Find code and diagrams at: https://www.EliTheComputerGuy.com

Dig allows you to find public DNS information so that you understand the public infrastructure for an organization.

Find MX Record for a Doamin
dig facebook.com mx

Find A Record for Domain
dig salesforce.com a

Find All Records for Domain
dig facebook.com any

Find Records from Specific DNS Server
dig salesforce.com any @8.8.8.8