Is your feature request related to a problem? Please describe.
I work with network appliances in my day job and I have to be honest, I'm a big dummy when it comes to remembering the comparisions between CIDR and the subnet mask. The appliances I work with sometimes accept the CIDR while other times will only accept the subnet mask, so having a tool to calculate the appropriate counterpart would be valuable.

Describe the solution you'd like
Add an operation which converts between the CIDR and subnet mask. It would be nice if the "Parse IP range" operation would also accept masks in addition to the CIDR.