I just switched ISPs from Spectrum 200/10 (down/up) to AT&T Gigabit fiber (~940 down/up). AT&T provides a combo fiber modem/router that I connected directly to my existing Asus TM-AC1900 router so as to keep all my existing router configurations, etc. With wired Ethernet connections directly to the AT&T router, I get about 940 Mbps up and down on two different laptops. With a similar wired Ethernet connection to the Asus router, I get only 340 down and about 800 up. I thought the Asus router should handle gigabit speeds over its wired ports. Have I misunderstood its specs or might I have something misconfigured?