What is IP Address Subnets? Subnet Using Binary Method Explained

By | 9th November 2015

Connectivity between hosts on an IP network is determined by the application of network and destination address. This is done by the communicating host comparing and applying its subnet mask to both its IPv4 address and to the destination IPv4 address.

Remember, the subnet mask is a 32 bit value which is used to differentiate between the network bits and the host bits of the IP address. The subnet mask is made up of a string of 1s followed by a string of 0s.

The 1s indicate the network bits and the 0s specify the host bits within the IP address. The network bits are matched between the source and destination. If networks are the same, the packet can then be delivered locally. If they don’t match, the packet is sent to the default gateway.

For example, let’s assume PC 1, with the IP address of 192.168.1.40  and subnet mask of 255.255.255.0,  needs to send a message to PC 2, with the IP address of 192.168.1.52 and a subnet mask of 255.255.255.0. In this case, both hosts have a same default subnet mask of 255.255.255.0. Both hosts have the same network bits of 192.168.1, and therefore are on the same network.




How to Calculate Subnets Using Binary Method

PC 1 sends a message to PC 2. The switch checks to see if PC 2 is on the same network as PC 1. The network is determined by comparing the IP address to the Subnet Mask. Let’s look at The IP Address, Subnet Mask, and Network Address for each configuration in binary equivalent below:

PC 1 Configuration 

IP Address – 192.168.1.40, 11000000.10101000.00000001.00101000 

Subnet Mask – 255.255.255.0, 11111111.11111111.11111111.00000000 

Network – 192.168.1.0, 11000000.10101000.00000001.00000000 

PC 2 Configuration 

IP Address – 192.168.1.52, 11000000.10101000.000000001.00110100 

Subnet Mask – 255.255.255.0, 11111111.11111111.11111111.00000000 

Network 192.168.1.0, 11000000.10101000.00000001.00000000 




The highlighted area above shows that both PC 1 and PC 2 are on the same network: 192.168.1.0.

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