subnetwork

Subnetting is the process of dividing a network into two or more subnets. An IP address features numbers that identify the network ID and the host ID. A subnet address borrows some of the bits from the host ID of the IP address. Subnetting is largely invisible to computer users who aren't also network administrators. 

A subnetwork (subnet) is a separate and identifiable portion of an organization’s network, typically a local area network (LAN) comprised of all the machines on one floor, building or geographical location. Having several subnets allows an organization to be connected to the Internet with a shared network address, which means that all the machines on a given subnet have the same prefix to their IP addresses.

The practice of dividing a network into subnets is called subnetting.

A portion of a network that shares a common address component. On TCP/IP networks, subnets are defined as all devices whose IP addresses have the same prefix. For example, all devices with IP addresses that start with 100.100.100. would be part of the same subnet. Dividing a network into subnets is useful for both security and performance reasons. IP networks are divided using a subnet mask.

Advantages of Using Subnets:

• Improvements to network speed

• Reduced network congestion

• Efficiency gains for data delivery

• Improvements in network security

• Simplification of network administration

• Focused troubleshooting to just the subnet requiring support

• Barriers to data portability between subnets (e.g., departments or divisions of a company)

There aren't many disadvantages to subnetting. The process will likely require additional routers, switches, or hubs, which is an expense. Also, you'll need an experienced network administrator to manage the network and subnets.