Complete Guide to Subnetting and Subnet Masks: Definition and Purpose

This is one of the calculations performed by someone who is engaged in the IT field. Ordinary people will be very foreign to hear this term. Subnetting is of course very important to build a network, for example networks in schools, companies, public places, and others. However, it is not only subnetting that is important in building a network. There are two things that certainly play an important role in a computer network, namely subnetting and subnet masks.

A subnet mask is a special technique for dividing or dividing a computer network into smaller subnetworks. This solving activity is called subnetting and can only be done on IP addresses consisting of classes A, B and C only. With the subnetting technique, a network can create several additional networks, but unfortunately this can reduce the maximum number of hosts in each network.

Subnetting is not done without a clear reason, but also has an important purpose. One of the goals is to efficiently allocate IP Address addresses in a computer network so that you can maximize the use of IP addresses. Next is to overcome the problem of differences in hardware and physical media used by a network, because IP routers can only integrate as a network with different physical media if each network has a unique network address and also to increase security on computer networks. Below is a further description of subnetting and subnet masks.

What Is Subnetting?

Subnets were originally designed to overcome the shortage of IP addresses over the Internet. This technique can break a network that is too large and complicated into smaller networks with new names that are easier to manage. This subnetting unfortunately cannot be used as long as it is. Subnetting is only suitable for certain classes of IP addresses. The notion of subnetting is a strategy used to separate a physical network into more than one smaller logical sub-network (subnet). The IP address includes both the network segment and the host segment.

Subnets are designed by receiving bits from the host portion of an IP address and using these bits to define a number of smaller subnets within the original network. The subnetting technique makes the network scale wider and not limited by the IP Classes A, B and C that have been set. With subnetting, we can create networks with more realistic host boundaries. Subnetting provides a more flexible way to determine which part of a 32-bit IP address represents the network ID and which part represents the host ID. With standard IP address classes, only 3 possible network IDs are available: 8 bits for class A, 16 bits for class B and 24 bits for class C.

What is a Subnet Mask?

Like the IP address, the subnet mask consists of four bytes (32 bits) and is written in the same notation as the IP address. Usually this is 255.255.255.0. For TCP/IP to work, you need a subnet mask. The subnet mask completes the IP address and by applying it to the IP address determines the subnet that the IP belongs to. The IP address has two components, the network address and the host address. Subnetting further divides the host portion of the IP address into subnets and host addresses if additional subnetworks are required. In effect, it masks the IP address and divides the IP address into a network address and a host address.

Subnetting function

One of the functions of subnetting is that it can help improve network performance and security. It’s time to consider subnetting your network. Although subnetting takes some planning and can be time consuming, it’s well worth the effort. Here are some of the benefits and functions of subnetting that you should consider.

1. Streamlining IP addresses

IP address saving allocates limited IP addresses to make it more efficient. If the internet were limited by addresses in class A, B, and C, each network would have 254, 65,000, or 16 million IP addresses for its host devices. Although there are many networks with more than 254 hosts, only a few networks (if not to say there are) have as many as 65,000 or 16 million hosts. And a network that has more than 254 devices will require a class B allocation and may waste around 10,000 IP addresses in vain.

2. Reduce network traffic

Subnetting ensures that traffic destined for devices in a subnet stays on that subnet, reducing lag. Through strategic subnet placement, you can help reduce network load and route traffic more efficiently.

So what happens to a large network without subnets? Each computer will see broadcast packets from all computers and servers on the network, so the switch must move all traffic to the appropriate port. This results in increased lag, reduced network performance, and slower response times. However, using routers to move traffic between subnets results without broadcast traffic or any information needing to be routed or moved to other subnets. As the amount of traffic within each subnet decreases, the speed of each subnet increases, which eases network congestion.

3. Improve network security

You may be thinking, “How are the devices on my network secure? By separating your network into subnets, you can control traffic flow using ACLs, QoS, or route maps, allowing you to identify threats, close points of entry and target your response more easily. You can also divide your network using routers to interconnect subnets through configuring ACLs on routers and switches. As a result, devices on the subnet cannot access the entire network. Another option is to limit access to resources on wireless clients, ensuring that valuable information is not easily accessible in remote locations.

4. Optimizing network performance and speed

Optimizing for network performance even if an organization has thousands of host devices, operating all these devices under the same network ID will slow down the network. The way TCP/IP works regulates that all computers with the same network ID must be on the same physical network as well. Physical networks have the same broadcast domain, which means a network medium must carry all traffic for the network. For performance reasons, networks are usually segmented into broadcast domains that are even smaller than Class C addresses.

Subnetting also divides your network’s broadcast domains, allowing you to better control traffic flow, thereby increasing network performance. A caveat, you are better off limiting traffic to a single subnet than letting it move from subnet to subnet.

Therefore, you should limit the number of devices on your subnet whenever possible, along with controlling the flow of traffic between subnets. Doing this will increase the speed and performance of your network.

Subnetting Purpose

In addition to the function there is also the purpose of this subnetting. The presence of this subnetting technique certainly makes it very easy for a network administrator to create and secure a network. As explained above, one of the benefits of subnetting is to increase network security. To find out what the purpose of subnetting is, the following is an explanation:

1. To make addressing efficient (for example for a network that only has 10 hosts, if we only use class C there are 254 – 10 = 244 unused addresses).
2. Dividing one network class over a number of subnetworks means dividing a network class into smaller parts.
3. Locating a host, whether on a network or not.
4. To overcome the problem of hardware differences with the physical network topology.
5. To make efficient allocation of IP addresses in a network in order to maximize the use of IP addresses.
6. Overcoming the problem of differences in hardware and physical media used in a network, because IP routers can only integrate various networks with different physical media if each network has a unique network address.
7. Improve security and reduce congestion due to too many hosts in a network.