Wanting to Separate Modem/Router unit into 2 units
Oh so you have fiber? If so, the Panoramic gateway is actually only acting as a router. The modem inside has already been disabled. That means you can't use bridge mode because that disables the router inside, and you can't disable the modem AND the router, because what would you have left? However, because it's working as a router, any other normal router can do it's function. You just need a wifi router with a Ethernet WAN port and DHCP compatible, which is most routers. You can't go by how many ethernet ports are on the device anymore because some modem/router combos only have 2 LAN ports, and some stand alone modems have 2 or even 4 ethernet ports. You can only use 1 of those ports for service unless you have a business account that allows multiple IP addresses. So what you are looking for is a device with a ethernet port marked WAN. Sometimes it will be labeled "internet" and will usually be a different color.
What speed do you pay for? What kind of wifi devices do you have? Wifi 5/6/6e/7? Did you have a budget? The gl-inet Flint 2 router is a great choice for any speed service as long as you are fine with wifi 6.
