addresses for server and devices connected to the internet is governed by organizations such as ARIN (United States), RIPE NCC (Europe) and APNIC (Asia Pacific), so that no duplicate IP addresses are assigned.
Classification of IP addresses
An IP address consists of two portions - one identifies the network and the other identifies the device or the node within that network. For example, in case of the IP address 220.127.116.11, the network is identified by 123, whereas the node is identified by 45.67.89. The rules of breaking down an IP address into network and nodes is decided by the classification. Though the decimal representation of IP address is easier for human usage, computers use the binary representation and the classification of the IP address is also based on the binary numbers.
- Class A: This class of IP addresses start with a binary number 0 (decimal numbers from 0 to 127). The network is identified by the first octet (the first set of the IP address). For example, the IP address 18.104.22.168 belongs to class A because the first set of numbers is 123 (between 0 and 127). The network ID is 123, whereas the node ID is 45.67.89.
The IP address 127.0.0.1 is a special IP reserved for internal loopback testing. For example, if someone connects to a local host (same computer running the server), the IP address is 127.0.0.1. It does not create any network traffic. Also the IP address 0.0.0.0 represents a default fallback value and not assigned to any network. Therefore, class A can support 126 network addresses, each containing 16 million nodes.
- Class B: The binary number starts with 10 (decimal numbers from 128 to 191). The network is identified by the first two octets (the first two sets of the IP address). For example, the IP address 22.214.171.124 belongs to class B, because the first set of numbers is 178 (between 128 and 191). The network ID is 178.95, whereas the node ID is 234.23. Class B can support 16,000 network addresses, each containing 65,000 nodes.
- Class C: The binary number starts with 110 (decimal numbers from 192 to 223). The network is identified by the first three octets (the first three sets of the IP address). For example, the IP address 126.96.36.199 belongs to class C, because the first set of numbers is 210 (between 192 and 223). The network ID is 210.223.99, whereas the node ID is 145.
Class B can support more than 2 million network addresses, each containing 254 nodes.
- Class D: The binary digits start with 1110 (decimal numbers from 224 to 239). This class of IPs are reserved for multicast purposes.
- Class E: The E class of IP addresses start with binary digits 1111 (ranging from 240 to 255 in decimal format). This class of IP addresses are reserved for testing purposes and not assigned for public usage.