Variable Length Subnet Masking (VLSM) is a technique used to allocate IP addresses to subnets of different sizes. It involves dividing an IP address range into smaller subnets of varying sizes to make more efficient use of IP addresses. This technique is particularly useful for larger networks that need to conserve IP addresses while also allowing for flexibility and scalability.
In this article, we will explore VLSM in more detail, including its benefits, how to use it, and common terms associated with VLSM.
What is VLSM?
Variable Length Subnet Masking (VLSM) is a method used to allocate IP addresses to subnets of different sizes. It allows network administrators to divide an IP address range into smaller subnets of varying sizes, depending on the specific needs of the network. This is in contrast to traditional subnetting, which involves dividing a network into equal-sized subnets.
Benefits of VLSM:
The primary benefit of VLSM is that it allows network administrators to make more efficient use of IP addresses. By dividing an IP address range into smaller subnets of varying sizes, it is possible to allocate IP addresses more precisely, reducing the number of unused IP addresses.
Another benefit of VLSM is that it allows for flexibility and scalability. Network administrators can adjust the size of subnets as needed to accommodate changes in the network, such as the addition of new hosts or the creation of new subnets.
How to use VLSM:
Using VLSM involves the following steps:
For example, suppose you need to allocate IP addresses to a network with the following requirements:
100 hosts for subnet A
50 hosts for subnet B
25 hosts for subnet C
To use VLSM to allocate IP addresses to these subnets, you would follow these steps:
Convert the number of hosts required for each subnet into binary form:
Subnet A: 100 hosts = 01100100
Subnet B: 50 hosts = 00110010
Subnet C: 25 hosts = 00011001
Determine the number of bits required to accommodate each binary value:
Subnet A: 7 bits
Subnet B: 6 bits
Subnet C: 5 bits
Add the number of bits determined in step 2 to the original subnet mask to create a new subnet mask:
Subnet A: 255.255.255.128 (original mask) + 7 bits = 255.255.255.254 (new mask)
Subnet B: 255.255.255.128 (original mask) + 6 bits = 255.255.255.192 (new mask)
Subnet C: 255.255.255.128 (original mask) + 5 bits = 255.255.255.224 (new mask)
Divide the network into subnets using the new subnet masks:
Subnet A: 192.168.1.0/25
Subnet B: 192.168.1.128/26
Subnet C: 192.168.1.192/27
Common terms associated with VLSM:
Benefits of VLSM
VLSM offers several benefits, including:
Efficient use of IP address space: VLSM allows network administrators to divide an IP address space into smaller subnets, which reduces the number of IP addresses wasted on unused subnets.
Flexibility: VLSM provides flexibility in the allocation of IP addresses, allowing administrators to create subnets of various sizes.
Scalability: VLSM allows for the creation of subnets of different sizes, making it easier to scale a network as it grows.
Improved network performance: By creating smaller subnets, VLSM reduces the size of broadcast domains, which can improve network performance.
In conclusion, VLSM is a powerful technique that allows network administrators to divide an IP address space into subnets of variable sizes. VLSM offers several benefits, including efficient use of IP address space, flexibility, scalability, and improved network performance. By using VLSM, network administrators can optimize their network and improve its overall efficiency.