Networking – How to turn Ethernet extension into a WiFi Hotspot

Connect all the APs via Ethernet cables to a central switch, each AP on a port.

Connect the switch to the router via back-to-back Ethernet cable using one port only.

Assign default gateway ip address on the router port connected to switch, say 192.168.1.1/24.

Disable DHCP and/or NAT (if avaialable) on all APs.

Configure ip addresses on APS (if mandatory), E.g. 192.168.1.2-5/24 for 4 APs. You can use those IPs for managing the APs.

Run DHCP from the router (unless you have another DHCP Server), e.g. 192.168.1.10-50/24.

This will create a single network segment for all hosts connected to the APs (or Switch in general), and the default gateway will be the router.

Hosts on this segment will now talk to each other directly via the switch.

You can use same SSID for all APs, and you can set each to a different channel (1, 6 or 11) to minimize interference.

This is a basic setup, there are other possibilities, depending on requirements.

You could look into a wireless bridge (or WiFi bridge). This may be the component/term you're looking for in your situation. It's basically a reversed access point and it's a feature some WiFi routers have built-in. You connect it to an existing wireless network and it then "outputs" the network on its ethernet port or ports, usually acting as a switch depending on how you configure it.

A second option might be powerline networking. It's a technology that uses existing powerlines in your home (yes, using the sockets you plug your toaster or microwave in) to piggy back network signals. However, this is very dependent on how your home is wired and your mileage may vary in terms of speed, latency and stability.