Subnets
A subnet or subnetwork is a logical subdivision of an IP address network. The practice of dividing a network into two or more smaller networks is called subnetting. Subnets facilitate better control over network traffic and enhance security by isolating different parts of the network.
History and Development
Subnetting was first introduced with the deployment of Classless Inter-Domain Routing (CIDR) in the early 1990s. Before CIDR, networks were categorized into Classes A, B, and C, which were fixed in size. This led to inefficient use of IP address space. CIDR allowed for variable-length subnet masking (VLSM), enabling the division of networks into subnets of any size, thus improving address allocation efficiency.
How Subnets Work
- Subnet Mask: A subnet mask is used to determine the network portion of an IP address. It is a 32-bit number that masks an IP address, and when applied via a bitwise AND operation, it reveals the network address of an IP address.
- Subnetting: When a network is divided, each subnet gets its own network address, broadcast address, and a range of usable host addresses. The subnet mask defines how many bits are used for the network part and how many for the host part of the address.
- Benefits:
- Reduced network traffic by controlling broadcast domains.
- Improved network performance through segmentation.
- Enhanced security by isolating sensitive parts of the network.
- Better management of IP addresses.
- Subnetting Techniques:
Contextual Use
Subnets are crucial in:
- Local Area Networks (LANs): They help in segmenting large LANs into smaller, manageable networks.
- Virtual Private Networks (VPNs): Subnets are often used to define secure tunnels in VPNs.
- Cloud Computing: Cloud services often use subnets to manage network topology within virtual environments.
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