TB16 Ethernet speed limited at 100 Mbps

You definitely don't want to force 1 Gbps Full in Device Manager.  Forcing linespeed and duplex settings especially on gigabit connections can lead to worse performance even when those hardcoded settings are correct. The standard for gigabit is auto-negotiate.  There's a Realtek network FIRMWARE update for the TB16 and WD15 docks around here somewhere, but I don't know if that would help this issue.  But my main question is: What do you mean your Ethernet is 250 Mbps?  There's 100 Mbps and 1 Gbps.  There's no standard for 250 Mbps Ethernet.

Have you tried a different cable?  Do you have any other systems that are negotiating at 1 Gbps with the cable and switch/router port you're currently using with the TB16?

Thanks, jphughan! I've reverted back the setting to the factory defaults to get comparable results, as I was tweaking them only to see if any difference occurs.

Now, 250 Mbps is the speed I'm getting from my ISP and before I started using TB16 I was able to utilize its full speed (also using Dell's port extender on USB-C that included network port).

My Windows network settings claim to have 1Gbps connection established.

I've played with the cables obviously - I'm using Cat.6 network cables and tried 3 different ones. Tried different modem port, disconnected my additional WiFi router (even though my 9360 is connected directly to the modem). I even disconnected other peripherals connected to TB16, hoping for a difference. Nothing has helped unfortunately...

I haven't been able to find any Realtek firmware over Dell's website, the drivers page lists only three drivers which I have installed. Well, I've managed to find the Realtek GBE Ethernet firmware update, but it claims to be intended for WD15 docks only, not to the TB16, so I'm afraid to install it.

If you are showing a 1 Gbps network on the Status page then the problem is more than likely, not the TB16.

What type of Modem are you using and what company supplied it?  I went through a speed increase with the then TWC cable connection and certain modems would not handle the increase in speed.  Currently, mine is only 75 Mbps and I get that speed.  I have not upgraded to a higher speed.

You really need to be checking your speed with something else on your LAN to make sure it gets over 100 Mbps.  Right now I am not showing IPv6 Internet access so I need to work on that system since my ISP supports IPv6.

Interesting, I installed a firmware update for the Realtek LAN controller on my own TB16 and didn't have an issue, although in fairness it was listed at the time as applying to the TB16.  I'm not sure if they discovered an issue on the TB16 or if this is just a glitch in their listing, and sadly I can't even remember if I installed that exact version of the firmware update.  Still, I understand being reluctant to install that if it's not listed as applicable to the TB16.

Just fyi, on wired Ethernet, Windows will only ever report 10 Mb, 100 Mb, 1 Gb, or 10 Gb (on adapters that support it), regardless of the speed you're getting from your ISP,.  That's because the area you're checking only reports the link speed that was negotiated between your Ethernet adapter and whatever device is on the other end of the cable, NOT real-time actual throughput statistics.  For that, you can look in Task Manager and go to the Performance tab if you want.  WiFi adapters will report more possible values because the WiFi standards define more, but even there, the OS will report the negotiated link rate, not real-time actual throughput.

One thing you can check would be the physical pins inside the Ethernet connector on the TB16.  100 Mb Ethernet can operate over only 4 pins, whereas gigabit requires all 8, and I remember having a USB Ethernet adapter once where a few of the pins had gotten stuck pressed down or deeper into the connector relative to the others, and as a result, they didn't make proper contact with the cable when it was inserted -- so all of my connections were stuck at 100 Mb.  I spent a few hours trying to troubleshoot this in software before I finally took a look inside that port and noticed that some of the pins didn't look right.  After I fixed that, I immediately got gigabit. :)  That said, on that adapter I ended up having to open it up (which was easy on that adapter), but that may not be feasible on the TB16. Still, see what you find; yours may be a simpler fix.

If that doesn't do it, terms of updates, please confirm you've installed the latest version of ALL of the updates listed below, and if not, install them in the order they appear:

- BIOS

- Thunderbolt firmware

- Thunderbolt software

- ASMedia USB host controller driver

- Realtek USB Ethernet driver

If all of that looks good, then seeing as you've already tested other cables and modem ports and are able to get gigabit with that equipment on other devices, it would seem you've got a bad TB16, in which case the next step would be to call Dell Support to arrange a replacement. Sorry!

@jphughan - about the modem: I did several restarts and finally decided to bring it down to the factory settings. Nothing helped.

I've also run the Fast.com test, as suggested but it showed only 62 Mbps, which is probably due to my European location.

Seconds ago I've re-run the speed test with my network cable attached to the DA200 adapter and I got 240 Mbps...

Anyway, you must admit it would be extremely weird if the dock ethernet card malfunctioned with such exact throughput rather than providing some crazy results or failing to operate at all... Driver issue looks the most realistic to me, yet I have no idea how to fix it.

