You Can Share Internet Over Ethernet????

September 14, 2025

I’m in shock. Apparently you can connect two computers over ethernet and have one share its wireless connection to the other???? I have been dealing with devices that don’t have wireless internet for literally years, and it’s always been a struggle trying to work with them without a connection. The problem is you can’t install anything without an internet connection (obviously), which leads a dumb bootstrapping problem. I’ve spent hours getting fresh linux boxes connected to school wifi (WPA2-protected) with text configs on systems where nmcli is not installed (I can’t install it without internet!!).

I just had this same problem with my De-10 Nano SoC I’ve been using for a school project - it only has ethernet, and my house doesn’t have ethernet jacks. No internet means I have to open a TTY over serial. I had to transfer a 7 Mb binary file from my computer to the board, and I figured out a hacky solution where I literally sent the bytes through the serial connection by enabling raw mode in the tty, redirecting the bytes to a file, and then cating the bytes into the tty. For reference, the 115200 baud rate over UART means that this file transfer took $7 \, \text{Mb} / (115200 \, \text{bits}/\text{s}) = 8 \, \text{minutes}$. For every new design I compiled, a whole eight minutes just to transfer it to the board to test it. And you thought C++ compile times were bad.

It turns out I should have done a simple Google search. Apparently Windows has Internet Connection Sharing, which lets you use a computer with a working wireless connection share it over ethernet to another device (and Linux has an equivalent too). Like a Gameboy link cable. 🤦

So I can literally just connect my board to my PC with an ethernet cable and boom: internet. I guess there’s no reason why this isn’t technically possible, but I guess I just never realized it 1) actually existed and 2) was built-in to existng operating systems already. Welp, my problems have been solved (for now).