Hello, I have an old PC and a Mifi 8800l mobile hotspot. I know I can tether the hotspot to the PC, but will bridging the Mifi and Ethernet and then connecting it to the WAN port on a router produce a viable source of internet?
This is a try it and see if you can get it to work. All depends if you can actually just bridge the tether and the ethernet. You may have to run ICS which in effect makes you pc a very stupid router. You could run router behind router or you could convert you router to a AP and use only the PC.
Hard to say because tether is not ethernet so some software must convert the packet format. If it has the option to bridge the 2 it should work. All depends if that option exists, not all device drivers have it.
If your hotspot has a limit on the number WiFi clients that can connect to it (typically anywhere between 5-10), bridge mode will not be ideal. If that's all you need, go ahead and explore bridge mode solutions already mentioned earlier.
If you need more flexibility, install a router software on the old PC and use it's WiFi as WAN.
I've done it using Untangle NG and I would think that the same can also be achieved using pfSense or OPNsense (choose your poison). Free versions will suffice.
Three important things you must do:
Set the WiFi interface to Client mode (as opposed to AP mode)
Assign it as a WAN interface
Type in the SSID, encryption type, and pre-shared key for the hotspot
Assign one of the wired Ethernet ports on the PC as the LAN and connect a standard Ethernet switch so you can share the connection
This is not bride mode so any number of devices connected to the PC/Firewall LAN interface will be able to share the hotspot connection, with only the bandwidth limiting performance.