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Variable Length Subnet Mask (VLSM) Calculator

This calculator enables you to determine:
  • The length (in bits) of a network mask given the dotted decimal
  • The dotted decimal network mask given the length
  • The number of hosts and subnets given an IP address and network mask
Note 1: If the network mask is specified by both dotted decimal and length, the length is ignored.
Note 2: This calculator assumes classful addressing (not CIDR).
IP address:
Network mask (dotted decimal):
Length of network mask (# of bits):
Print all subnet numbers:



VLSM Calculator

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