Subnet Basics and Subnet Masks

Study Notes

A subnet is a smaller network within a larger network, created by dividing an IP address into two parts: network ID and host ID.
Subnets are used to organize and structure a network, making it easier to manage and improve communication between devices.

A subnet mask is a 32-bit number that determines the scope of a subnet.
It is used to differentiate between the network ID and host ID in an IP address.
The subnet mask is applied to the IP address using a bitwise AND operation.

Fixed-Length Subnet Mask (FLSM): uses a fixed subnet mask for all subnets.
Variable-Length Subnet Mask (VLSM): uses a different subnet mask for each subnet, allowing for more efficient use of IP addresses.

Determine the number of subnets needed: based on the number of devices and networks required.
Determine the number of bits to borrow: from the host ID to create the subnet mask.
Create the subnet mask: by setting the borrowed bits to 1.
Divide the network into subnets: using the subnet mask to create the subnets.

Subnet address: the network address of a subnet, calculated by performing a bitwise AND operation on the IP address and subnet mask.
Broadcast address: the highest address in a subnet, calculated by performing a bitwise OR operation on the IP address and the complement of the subnet mask.
Number of hosts per subnet: calculated by subtracting the number of subnets from the total number of hosts.

Improved network organization: subnets make it easier to manage and maintain a network.
Increased security: subnets can be used to isolate sensitive areas of the network.
Better use of IP addresses: subnetting allows for more efficient use of IP addresses.

A subnet is a smaller network within a larger network, created by dividing an IP address into two parts: network ID and host ID, allowing for better organization and structure of a network.

A subnet mask is a 32-bit number that determines the scope of a subnet, allowing devices to differentiate between the network ID and host ID in an IP address.
The subnet mask is applied to the IP address using a bitwise AND operation, creating a boundary between the network ID and host ID.

Fixed-Length Subnet Mask (FLSM): uses a fixed subnet mask for all subnets, simplifying network design and management.
Variable-Length Subnet Mask (VLSM): uses a different subnet mask for each subnet, allowing for more efficient use of IP addresses and accommodating networks of varying sizes.

Determine the number of subnets needed based on the number of devices and networks required, ensuring efficient use of IP addresses.
Determine the number of bits to borrow from the host ID to create the subnet mask, depending on the number of subnets needed.
Create the subnet mask by setting the borrowed bits to 1, establishing a clear boundary between the network ID and host ID.
Divide the network into subnets using the subnet mask, creating separate networks for better organization and management.

The subnet address is the network address of a subnet, calculated by performing a bitwise AND operation on the IP address and subnet mask.
The broadcast address is the highest address in a subnet, calculated by performing a bitwise OR operation on the IP address and the complement of the subnet mask.
The number of hosts per subnet is calculated by subtracting the number of subnets from the total number of hosts, ensuring accurate network planning.

Subnetting improves network organization, making it easier to manage and maintain a network by dividing it into smaller, more manageable sections.
Subnetting increases security by allowing for the isolation of sensitive areas of the network, reducing the risk of unauthorized access.
Subnetting enables better use of IP addresses, reducing waste and ensuring that IP addresses are allocated efficiently, even in large networks.