IP Subnet Calculator for IPv4 and IPv6

From Bitcricket:

Input an IP address and choose one of the following: number of subnet bits, the maximum number of desired subnets, the number of host bits, or the maximum number of desired hosts. The calculator gives you a bit-by-bit address visualization and generates a complete table of subnets. CIDR allows multiple IP routes to be aggregated into a smaller set of routing table entries. Just as with subnetting, the calculator makes it easy visualize and generate CIDR information. The calculator is the first to support IPv6. Although there are no subnets in IPv6 per se, there are several different types of IPv6 addresses and bits/fields within those types have different interpretations. Enter an IPv6 address and we classify and dissect it for you. The calculator automatically discovers locally configured IPv4 and IPv6 addresses, allowing you to quickly classify and dissect them. The information presented in our calculator is a mere cut-and-paste away into your favorite application.

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