Also known as a netmask, a subnet mask is a 32-bit decimal based number which is used for determining which part of the IP address is used for the host, and which part is used by network.

If you were look look at an IP address by itself, there really isn’t a concise way to read it. That’s where the subnet mask comes in. The subnet mask “masks out” the network part of the address, and gives you more information on the IP address. This operation is mandatory for communications on the IP network.

Ex.) 192.168.1.33 + 255.255.255.0 = 192.168.1.0   This means that a computer with an IP of 192.168.1.33 belongs to a subnet named 192.168.1.0.

When looking at the default classes for subnets, they are as follows:

• Class A = 255.0.0.0
• Class B = 255.255.0.0
• Class C = 255.255.255.0

The “255″ is the network prefix, and the “0″ is the host suffix.

How to check you current subnet mask

Its quite easy to do using a bulit-in Windows utility called “ipconfig”. Just follow these easy steps:

On the task bar, click Start -> Run
When the prompt comes up to type a command, type in “cmd” (minus the quotes)
This will bring up your command prompt.
Once the prompt is up and ready to go, type in “ipconfig”
You will then see your IP address, default gateway, and subnet mask displayed on screen!
(It most likely is currently set to 255.255.255.0)

How to change your subnet mask

• First, goto Start -> Control Panel
• While in Classic view, double-click on Network Connections
• Right-click on your Local Area Connection or main internet connection, and click properties.
• Go down and select the Internet Protocol (TCP/IP) and click properties
• Place a mark in the ticker that says “Use the following IP address”
• Here you will need to configure a new IP and default gateway, but you will also be able to change the subnet mask to anything you’d like.
• After you’ve done this, you may check to see if the changes have set in place by using ipconfig. (Just follow the steps listed above).

If you are interested in how the subnet mask works, you can tinker around with a tool called the IP Subnet Calculator found here. It’s a really good tool for calculating the subnet info using various things such as: “… network class, IP address, subnet mask, subnet bits, mask bits, maximum required IP subnets and maximum required hosts per subnet.” They also have other great tools such as the CIDR Calculator that you may want to check out.

Related posts:

1. How to find Subnet Mask If you want to find your subnet mask of the...
2. DHCP Scope DHCP stands for Dynamic Host Configuration Protocol; it’s used to...
3. How to Change IP Address Often we have the need to change out IP address...
4. Subnetting Creation of two or more sub-sections that are visible logically...
5. How to change MAC Address Most of the people think MAC address can not be...