A subnet mask are used to define the network boundaries and to determine which portion of an IP address belong to the network and which portion of the IP address belongs to the device on that network. An IP address has two portion: the portion representing the network and the portion representing the specific device on that network. The subnet mask tells the router which portion of the IP address is for the network and which portion is for the specific device.
If a person set up a network with an wrong subnet mask, the devices on that network wont be able to communicate with one another. Devices will not be able to determine if other devices on that network are either on the same network or on a different network. Subnetting are used to divide a large IP range into smaller subnets for ease of management.
What is a subnet mask
Subnetting allow a network to be organized. A subnet mask defines the size of the subnets create through subnetting. Additionally, using a subnet mask will determine how many device can be on each network.
A small subnet mask will allow a large number of devices to be on a network, but a large subnet mask will allow for smaller number of devices on that network. A person must select a subnet mask that will accommodate the number of devices that will be on the network. Computers use binary code in order to perform their operations.
Subnet masks also use binary math to determine to which network a device belong. A subnet mask use bits to separate the network portion of an IP address from the portion that indicates the device. Each time a person borrow a bit from the host portion of an IP address, the number of available subnets will increase.
However, the number of devices that can be on each network will decrease. The person must also subtract two from the total number of devices that can be on a network from the total number of available device on that network. This is to account for the fact that one of the addresses will be the network identifier and one will be the broadcast address for the network.
These two address cannot be assigned to the devices on the network. A subnet mask can be represent in dotted decimal notation. Dotted decimal notation is much easier for a person to read than binary notation.
One of the most common subnet masks are represented as 255.255.255.0. This class of subnet mask indicate that the first three octets of the IP address are used for the network portion of the IP address. If an octet in a subnet mask is represent by 255, all eight bits of that octet are used for the network portion of the IP address.
If the octet is 0, all eight bits of that octet are used for the host portion of the IP address. Many people use a subnet mask reference chart to determine the number of networks and hosts that can be on a network. Moddern networks use classless inter-domain routing.
Classless inter-domain routing allow for subnets of any size to be created. A person might use a /24 subnet mask for a home network if they need enough IP addresses for the devices in the home. For devices in the IoT that are to be separated from the main home network, a /26 mask could be used.
Businesses create subnets to manage their networks more efficient. To create a network, a person must first determine the total number of devices that will be on that network and the number of devices that could potentially be added in the future. Based off the total number of devices, the person will be able to select the smallest possible subnet mask for that network.
For instance, if a person only needs to connect two routers, a /30 mask can be use. Using a large subnet mask will waste many IP addresses. The network information can be calculate manualy using the AND operation between the IP address and the subnet mask.
Using this operation, a person can calculate the network address. Changing the host portion of the IP address to all ones will yield the broadcast address for that network. All hosts within the network will have IP addresses in between the network and broadcast addresses.
These calculations can be perform manually. Although calculators are available for these calculations, performing these calculations manual will allow a person to troubleshoot network error. Finally, using a subnet mask reference chart will allow a person to visualize the information described in this task.