(Tech) Network Addressing

  • Network Addressing is one of the major responsibilities of the network layer.
  • Network addresses are always logical, i.e., software-based addresses.
  • A host is also known as end system that has one link to the network. The boundary between the host and link is known as an interface. Therefore, the host can have only one interface.
  • A router is different from the host in that it has two or more links that connect to it. When a router forwards the datagram, then it forwards the packet to one of the links. The boundary between the router and link is known as an interface, and the router can have multiple interfaces, one for each of its links. Each interface is capable of sending and receiving the IP packets, so IP requires each interface to have an address.
  • Each IP address is 32 bits long, and they are represented in the form of “dot-decimal notation” where each byte is written in the decimal form, and they are separated by the period. An IP address would look like where 193 represents the decimal notation of first 8 bits of an address, 32 represents the decimal notation of second 8 bits of an address.

Let’s understand through a simple example


  • In the above figure, a router has three interfaces labeled as 1, 2 & 3 and each router interface contains its own IP address.
  • Each host contains its own interface and IP address.
  • All the interfaces attached to the LAN 1 is having an IP address in the form of 223.1.1.xxx, and the interfaces attached to the LAN 2 and LAN 3 have an IP address in the form of 223.1.2.xxx and 223.1.3.xxx respectively.
  • Each IP address consists of two parts. The first part (first three bytes in IP address) specifies the network and second part (last byte of an IP address) specifies the host in the network.

Classful Addressing

An IP address is 32-bit long. An IP address is divided into sub-classes:

  • Class A
  • Class B
  • Class C
  • Class D
  • Class E

An ip address is divided into two parts:

  • Network ID: It represents the number of networks.
  • Host ID: It represents the number of hosts.

In the above diagram, we observe that each class have a specific range of IP addresses. The class of IP address is used to determine the number of bits used in a class and number of networks and hosts available in the class.





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