Calculators

Please note that the calculators are free utilities. Maintenance and support are not offered with these products.

FAQs

I am not seeing all possible subnets in the IP subnet calculator. What could be wrong?

The Allow 1 Subnet Bit option isn't checked.

Historically, subnets composed of all ones or all zeros were reserved. Therefore the minimum number of subnet bits allowed was two, which allotted for two usable subnets (01 and 10 in binary, subnets 1 and 2 in decimal) and two reserved subnet addresses (00 and 11 in binary, subnets 0 and 3 in decimal). However, RFC 1878 abolished this practice because the reserved subnets were generally not being used for any special purpose and was considered wasteful. Thus the minimum number of subnet bits is now one, allowing for two usable subnets (0 and 1 in binary, and decimal).

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