Subnetting is the process of dividing a larger network into smaller subnetworks or subnets. This is done by borrowing bits from the host portion of the IP address to create a subnet mask, which determines the range of IP addresses available for hosts in each subnet.
In this article, we will provide a step-by-step guide to help you understand IP subnetting.
Step 1: Determine the IP Address Class
The first step in subnetting is to determine the IP address class. IP addresses are divided into 5 classes: A, B, C, D, and E. Classes A, B, and C are commonly used for networking.
Class A networks have a default subnet mask of 255.0.0.0, Class B networks have a default subnet mask of 255.255.0.0, and Class C networks have a default subnet mask of 255.255.255.0.
Step 2: Determine the Number of Subnets Needed
The next step is to determine the number of subnets needed. This is based on the number of departments, locations, or other factors that require separate networks. To determine the number of subnets, you need to borrow bits from the host portion of the IP address.
For example, if you need 4 subnets, you need to borrow 2 bits (2^2 = 4) from the host portion of the IP address.
Step 3: Determine the Number of Hosts Needed per Subnet
The next step is to determine the number of hosts needed per subnet. This is based on the number of devices that need to be connected to the network in each subnet.
To determine the number of hosts per subnet, you need to subtract 2 from the total number of IP addresses in the subnet. The first IP address is used for the network address, and the last IP address is used for the broadcast address.
For example, if you need 100 hosts per subnet, you need to have a subnet that provides at least 102 IP addresses (100 + 2).
Step 4: Create the Subnet Mask
The subnet mask determines the range of IP addresses available for hosts in each subnet. To create the subnet mask, you need to determine the value of the bits you borrowed from the host portion of the IP address.
For example, if you borrowed 2 bits from the host portion of the IP address, you need to determine the binary value of those bits. In this case, the binary value would be 11 (2 bits).
The subnet mask for this example would be 255.255.255.192 (or /26 in CIDR notation). This subnet mask provides 64 IP addresses (2^6 = 64) per subnet.
Step 5: Determine the Valid Host Range
The valid host range is the range of IP addresses available for hosts in each subnet. To determine the valid host range, you need to subtract 2 from the total number of IP addresses in the subnet.
For example, if you have a subnet with a subnet mask of 255.255.255.192, the total number of IP addresses in the subnet is 64. Subtracting 2 gives you 62, which is the number of valid IP addresses in the subnet.
The first IP address in the subnet is used for the network address, and the last IP address is used for the broadcast address. Therefore, the valid host range for this example would be 192.168.1.1 – 192.168.1.62.
Conclusion
Subnetting is an important tool that allows you to optimize your network performance and improve security. By dividing a larger network into smaller subnets, you can reduce network congestion, increase efficiency, and create separate segments for different departments or functions within your organization.
Follow another step by step walkthrough here – https://www.expertnetworkconsultant.com/subnetting/step-by-step-guide-to-understanding-ip-subnetting/