Subnet Calc Pro

Subnet Calc Pro is a tool designed to help network administrators who need to keep track of the various subnets which they administer.
Inside the ORGANISER you can define subnets by selecting an IP and CIDR. You can save the subnets which you manage in a hierarchy so that you can keep track of how you have allocated and split up your subnets into smaller subnets. Also, you can add hosts inside each subnet so that you can keep track of IP allocations. For each defined subnet, Subnet Calc Pro will calculate all details including its class and even whether or not the IP is in the loopback / private ranges.
There is also a handy subnet FINDER which is an aggregator and can be used to calculate the smallest subnet which encompasses a given set of IPs. This can be useful if you need to figure out a subnet mask which will allow a given set of IPs to talk to each other.
Also included is a standard subnet CALCULATOR which is the same as the free version of the software called Subnet Calc.
Finally, you can even export all your data from the database by email.