IPv4 subnetting is the process of dividing a single IP network into multiple smaller networks, known as subnets. This is done to improve network management, enhance security, and optimize the use of the limited IPv4 address space. Each subnet is identified by a subnet mask or netmask, which determines the network portion of the IP address.
An IPv4 address is a 32-bit number, typically represented in decimal format as four octets separated by dots (e.g., 192.168.1.20). The address is divided into two parts: the network portion and the host portion. The network portion identifies the specific network, while the host portion identifies a particular device within that network.
Subnetting involves borrowing bits from the host portion of an IP address to create a subnet part. This effectively increases the number of bits used to define the network, allowing for the creation of additional subnetworks within the original network. Subnet masks are used in conjunction with IP addresses to indicate which part of the address is the network portion and which is the host portion. The subnet mask consists of a series of 1s followed by a series of 0s; the 1s cover the network and subnet parts, while the 0s cover the host part.
Subnetting can be represented using CIDR (Classless Inter-Domain Routing) notation, which uses a slash followed by a number to indicate the number of bits in the network portion of the address (e.g., /24 for a subnet mask of 255.255.255.0).
The benefits of subnetting include improved network performance by reducing broadcast traffic within each subnet, enhanced security by isolating subnetworks, and more efficient IP address allocation to prevent wastage.
Subnetting is a fundamental concept in networking that allows for the logical segmentation of an IP network into smaller, more manageable parts, facilitating better control over traffic flow, security, and address allocation.