I needed a local wireless network to connect a set of notebooks for local multiplayer gaming with separate notebooks/PCs. In order to keep latecy low, I wanted to connect the notebooks to my old wifi router, situated in the same room as the clients ("local wifi router"), and create a wireless uplink to the internet of the "main wifi router", to provide internet for the guests.
Several related questions showed that directly connecting the two wifi routers wirelessly was unfeasible or difficult (e.g. installing unsupported third-party firmware). Since there was a cable-based alternative solution based on existing hardware no new hardware was allowed.
What I did have around was old notebooks and said old wifi router.
Best Answer
You do not want to connect the "Internet" Port of your old router to the LAN port of the new router. This can cause all sorts of NAT & port forwarding issues. Also your old router likely has a slower WAN/Internet port wich would limit the speed of traffic between devices.
Shutting down DHCP and connecting the LAN to LAN port of both routers effectively turns your old router into an access point only.