5 Subnetting Benefits

Learn how subnetting can help improve network performance and security.

CBT Nuggets

January 31, 2017

4 Min Read
Network Computing logo

Uh oh, traffic on your network has increased tremendously, causing it to run slower. It’s time to consider subnetting your network. While subnetting takes some planning and can be time consuming, it’s well worth the effort. Here are five subnetting benefits you should consider

1. Improve network performance and speed

A single broadcast packet sends out information that reaches every device connected to that network because each device has an entry point into the network. A large number of entry points, however, can negatively impact internetwork switching device performance, as well as your network’s overall performance.

Another issue with broadcast packets is that they can spam every device within a network, even devices that aren’t relevant to the task at hand, which can strain a network’s capacity and cause it to collapse.

But subnetting enables you to ensure that information remains in the subnetted network or broadcast domain, which allows other subnets to maximize their speed and effectiveness. Subnetting also divides your network’s broadcast domains, enabling you to better control traffic flow, thus increasing network performance!

A word of caution, though. You’re better off limiting traffic to a single subnet instead of letting it move from subnet to subnet. So, you should limit the number of devices on your subnet whenever possible, along with controlling the traffic flow between subnets. Doing this will improve your network’s speed and performance.

2. Reduce network congestion

Subnetting ensures that traffic destined for a device within a subnet stays in that subnet, which reduces congestion. Through strategic placement of subnets, you can help reduce your network’s load and more efficiently route traffic. 

So, what happens to a large network with no subnets? Every computer would see broadcast packets from all the computers and servers on the network, resulting in the switches having to move all that traffic to the appropriate ports. This leads to increased congestion, reduced network performance, and slower response times.

However, using a router to move traffic between subnets results in no broadcast traffic or any information that doesn’t need to be routed being moved to other subnets. Because the amount of traffic within each subnet is reduced, the speed of each subnet is increased, which eases network congestion.

3. Boost network security

You might be thinking, “What if a device in my network is comprised?” By splitting your network into subnets, you can control the flow of traffic using ACLs, QoS, or route-maps, enabling you to identify threats, close points of entry, and target your responses more easily.

You also can split your network using routers to connect subnets though the configuration of ACLs on the routers and switches. As a result, devices in a subnet are unable to access the entire network.

Another option is to limit access to resources on wireless clients, ensuring that valuable information isn’t easily accessible in remote locations.

4. Control network growth

When you're planning and designing a network, size is something that needs to be taken into consideration. One of the key benefits of subnetting is that it enables you to control the growth of your network.

You can use a popular host formula to determine the size of your network. Take the number of zeros in the mask of your subnet when converted to binary, take two to the power of that number, then minus two — and then you will have the number of possible hosts for that subnet mask. That was a bit of a doozy, so here’s a more in-depth explanation of the host formula.

Your next step is to figure out the expected growth of the network, which in most cases will be based heavily on the physical size of your building. For example, will the number of devices needed remain steady or could it eventually double? If so, you will need to adjust the equation for the host formula accordingly, in order to determine the proper IP address space for your network.

5. Ease administration

Are you a network admin? Then subnetting is a no-brainer because it can make your job a lot easier. By subnetting, you can create networks that have more logical host limits, as opposed to the limitations of IP addressing classes: Eight bits for Class A, 16 bits for Class B, and 24 bits for Class C. Think about it this way, if the internet was limited to only those three classes, every network would have only 254, 64,000, or 16 million IP addresses for host devices.

In the absence of subnets, networks with more than 254 devices need a Class B allocation, which can waste thousands of IP addresses. By subnetting, you can select the number of bits in your subnetwork, creating more realistic host limits.

Subnetting also is an effective way to keep tabs on the machines on your network, which in turn can help you determine which machines need attention should problems arise. So while they take careful planning and implementation, subnetted networks generally are easier to manage and troubleshoot.

Learn more about subnetting in this video with Keith Barker, a CBT Nuggets trainer.

About the Author(s)

CBT Nuggets

Established in 1999, CBT Nuggets provides high-quality, on-demand online IT training videos for IT professionals on technologies including networking, virtualization and cloud computing – from independent experts and leading vendors such as Cisco, Microsoft and Google. The Eugene, Oregon-based company features trainers who are widely-respected and sought out in the IT industry. Visit us at CBTNuggets.com.

Stay informed! Sign up to get expert advice and insight delivered direct to your inbox

You May Also Like

More Insights