Subnetting Explained  with an Example

Subnetting is the concept of dividing bigger network IP address space into smaller independent address groups.  Each group has a separate network id. Subnetting creates two or more separate broadcast network. Which reduces network load and provides more security to the network users.

Subnetting example:

For example, if a LAN connects to the internet using a router. The computers on LAN are of C  class of IP address. The LAN can have a maximum of 254 hosts with same Network Id. If a LAN computer has an IP address 192.168.1.*.  The network id is 192.168.1. The subnet mask is 24 bits and value is 192.168.1 or we can say The total number of network ids possible are oxFFFFFF in case of C class IP address. Which a huge number. Subnetting gives an opportunity of dividing the broad range into smaller ones.  In our example, the subnet mask is Means, when the router needs to send an IP packet to any computer on the LAN, the value of network address in the destination ip is compared against the 192.168.1, if matches packet is sent to the LAN else not.

With the subnetting, we can create two (or more) LANs with the different network masks. One LAN may have subnet mask*/24, and other LAN have 192.168.2.*/24

Subnetting Advantages:

Based on subnetting, we can divide the communication computers into groups. Division brings many advantages for the network and LAN users.

Logical separation:  In the company, there can be multiple (one HR other is operations) departments. Each has its servers and other things on the LAN machines. Is there is no subnetting, each one can access any computer over LAN. With subnetting, only the computers in a subnet address can be accessed.  Separation brings more security to the department-specific data. 

Reduces Broadcast packets: After subnetting a packet is sent to the computers those network id matches with the subnet.  For example, if there are six computers over LAN with to subnet. Each subnet has three computers with subnet mask od and respectively when an incoming packet comes into the LAN, the router broadcast packet to only three machines.  Because the network packet can only belong to a subnet, but before subnetting, all six devices get the broadcast.


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