Tools

Enter any IPv4 address with a prefix or mask and get the network and broadcast addresses, usable host range, host count, wildcard mask, class and RFC 1918 status, with the binary shown.

Give it a base network and the hosts each subnet needs; it allocates largest-first, non-overlapping subnets with network, mask, usable range and broadcast for each, exactly as a CCNA VLSM question expects.