IPv4 Subnet Calculator

So I challenged the intern to a simple task. “Create an Excel file that explains how IPv4 Subnetting works.”

It hadn’t occurred to me that folks who are new may not have done a lot of this, so I created a quick introduction myself to compare results.
Here is the file. If he comes back with something, I’ll post it too and you can use either one should you need to refresh your skills on subnetting.