Living in a joint family we have 3 internet connections, each floor has one internet connection which is split per floor. Each internet connection is shared between 4-5 computers using a switch per floor. Each of these internet sharing networks are independent of each other.
What I want to achieve here is a local network (for local messenger and file sharing) that can combine all the 3 independent networks, problem is that whenever I try to do that the whole network tends to use just one internet connection. I have all the necessary hardware.
How do I solve this problem, one approach could be that I could get one PC to act as a server and bridge the internet connections and then the whole network would have to access the internet through this server. Theoretically this could be possible but I have never tried this approach in real life.
Also if certain computers need be restricted from internet access how would this be possible on the same network?
Edit: Also can I remote into any of the computers on the network to troubleshoot common issues
(like grandma deleting the Firefox shortcut for the nth time and screaming "Google does not work any more")