Also, the network ID of S1 is 201.10.1.0. The Network ID of the whole network is 201.10.1.0. So, because of subnetting, there is a loss in the number of IP addresses. Overall, there are 252 usable hosts after subnetting. So, there are actually 126 usable hosts in the second subnet. But, the first IP address (201.10.1.128)is the network ID of the first subnet and the last IP address(201.10.1.255) is the Direct Broadcast Address of the first subnet. Similarly, in the 2nd subnet network(S2), we have a total of 128 hosts. So, there are actually 126 usable hosts in the first subnet. But, the first IP address (201.10.1.0)is the network ID of the first subnet and the last IP address(201.10.1.127) is the Direct Broadcast Address of the first subnet. In 1st subnet network(S1), we have a total of 128 hosts. The range of IP address that lies in the 2nd subnet network is from 201.10.1.128 to 201.10.1.255. The range of IP address which is in 1st subnet network is from 201.10.1.0 to 201.10.1.127. If we want to divide it into four subnet networks then we need 2 bits(2ВІ=4 networks). Using one bit we can divide it into 2 networks i.e. If the leftmost bit of the host address is 0 then it is the 1st subnet network and if the leftmost bit is 1 then it would be 2nd subnet network.

We are going to borrow the left-most bit of the host ID and declare for identifying the subnet. A class C network has 24 bits for Network ID and the last 8 bits for the Host ID. So, in subnetting we will divide these 254 hosts logically into two networks.

This is because the first IP address is for the network ID and the last IP address is Direct Broadcast Address(for sending any packet from one network to all other hosts of another network ). So the total number of hosts is 256(for class C host is defined by last octet i.e. Suppose we have a class C network having network ID as 201.10.1.0( range of class C 192вЂ“223). So if we divide this large network into the smaller network then maintaining each network would be easy.

So to manage such a large number of hosts is a tedious job. SubnettingДividing the network into smaller networks or subnets is called subnetting. Subnet(SubNetwork)ДЄ subnet is a logical partition of an IP network into smaller networks. You should know about what are the various classes of IP and how it is divided before reading this blog. In this blog, we will start from the basics and see how this is done by the router. The subnet mask helps the router in doing so. Given an IP address, how will the router identify what is the network ID of the network to which this IP address belongs? The router has a routing table for this.

Subnet mask table