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Learn subnetting

VLSM Fundamentals

Learn how variable-length subnet masking allocates different subnet sizes from one parent network.

Concept

VLSM assigns the smallest suitable subnet to each requirement, normally placing the largest requirements first. Every allocation must remain aligned and inside the parent network; unused space remains available for later planning.

Worked example

192.168.1.77/26

256 - 192 = 64
Boundaries: 0, 64, 128, 192

77 is between 64 and 127
Network: 192.168.1.64/26

Try it yourself

Use the subnet calculator and open Show Me the Math to see the calculation for your own address.