Solved Realtek USB-C Ethernet adapter issues with Win 11

Hi

I wonder if anyone is having similar issues to me and can shed any light?

I have a full fibre connection (capped at 100Mbps download and 30Mbps upload).

I have a laptop (ASUS Vivobook S513EA) running W11 24H2. I get the capped rate (100/30) of the connection over wireless (Intel AX201 WiFi6) to a Zyxel Router (EX5401-B1), within range obviously.

If I use a USB 3.2 (A) ASIX (AX88179) adapter I get similar returns. If I use the USB-C Realtek (RT8153) adapter the u/l is fine and the d/l is somewhere similar at 25-30Mbps when I connect via homeplug. This disappears if I connect directly to the router LAN. This business with the adapter being slow seemed to coincide with the update to 24H2. I noticed that SkyGo (720p!) started to judder and go a bit blocky.

I only have 1 other USB-C enabled device (Lenovo E570) and the issue is not present with W10 22H2 connecting to homeplug nor router LAN.

This seems to rule out faulty hardware (USB-C adapter).

Homeplug speed point to point is 180-200Mbps, there are two TPLink TL-PA4020 KIT (house AIO PC running W10 and GbE switch serving BD/TV/STB/PVR) and two TL-WPA8631P KIT (router and 3-way at gaming PC).

It gets deeper. Issue also observed on Sagem router (TTSuperHub) to TL-PA4020P KIT (router and W11 PC). The W11 PC is running 24H2 (custom built Gigabyte H510M H, 16GB RAM, Intel Pent G6500 with onboard Realtek GbE). Observed WiFi is 60Mbps+ (it is FTTC; line stats are 63Mbps d/l/9Mbps u/l) but the LAN is 25-30Mbps on d/l. Homeplug speed point to point is over 400Mbps (much closer in the house). The issue is present on both LAN adapters (using the laptop) when connecting to that PLA. (No reading taken at the modem/router LAN ) The issue is recently observed and before upgrading to 24H2 (W11 23H2).

All the TP-Link kit is checked for firmware (latest), all have been restarted. All are running in Public mode (don't shoot me, it's really not a risk), all have power saving OFF.

So the only commonality I have is TP-Link Homeplugs and Realtek hardware and 24H2?

If another pair of eyes can follow my logic (?) and suggest or confirm / state the obvious I'm missing please? Be kind

@JacksonS

I don't know anything about all that networking stuff.
But... I do know you filled out your computer specs, so here's ten cookies.

Okay. USB-C is either way, right? Wrong. The cable is, but the port isn't.

I always put the adapter in a certain orientation (logo up to me, the other direction doesn't have a logo). Out of pure luck, I put it in the "wrong" way. The important distinction is that the D+ and D- are only on one side of the USB-C port. Either the pin is making a poorer connection or one of the wires has damage.

In USBDeView (a great tool BTW) the current draw is slightly higher in the "wrong" position. Also, when resuming from sleep the device is more prone to USB disconnects (just discovered) with the cable inserted the "right" way.

The RT8153 W11 driver is the same as the W10 driver here, just with a different label.

So, without referring back to the other observed issue, I am fairly confident this is a poor pin connection on the PLA, either the ethernet cable pin has been pushed down into the plastic of the RJ45 connector or some of the adjacent pins are "high" (manufacturing tolerances possibly?) or one of the PLA wires in the socket is bent, dirty or corroded. I will have to revisit that at a later date as it's not at my location.

So, I conclude this issue SOLVED!