@Saltgrass - as said, I've checked the network speed with my M4800 and it was around 240 Mbps. Then I used my work 9550 connected via TB16 and I wasn't able to exceed 100 Mbps. When I attached the Dell USB-C adapter, I was again getting over 200 Mbps. Therefore I believe the issue is with the dock.

@jphughan - I confirm, the order of installing the drivers was as you listed. I've double checked my cables and they for sure contain 8 pins.

My modem is the ubee EVW3226 provided by UPC (European ISP), not the greatest one but certainly able to handle speeds higher than 100 Mbps.

My TB16 is a replacement model as the previous one has USB issues, so I'm skeptical that Dell is willing to send me another one... :( Since Ubuntu users are repeatedly reporting the same issue, I still believe the problem is with the firmware/driver, not with the dock being faulty (but that's my gut feeling only).

Most likely I need to wait for others to confirm or deny having similar issues with speeds over 100 Mbps...

Based on everything you've just said, I would say the dock is the most likely culprit, not the driver.  If it were the driver, I suspect we'd be seeing much more widespread reports of this.  I suppose theoretically it could be some driver issue specific to that LAN chipset and whatever chipset is in your modem, but that seems incredibly unlikely.  Then again, if you happen to have a way to connect your dock to another router/modem/switch, and connect THAT device to your modem, it might be interesting to see if anything changes.

Whatever the case, you shouldn't have any trouble getting Dell to send you another dock.  The fact that a previous dock had a different issue is completely irrelevant.  If this one also doesn't work, then it doesn't work, and that needs to be fixed. (However, the USB issues you had with the previous one could actually have been due to the 9360's BIOS.  Dell released some BIOS updates for a few systems, including the 9360, that caused intermittent disconnects for USB devices attached via the TB16 dock.  The good news is that BIOS 2.2.1 resolved that issue, and a new ASMedia USB driver was also released, though I don't know if that was related to this issue.)

You might also make sure your have the correct driver.  When I checked the TB16 site it originally showed the wrong OS..

I found out why some folks are having problems with the TB16 and USB ports and the devices disappearing.  I had just done a clean install on my system and had not installed the ASMedia USB drivers for the Dock.  The Ethernet was also flaky and the taskbar icon still showed as wireless and not Ethernet.

I just downloaded a large file from my NAS and got 925 Mbps.

If it isn't the modem and you have that system connected the same as your good system and if you assume it isn't the TB16 then the only thing left is the connection/wiring.  You said you used Cat 6.  Did you buy it or make it yourself?  You might want to watch the lights on the  Docks Ethernet port and see what color light is flashing and does it speed up during downloads... Just something to check to keep you occupied ;)

Hmmm... The amber LED is blinking next to the port when in use which per my knowledge suggests the 1 Gbps connection established...

I'm using cables purchased from a reliable source, so I hardly believe it's a cable issue.

Yeah, I used to have ASMedia issues as well - even though I installed the drivers, the MS drivers were used anyway by the OS. I needed to enforce the driver update from a given location and only then the real ASMedia driver got installed and the dock performance turned steady. However, my impression was that those drivers only control the USB ports, not the Ethernet, but...

Another issue is that Dell's page doesn't recognize my dock service tag. The same happened to the last dock and I needed the retailer to push Dell to actually show any interest in the case. That's why I'm a bit reluctant to report another problem, as Dell technicians will most likely tell me "I don't see this device in the system and I can't help you. Goodbye." as they did the last time. It's a awkward issue with those docks as many people report they can't register their docks if they didn't purchase them directly from Dell, but via some retailers. Crazy...

Hah, clever,  I wasn't aware of this one! Anyway, I got a full replacement, as I got a completely new dock, so hopefully no cable tricks were made ;)

Are you suggesting this may be a cable-related issue? I have no other problems with my display, USB peripherals or power.

Oh, and one more thing.  When they replaced the Dock did you use the same USB C cable or did it come with a different one?

And answering you last question :) - I got both dock and the cable replaced. In fact it couldn't have been anything else, as the cable is fixed into the dock and cannot be detached.

If you check the box the dock came in there should be instructions on how to remove the cable.  They usually ask you to that prior to returning.  Mine has a little piece of rubber covering the screws.

Just fyi, the ASMedia driver is in play because the Realtek chip sits on the dock's USB bus (that's why the driver is called Realtek USB Ethernet), and its data therefore flows through the ASMedia USB host controller.  After it's installed, you should still see the regular Generic SuperSpeed USB hub in Device Manager, but if you open the Properties pane, the Vendor on at least one of them should show as ASMedia rather than Microsoft.