The Velop system is designed to replace your old router if you follow the app instructions. However if you pretend that your existing router is the Internet gateway (cable model/DSL modem/U-Verse gateway) then you can plug your Velop into one of the existing router's LAN ports... just tell the app that you have connected you first Velop node to your Internet modem and it should work fine. Here is the limitation: Since the Velop will think you've connected it directly to the Internet gateway it will consider that connection to be a WAN connection and hide it behind its firewall. When you connect to the Velop WiFi you will notice your subnet and IP addresses are different from your routers IP address settings. This means that the new Velop WiFi network will not be able to see the original router LAN network. Internet access should work perfect. What will not work automatically for example is this, if you have an iPad connected to the Velop WiFi and you have an Xbox connected to your original router and then you try to use the Xbox app on the iPad it won't see your Xbox. Another example is, if you have a WiFi printer on your original router LAN it will be hidden from any device that connects to the new Velop WiFi network. The Velop app does appear to have settings that you can adjust to allow certain IP address to communicate through the firewall but I have not tested these settings.