Use case: Home WiFi with many devices causing interference and intermittent DHCP issues, especially if many devices are already in a room with poor WiFi signal strength.
By doing this I saw a 5-10x increase in throughput to each of my connected devices--my security research lab--and a drastic reduction in the occurrence of "connected but no internet access" situations. YMMV.
- Connect an Ubuntu Machine to WiFi
- Plug Ethernet cable into Ubuntu Machine's Ethernet port and a spare router's WAN port (the one normally plugged into the wall/modem).
- Open Ubuntu connection settings (toolbar network icon -> Edit Connections / Wired Settings, or run nm-connection-editor in terminal).
- Double-click wired connection name
- IPv4 Settings tab -> Method -> Shared to other computers
Bingo! All devices connecting to the router will have internet access to the outside world, and won't have to compete with a houseful of wireless devices for a signal.
This is very useful for reducing interference in rooms with many WiFi devices, e.g. a home security research lab. The advantage is twofold: reducing interference (only one machine needs to remain on the primary WiFi channel), and boosting your signal by acting as a pseudo WiFi repeater. Better yet, connect nearby devices to the secondary router with additional Ethernet cables. This essentially creates a two-tired network topology that spreads traffic between multiple wireless channels and subnets. Neat, eh?