Router-Internet Speed using Nighthawk App

Michaelkenward, perhaps I am confused? Is it not the case that the Nighthawk App reports the download speed received by the router (RAX120) directly from the modem (CM1200), because the speed test is actually running on the router itself? As a result, this measurement should be as pure and as accurate a reflection of the supplied Internet speed as is practically possible – and, therefore, should be reasonably close to 1000Mbps, which is the advertised speed from Xfinity?

P.S.: The article you referenced (Wi-Fi 4/5/6) is very informative – especially Appendix D (“Router WAN to LAN/WLAN throughput”).