Realtek8127 10g nic only showing as 5g in windows 11
Posted by minilevy1@reddit | buildapc | View on Reddit | 11 comments
I've just bought a new RTL8127 10G NIC off AliExpress, and I've been trying to get it to work at the full 10g speeds, but windows shows it as 5000/5000 Mbps aggregated link speed even when it is set to 10Gbps Full duplex for speed and duplex.
I have it connected through a 10g rj45 switch to another machine with a working 10g NIC, but the best speeds I can get through iPerf3 are just shy of 5Gbps.
I have the latest driver version I can find, 1127.28.50.1224 released on 24/12/2025 downloaded from the realtek website. I have it plugged into a PCIe Gen4x1 slot.
Has anyone else had any issues with this chip and have fixed it? Thanks
Worried_Regret666@reddit
have the same problem, works like a charm on linux but only with 5gbe on windows 11 ltsc iot, even with proprietary rtl drivers
x_X_Fou@reddit
I'm having the same problem on Win11. My switch says it negociate at 10G, but under windows it's declared at 5G, and speedtests are capped at 5G.
I'm baffled.
xthelord2@reddit
can CPU and storage handle that bandwidth?
minilevy1@reddit (OP)
I have a 7800x3D, so it should be able to handle at least over 5g speeds. I doubt the overhead from windows would halve the total speed when testing with iPerf
xthelord2@reddit
is it at PCIe gen 3 or gen 4? because gen 3 x1 is 8gbps, gen 4 x1 would be 16gbps
this also depends on your storage, firewall settings and the amount of streams you use
minilevy1@reddit (OP)
its in a gen 4 x1 slot. Slot 3 of asus prime b650m-a wifi ii motherboard. Here's a snip from asus website "PCIe 4.0 x16 slots (support x1 mode)"
xthelord2@reddit
yes but is it set as gen 4 in UEFI?
Emerald_Flame@reddit
Are you using a CAT6 or 6a cable? 5/5e doesn't officially support 10Gbe.
minilevy1@reddit (OP)
Tried with Cat 6a & 7 with same results.
Emerald_Flame@reddit
What switch are you using?
And if it's going into an SFP port, what transceiver?
minilevy1@reddit (OP)
Unifi Pro Max 16, SFP+ port 1 (home server) using an ipolex ASF-10G-T transceiver, SFP+ port 2 (windows desktop) using a group-win PAC-10G-T transceiver. swapped them around and even connected directly to the home server, still only 5g speeds