1. What is VLSM Subnetting?

VLSM (Variable Length Subnet Mask) allows you to divide an IP network into subnets of different sizes, making more efficient use of IP address space compared to traditional fixed-length subnetting.

2. How Does the Calculator Work?

The calculator uses the following process:

Where:

• \( base\_net \) — The base IP network (e.g., 192.168.0.0/24)
• \( mask\_lengths \) — List of subnet mask lengths (e.g., 26,27,28)

Explanation: The calculator divides the base network into subnets according to the specified mask lengths, allocating the largest subnets first.

3. Importance of VLSM

Details: VLSM is crucial for efficient IP address allocation, especially in networks with segments of different sizes. It helps minimize IP address wastage.

4. Using the Calculator

Tips: Enter the base network in CIDR notation (e.g., 192.168.0.0/24) and comma-separated list of subnet mask lengths (e.g., 26,27,28). The calculator will allocate subnets from largest to smallest.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between VLSM and FLSM?
A: FLSM (Fixed Length Subnet Mask) uses the same subnet size throughout, while VLSM allows different sizes for different subnets.

Q2: When should I use VLSM?
A: Use VLSM when your network has segments with significantly different host requirements (e.g., WAN links vs. user segments).

Q3: What's the proper order for VLSM allocation?
A: Always allocate the largest subnets first, then progressively smaller ones to avoid fragmentation.

Q4: Can any network use VLSM?
A: Yes, but it requires careful planning and routing protocols that support VLSM (like OSPF or EIGRP).

Q5: How does VLSM help with IP conservation?
A: By matching subnet sizes exactly to segment needs, VLSM prevents wasting IP addresses on unnecessarily large subnets.