Difference Between Subnetting and Supernetting | Computer Network

What is the main difference between Subnetting and Supernetting in Computer Networking?

Subnetting and supernetting is a very important topic in a computer network.

What is the role of Subnetting and Supernetting in Computer Network?

As computers are connecting all over the world through the internet, good monitoring over the network is required. This monitoring should be count in terms of proven security, ease in troubleshooting, performance improvement and reliable data transfer over the internet. This gives rise to subnetting and supernetting in the internet era.

First I will describe subnet and supernet. After that, I will talk about the difference between subnetting and supernetting.

What is Subnetting?

The process of dividing the single network into the multiple subnets is called as subnetting.

Suppose there an organization that has class A or class B block of the addresses assigned. An organization can divide these addresses into multiple contiguous groups. This individual group of addresses is called as a subnet.

You can read the detail of different IP address classes and their range. It will help you to understand this topic very well.

Advantages of Subnetting over Supernetting:

There are many advantages of using subnetting.

• It is difficult to maintain and administrate a big network with lots of systems connected. Dividing all these systems in multiple networks make easy to maintain and administrate for the network administrator.
• Restructuring of the networks becomes simple.
• As of dividing the network into multiple subnets, every subnet works independently. This improves the overall security of the network.
• In a case of any system failure, we don’t need to troubleshoot the complete network, rather subnet.

Disadvantages of Subnetting:

• If you are sending a data packet to any of the systems in the subnet, a packet has to be delivered to the particular network, then to subnet and then system. Every node (network, subnet, system) performs a filtering operation on the data packet. The operation for subnet filtering gives extra overhead.
• It complicates the communication process.
• To identify each subnet in a network, we need to assign an id for each subnet. Some extra bits are borrowed from IP address for the subnet id. So we lose some IP addresses.

What is Supernetting?

The process of aggregating two or more networks for which it generates a single IP address is called as supernetting.

It is considered as the reverse process of subnetting.

Why is suppernetting required?

Let’s take an example.

Class C block provides 256 host addresses. 
Class B block provides 65536 host IP addresses.

If any of the organization wants 500 IP addresses, 
class C block will not be sufficient. 

Having 65536 addresses in class B block 
is a waste of IP addresses.

To tackle with this, an organization can apply for 
two contiguous class C block of IP addresses and combine both of them.

The combined network is called as supernet and the process of aggregation is called as supernetting.

Limitation of supernetting over subnetting:

• All the networks in the supernet must be using the same IP address class.
• As it is an aggregating process, it does not make sense to apply on a single network.

Difference Between Subnetting and Supernetting:

Every 32 bit IP address has network and host identifier bits. Network identifier bits decide which network data packet should be sent. Host identifier bits determine the host inside the network to deliver the packet.

Refer the following IP address classes diagram with host and network identifiers bits.

Subnetting:

• Subnetting is a process of dividing network for ease of monitoring.
• The number of 1’s in the subnet mask is always greater than or equal to the number of network identifier bits.
• For the subnet mask, bits are borrowed from the host identifier bits.
• The subnet mask is applicable to a single network.

Supernetting:

• Supernetting is a process of aggregating multiple networks into a single network.
• The number of 1’s in the supernet mask is always less than the number of network identifier bits.
• For a supernet mask, bits are borrowed from the network identifier bits.
• The Supernet mask is applicable for two or more networks. These networks should be of the same IP address class.

IP Subnetting Online Calculator

These are the very important point you should know. You can see lots of questions in various placement interviews and to find the difference between subnetting and supernetting.

If you are looking for a reference book to prepare for computer networking, I would like to recommend you a Computer Networks by Tanenbaum book. No other book can beat this one if you want to extract knowledge from this gold mine. Go for it!

Computer networking is my favorite topic. It is really so interesting. If you have any point to discuss over subnetting vs supernetting, feel free to write in the comment section below.  I will try to reply you as soon as possible.

Aniruddha Chaudhari

I am a Python enthusiast who loves Linux and Vim. I hold a Master of Computer Science degree from NIT Trichy and have 10 years of experience in the IT industry, focusing on the Software Development Lifecycle from Requirements Gathering, Design, Development to Deployment. I have worked at IBM, Ericsson, and NetApp, and I share my knowledge on CSEstack.org.