My housemate has Linux. Today I unplugged his ethernet cable from the household router and plugged it directly into the modem, before shutting down all other computer equipment and leaving the house for the day. Severe storms were expected. The cable company owns the modem and readily replaces it, but I own the router.
My housemate promptly lost his internet connection for the day. His connection was restored when I plugged his cable back into the router, connected the router to the modem, and booted up the router.
I've done the same thing before and he did not lose his internet connection. I don't know if I rebooted the modem. It's the only thing that would have happened different.
Whenever I unplug my Windows computer from the router and connect the ethernet cable directly to the modem, the internet connection won't work until I enter the Netshell command in a command prompt window. The Windows Netshell command resets the TCP stack, in Windows. It is unclear whether Roadrunner ISP deliberately corrupts your TCP/ IP stack to prevent connecting computers to their network, or the router does that, though I've had the problem with more than one brand of router.
Is there a similar procedure for Linux?
I've searched on the Internet, and found theoretical, convoluted and seemingly nonresponsive, answers that pertain to something different, and answers that pertain to some different operating system like Ubantu. I've seen advanced discussions about what some OTHER procedure is.
The only thing that will make sense to me is the simple command or commands to reset TCP in Linux.
The solution must NOT reset all of my housemate's OTHER computer settings or whatever to their default whatever. ONLY the Internet connection.