What is Subnetting ?

Subnetting is the practice of dividing a network into two or more smaller networks. It increases routing efficiency, and enhances the security of the network. I also reduces the size of the broadcast domain.

Example of Subnetting


In the picture above we have one huge network: All hosts on the network are in the same subnet, which has the following disadvantages:

  • a single broadcast domain – all hosts are in the same broadcast domain. A broadcast when sent by any device on the network here- all hosts process the broadcast. This also creates lots of unnecessary traffic.
  • network security – each device can reach any other device on the network, which can present security problems. For example, a server containing sensitive information shouldn’t be in the same network as user’s workstations.
  • organizational problems – in a large networks, different departments are usually on group of different subnets. For example, you can group all devices from the Accounting department in the same subnet and then give access to sensitive financial data only to hosts from that subnet.

Subnetting of the network above can happen like this: :

subnetting, subnet

Now, when we create two subnets for different departments: for Accounting and for Marketing. Devices in each subnet here will be in a different broadcast domain. This will reduce the amount of traffic flowing on the network and allow us to implement packet filtering on the router.

In case you have any queries related to subnetting, please feel free to mention those in the comments sections.

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