I'm having a huge issue with my new build where the Ethernet is stuck at 100 Mb/s and my Wi-Fi won't go above 120 Mb/s. It's honestly driving me crazy! I've spent over six hours trying to troubleshoot this. Every other device on my network is getting significantly better speeds—like 400-600+ Mb/s on Wi-Fi and 650-700+ Mb/s on Ethernet—using the same cables and modem port. I've already tried a bunch of things: swapping multiple Cat-6 cables, connecting directly to the modem, power-cycling everything, updating the BIOS, clearing the CMOS, and even doing fresh installs of Windows 11 and Pop!_OS. I've messed around with all the Realtek drivers without success, and I even disabled various settings aimed at conserving power. No matter what I do, my Realtek NIC just won't negotiate beyond 100 Mb/s, and the Wi-Fi is pretty dismal too. I'm at a loss and really just want to get my dream machine working as it should. Anyone have any other ideas before I consider returning it? Is there a possibility that the RTL8125B has a hardware defect?
4 Answers
Definitely check your chipset drivers! Also, if you've got an MSI board, avoid installing the Killer network app; it can mess with settings.
Check the specs of your NIC in Device Manager. Make sure "Auto Negotiation" is enabled for the best speed. Also, ensure it’s not set to 2.4GHz only. Right-click your adapter, go to properties, and check the Advanced settings—there should be an option for preferred band. If nothing seems to work, you might consider getting a new NIC or even a USB Wi-Fi dongle to troubleshoot further.
If your Ethernet isn't linking at gigabit while other devices are using the same cables and getting good speeds, it's likely a bad network interface card (NIC). Honestly, I'd just pick up a PCIe NIC and call it a day! It might be annoying to think about an RMA, but for around $30, a new card could save you a ton of hassle.
My Ethernet link through the motherboard said 100/100, but when I used a USB-C dongle, it jumped to 1000/1000! Maybe that's an option for you to consider in the meantime?
Wow, that's interesting! I'll definitely look into a USB option while I figure this out.
Thanks for the tip! I'll make sure to check the chipset drivers and skip that Killer software.