Variable-Length Subnet Masking. A
subnet address assignment
scheme in which each physical network can have a different mask. The primary advantage is flexibility; however, there is a possibility of address ambiguity, in which an address can be interpreted depending on the physical network. VLSM is useful in a situation where each link in an
internetwork must have its own subnet address, each of which in turn must have enough host address to accomodate all attached devices.