Introduction to Subnetting
Subnetting allows a network administrator to create a smaller network known as sub-networks or subnets inside a large network by borrowing bits from the Host ID portion of the address. We can also make additional networks using those borrowed bits. It implements and manages a practical IP addressing plan by partitioning a single physical network into more than one smaller logical sub-network (subnets).
An IPv4 address contains a network portion and a host portion. Both portions of the IP address allow basic network groupings and help route packets between different networks. The router forwards packets based on the network portion of an IP address, and the host portion of the address allows for identification of the destination device. However, with the development of the network, many organizations are adding more hosts to their network, and the two-level hierarchy is not enough.
Further dividing a network adds another level to the network hierarchy. Division creates three levels: a network, a subnetwork, and a host. Subnetting also allows an organization to add sub-networks without needing a new network.
Subnetting is possible by borrowing bits from the IP address’s host portion. The borrowing bits assign a number of smaller subnetworks inside the original network. Subnets also decrease network traffic and cover network complexity. Subnetting is necessary when allocating a single network number, but more Local Area Network (LAN) is needed.
All IP addresses are divided into different classes and all the classes, such as Class A, B, and C include the subnet mask known as the default subnet mask. Using a subnet mask, we determine the class and number of IP addresses required for a given local network. The default subnet mask for each class is the following
- A: 255.0.0.0 or /8
- B: 255.255.0.0 or /16
- C: 255.255.255.0 or /24
We can partition a single Class A, B, or C network into smaller portions using subnetting. It is also possible to subnet a network repeatedly for more sub-networks. Subnetting a network into several subnets provides benefits as follows:
Subnetting Improve network performance and speed
A network is a logical broadcast domain in a computer network. Devices in the same network can reach each other by broadcast at the data link layer. A broadcast domain can be within the same network segment. A single broadcast packet sends information to reach every device configured into the same network or sub-network. An extensive network negatively impacts internetwork switching device performance and your network’s overall performance and speed.
Subnetting allows subnetworks to maximize their speed effectively. By dividing the network’s broadcast domains, the network administrator can better control traffic flow, thus increasing network performance. Subnetting also limits the number of devices on the subnet, which helps to control the traffic flow and network overhead.
Flexibility
It allows any organization to subnet its network according to how it is structured in its physical network. We can also modify the number of subnetworks and number of hosts per subnetwork for each organization, and they can decide on their own subnet structure and change it as required.
Routing Table size
The larger routing table size reduces the router’s efficiency, and the smaller routing table speeds up the entire routing process. We can minimize the size of the routing tables on the internet since additional networks that are not required will not be added to the table.
Simplified Management
Subnetting makes the job of a network administrator a lot easier. Using subnetting, an administrator can create logical host limits, as opposed to class full addresses. It makes host management very easy, and whenever an administrator wants to isolate some segments from others, he can easily do this job.
In classful addressing for more than 254 hosts or devices, we need a Class B network, which can waste thousands of IP addresses. We can select the number of bits by subnetting according to our host requirement. Subnetted networks are easier to manage and troubleshoot.
Reduce network congestion
We can reduce network congestion by strategically planning subnets, reducing the network’s load, and managing traffic efficiently.
Boost network security
Subnetting a large network into multiple networks allows us to isolate the compromised network. With the ability to isolate the compromised networks, we can easily prevent further damage to the network and resolve the problem easily.
