The A to Z of Internet Protocol (IP)

The Internet Protocol features five classes of address, namely class A, class B, class C, class D and class E addresses. Each of these classes exists as a subset of the IPv4 range of addresses with a contiguous subset of addresses.

Numbering Method of the IP Addressing System

IPv4 address classes have a start address and an end address, defining a range for that class. The ranges for IPv4 address classes are as follows:

  • Class A – 0.0.0.0 to 127.255.255.255 with 0xxx as leftmost bits
  • Class B – 128.0.0.0. to 191.255.255.255 with 10xx as leftmost bits
  • Class C – 192.0.0.0 to 223.255.255.255 with 110x as leftmost bits
  • Class D – 224.0.0.0 to 239.255.255.255 with 1110x as leftmost bits
  • Class E – 240.0.0.0 to 254.255.255.255 with 1111 as leftmost bits

As indicated above, the leftmost bits in an IP address indicate its class. As an example, consider Class D addresses with the following binary representation:

110xxxxx xxxxxxxx xxxxxxxx xxxxxxxx

Here, the address has 32 bits, with its leftmost bits set to 110. The other 29 bits can take either a 1 or 0 in place of the x.

internet protocol ip

All addresses falling in the range between 192.0.0.0 and 223.255.255.255 represent the above binary address internally.

Multicast and Limited Broadcast Addresses of the IPv4 Family

Class D and Class E are special classes of IP addresses. Class D addresses are multicast addresses. Multicasting refers to the process of sending messages to only a restricted group of clients on a Local Area Network (LAN). On the other hand, unicasting is the process of sending messages to a single node on the LAN. A Local Area Network that employs multicasting primarily belongs to research networks and is not intended for use with ordinary nodes on the Internet.

On the other hand, Class E addresses are ‘Reserved’ addresses, and not used on any of the IP networks. Even when a device tries to use this address, it will be unable to communicate over the Internet. Some research organizations, however, use Class E addresses for experimental purposes.

A Limited Broadcast Address is indicated by the IP address 255.255.255.255. Limited Broadcast Addresses deliver messages to many different recipients. To send a message to all clients on a LAN, and not the Internet publicly, you must direct it to 255.255.255.255.

The range of addresses between 255.0.0.0 and 255.255.255.255 are reserved addresses for broadcast purposes. These addresses do not belong to the Class E range of addresses.

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