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What is a Variable Length Subnet Mask?

Published date: 28 August 2019

Variable Length Subnet Masks (VLSM), is a non-classful mask applied to a classful IP default mask. The defaults are:
Address Range Mask

Class A - (8 bit mask)
Class B - (16 bit mask)
Class C - 255.255.255 (24 bit mask)

All masks of other values for each of the classes are of variable length.

Legacy KB System (APS) Data: RESL173801 V1.0, Originally authored by on , Last Edited by on
Related ranges: Modicon Quantum

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