We have a lot of devices in our home so I recently upgraded our internet speed (spectrum) from 100mb to 400mb due to lag on online gaming. I'm now seeing on online reviews that our router only supports up to 100mb on the ethernet port, do I need a new router to get the best out of the new plan?
.... do I need a new router to get the best out of the new plan?
Yes.
According to Netgear's manual for this device, not always the most reliable source of information, the LAN and WAN ports support only 10BASE-T or 100BASE-TX. (Actually the manual I have says 10BASE, but that is a mistake.) That makes it slower than many newer internet services and most modern network hardware. Newer devices support at least 1000BASE-TX.
In your case, the 400 Mbps Internet is much faster than your router can handle. The R6120 was pretty well the cheapest router in Netgear's range. It is surprising that it produced something that slow in 2019.
The 100 Mbps speed limit applies to the link between the modem and the router as well as any traffic on your local network. You should also check that your modem can deliver more than 400 Mbps to a router. This is probably the case as 1000 Mbps has been the standard for a decade or more.
