Subnets

Subnets

What is a Network Subnet?

Subnet, which is short for sub-network, is a logical grouping of nodes, or devices, connected to a network (Mitchell). Subnetting can be defined as “the process of breaking down an IP network into smaller sub-networks called “subnets”” or the “process of segmentation of a network ID into multiple broadcast domains” (Subnetting). Subnets allow organizations to logically group their network devices. An organization may have subnets set up to create physical or geographical separations based on location, such as floor, building, city, or local area network (LAN) (Rouse, 2007) (Subnetting).

In this diagram, the network is divided into two subnets.

(What is a Subnet?, 2012)

Operation of the subnet is controlled in the network layer of the OSI model. The network layer decides the path data should take, taking into account the priority of service, network conditions and other factors (The OSI Model's Seven Layers Defined and Functions Explained). The network layer functions include functions such as routing, fragmentation and reassembly, and certain error handling and diagnostics (Kozierok, 2005).

The network layer is what gets separated into subnets. This allows management of the network and controlling the flow of data packets easier. To route traffic between networks, routers use the IP address, specifically the network or subnet portion of the address (Simoneau, 2006).

(Simoneau, 2006)

A broadcast domain is the smallest subnet where data can be transmitted directly from one device to another device. Communication between devices in a broadcast domain uses Media Access Control (MAC) addresses to communicate within the same small subnet. Communication using MAC addresses utilizes Address Resolution Protocol (ARP) broadcasting and does not occur between subnets (Ou, 2006).

Subnets share a common IP address with the network. Devices that have the same IP address prefix are part of the same subnet. The...