What is a Subnet?
In computer networking, a subnet is a subset of a larger network that has been divided into smaller, more manageable parts. This division is done to help reduce network congestion and improve overall network performance.
To understand subnetting, it is essential to understand the concept of IP addresses. An IP (Internet Protocol) address is a unique identifier assigned to each device connected to a network. This identifier is used to route data packets between devices on the network. IP addresses consist of a network ID and a host ID.
For example, consider the IP address 192.168.1.1. In this IP address, 192.168.1 is the network ID, and 1 is the host ID. The network ID identifies the network to which the device belongs, and the host ID identifies the specific device on that network.
Subnetting allows us to divide the network ID portion of an IP address into smaller subnetworks, each with its own network ID and range of host IDs. This division allows network administrators to allocate network resources more efficiently, reduce network congestion, and enhance network security.
How Subnetting Works:
Subnetting works by taking a portion of the host ID bits and using them to create a new network ID. The number of bits used for the network ID determines the number of subnets that can be created. The remaining bits are used for the host ID.
For example, let's say we have the IP address 192.168.1.1 with a subnet mask of 255.255.255.0. The subnet mask determines which portion of the IP address represents the network ID and which portion represents the host ID.
In this case, the subnet mask 255.255.255.0 means that the first three octets (192.168.1) represent the network ID, and the last octet (1) represents the host ID. This means that we have a maximum of 254 hosts on this network (2^8 - 2 = 254, where 2^8 is the total number of possible host IDs for the last octet, and we subtract 2 because the first and last host IDs are reserved).
To create a subnet, we can borrow some of the bits from the host ID and use them to create a new network ID. For example, if we borrow one bit from the host ID, we can create two subnets, each with its own network ID and range of host IDs.
To do this, we change the subnet mask to 255.255.255.128, which means that we are using seven bits for the network ID and one bit for the host ID. This gives us two subnets with a range of 0-127 and 128-255 for the host IDs. The new network IDs are 192.168.1.0 and 192.168.1.128.
We can continue to borrow bits from the host ID to create more subnets. For example, if we borrow two bits, we can create four subnets with a range of 0-63, 64-127, 128-191, and 192-255 for the host IDs.
The new subnet mask for this would be 255.255.255.192, which means we are using six bits for the network ID and two bits for the host ID. The new network IDs are 192.168.1.0, 192.168.1.64, 192.168.1.128, and 192.168.1.192.
We can continue this process to create even more subnets with smaller ranges of host IDs. The number of subnets and hosts per subnet that can be created depends on the number of bits that are borrowed