Having an ISO file on a network share or external hard drive means you can reinstall the development environment years later, even if Microsoft changes the download links or retires older versions of components.
vs_community.exe --layout C:\vs2017offline --add Microsoft.VisualStudio.Workload.ManagedDesktop --add Microsoft.VisualStudio.Workload.NetWeb --lang en-US : Copy the folder to your offline machine and run the inside it with the switch to ensure it doesn't try to "call home". Scott Hanselman Create an offline installation - Visual Studio (Windows) visual studio 2017 offline installer iso