"IPCONFIG /ALL (in a command line in Windows) will tell you under the heading Default Gateway."
Then I logged in, and changed my modem's password. Does this change my external IP address?
Your modem/router might keep logs on which IP the DSL was registered to. Usually the modem's logs/UI is accessible by navigating to its IP through your browser.
How do I access these “logs” of all past IP addresses? Which tool below shall I click?