I just got AT&T's 1 gig fiber service installed yesterday. When I ran a speed test directly from my desktop to the router via Ethernet, I was only getting about 90 Mbps. However, when I connect over WiFi, the speed jumps to around 600 Mbps! According to the smart home manager app, everything is fine on AT&T's end, but my PC's link speed seems capped at 100/100 Mbps while connected via Ethernet (I'm running Windows 11). My motherboard is relatively new (an MSI MAG B650 Tomahawk), so I find it hard to believe that the Ethernet port is faulty already. I've also tried using four different Ethernet cables, two of which were brand new. I've checked the speed and duplex settings and they're set to auto negotiation. Now I'm really stuck on what to do next, and any advice would be greatly appreciated!
2 Answers
It sounds like something is limiting the Ethernet speed. Check if both your PC and the router have Gigabit Ethernet ports; if either is only rated for 100 Mbps, that could be the issue. Since you mentioned trying all the ports on the router, it's worth double-checking that they're truly capable of 1 Gbps.
Make sure you manually set your speed and duplex settings to 1000 Mbps full duplex instead of relying on auto negotiation. Also, you mentioned using Cat 6 cables, which is great; just double-check they say Cat 6 or better on the side.
I tried setting it manually, but it still didn’t seem to help. And yes, the cables are definitely Cat 6.
I think the router should be fine since it came with the fiber install. Plus, I was able to get around 500 Mbps with my old ISP using Ethernet.