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| Lesson 5 | Subnets |
| Objective | Explain the purpose of subnetting and subnet masks. |
Subnet Masks:
This page explains the purpose of subnetting and subnet masks
by Thomas Hauck
What is subnetting?
There is a scarcity of network addresses today. A viable solution
to creating new network addresses is to divide the 32-bit address in a process called subnetting. The process entails modifying
the IP address by using the host (or client portion) address bits as network address bits. A more technical evaluation is that a
subnet mask is applied to filter the bits not used in the network address.
Subnetting is used when a company has more computers than can be connected to its network; it is also used as a traffic
reduction mechanism. However, all devices on the subnet must be programmed with the correct mask value in order for the network
to function properly.
Since subnetting tricks the IP Address by turning an unused portion of the Public Address into a Privated address (as discussed at the
end of Lesson 4). Subnetting can only occur within a LAN setting, and required a great deal of caution. An incorrect subnetting
scheme may violate IP addressing standards, which could cause the network address to be misinterpreted by Internet protocols.
This would result in widespread communications problems.
Subnet masks
To subnet an IP network, you use a subnet mask, which splits IP networks into subgroups of networks or subnetworks by filtering
unwanted bits so that only usable bits remain. Before using subnet masks, you must perform a decimal-to-binary conversion of the
IP address. A subnet mask identifies how the bits of an IP address are used. In binary terms, 0 and 1 are the only functional
digits. In binary notation, a 0 (zero) indicates that the bit is a host bit. A 1 (one) indicates that the bit is a network bit. A
subnet mask defines the network, the subnet, and the host.
The table below provides the default masks for IP address classes A to C.
The table below provides the default masks for IP address classes A to C.
In the next lesson, you will learn about remote access protocols.
