I just got my hands on a Realtek RTL8127 10G network interface card from AliExpress, but I'm running into some issues getting it to perform at its full 10G capacity. Windows is displaying the link speed as 5000/5000 Mbps, even though I've set it to 10Gbps Full duplex. I'm connected to a 10G RJ45 switch, going to another machine that has a working 10G NIC. However, during tests with iPerf3, I'm only seeing speeds slightly under 5Gbps. I've also made sure to use the latest driver version (1127.28.50.1224, released on 24/12/2025 from the Realtek site), and it's plugged into a PCIe Gen4x1 slot. Has anyone else dealt with this issue and found a solution?
2 Answers
First off, check your cables! Are you using CAT6 or 6a? Standard CAT5 or 5e cables aren't rated for 10G speeds. Also, what switch do you have? That might be part of the problem.
You should also consider whether your CPU and storage can keep up with those speeds. Windows does have some overhead, so getting a full 10Gbps might not be possible, but it shouldn't be halving your speeds either.
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