UD-ULTCDL reduces internet spped

I have a Plugable USB Type-C Triple Display Docking Station (UD-ULTCDL) attached to a Dell XPS 13 7370.
The Display Links software is v and the XPS and windows 10 are fully up-to-date.
• My internet connection is 800 mbps.
• Attached to the plugable is:
a. One external monitor HDMI (2K)
b. A second monitor via the DVI port
c. Ethernet to the back Ethernet connector
d. 3 USB-A devices connected to the top rear connectors
e. A USB-c male to USB-c male cable connects the Station from the rear USB-c female connector to the Dell XPS

This all works well but the internet speed (as measured by the Window 10 speedtest app) is only about 200 mbps.

Here is some trouble shooting I have done.
1. I disconnected everything from the Docking Station except for the ethernet on the back connector and the USB-c cable between the Docking Station and the XPS. The speed was still only about 200 mbps, i.e. no real change.
2. I completely by-passed the Docking Station by directly connecting the ethernet to the XPS with a plugable USB 3.0 Gigabit Ethernet Adapter. Speed was then 500 mbps.

My conclusion was that the Docking Station is slowing the internet connection.

A potential solution
I removed the ethernet cable from the rear of the Docking Station and connected it to the plugable USB 3.0 Gigabit Ethernet Adapter which I connected to the front USB-c connector (all other connections remained as listed above). The speed was now about 500 mbps.

Is there any explanation for all this?

Hi Mark,

Thank you for contacting Plugable! I’m sorry the speed of the Ethernet port on UD-ULTCDL isn’t as high as expected, and I’ll be happy to help.

Thank you as well for all of the troubleshooting you’ve already done.

Especially if the same Ethernet cable provides much faster speeds when connected to a USB-C Ethernet adapter plugged into the front port of the UD-ULTCDL, that would indicate that the Ethernet port on the dock is the part having the problem.

The DisplayLink driver you indicated is currently being used by the dock is quite a bit older than the version we currently recommend. This driver runs the Ethernet port on the docking station, so as a starting troubleshooting step we’ll want to perform a clean reinstallation to remove the existing driver and install the currently recommended version. Please follow these steps:

  1. Disconnect the dock from the system and please remove the power cable from the dock so it turns off completely (this is important so the unit resets). Please keep it disconnected until the last step
  2. Uninstall any and all software with ‘DisplayLink’ in the title that is present from within the Control Panel > Programs and Features. Don’t worry if these entries are not present or if the process does not work, just move onto the next step
  3. Download, extract and run the DisplayLink cleaner tool (https://plugable.s3.amazonaws.com/bin/DisplayLink/DisplayLink+Installation+Cleaner11.2.1383.0-EXE.exe)
  4. Once the Cleaner has been run, reboot your computer (even if not prompted to)
  5. Download and install the DisplayLink software (https://plugable.s3.amazonaws.com/bin/DisplayLink/DisplayLink+USB+Graphics+Software+for+Windows11.2+M0-EXE.exe)
  6. Reattach the power cable to the dock first. Once the dock is powered on, reconnect the dock to your system​​

Please let me know how this works out, and feel free to ask if you have any questions.

My apologies for the frustration, and thank you for giving us the chance to help.

Plugable Technologies

Since posting the slow internet problem above, with excellent support from Sam in Plugable support, I have spent many hours attempting to find the problem. With Sam’s suggestions above and some others he made, I have:

  • Removed all devices from the docking station, except the ethernet
  • Tried the latest DisplayLink driver: Version 11.3 M0 (not yet “approved by Plugable” so use at your own risk)
  • Using the Docking Station with a different laptop

Nothing worked and the only way to get “full speed” was to connect ethernet via a plugable USB 3.0 Gigabit Ethernet Adapter connected to the front USB-c connector as I indicated in my original post.

I can only conclude that docking station likely has a design, hardware, or firmware issue. Unfortunately, my warranty has expired so I cannot get a replacement. Further, the Model I have - Plugable USB Type-C Triple Display Docking Station (UD-ULTCDL) - was replaced the month after mine was purchased (November 2020) with a model of exactly the same model number (UD-ULTDCL) but with significantly different features (that in itself is questionable product management; and raises doubts about the company’s transparency of issues with the model I have).

(If anyone reading this has a UD-ULTCDL purchased prior to December 2020 and has slow internet, please reply to this posting. If you don’t have an ethernet adapter to test as I did you can find them on Amazon.)

So would I buy another Docking Station from Plugable? Given there are now so many alternatives that are often less expensive I doubt it. The only saving grace is that the support I received trying to troubleshoot the problem was excellent - thanks, Sam

Hi Mark,

Thank you very much for your detailed feedback here.

First off I want to apologize again for the trouble, and thank you for all the time you have spent with us troubleshooting this issue.

You’re totally correct that there was a hardware change for the UD-ULTCDL back in late 2022. This change was initiated primarily based on customer feedback, but of course with any change to complex electronic devices like docking stations there can be other unforeseen implications that come with changing the design despite best efforts to catch everything.

I’d like to echo your call for any other users who experience similar speed issues with the Ethernet port of the original version of UD-ULTCDL, or any other dock based on the DL-3900 chip, to share their experience here. We’d always like to know if a product is underperforming so we can do our best to rectify the situation.

If you’re curious about which version of UD-ULTCDL you have, you can find a handy guide on how to identify it here: https://kb.plugable.com/question/1586094

To be fully transparent, we normally expect users with UD-ULTCDL (or any DL-3900 based dock) to be able to achieve much better Ethernet speeds than you were seeing. The Ethernet port in this dock supports up to 1Gbps through the dock’s Ethernet port, however 1Gbps is just a theoretical maximum. In real-world testing we’ve observed maximum speeds between 500-700Mbps through UD-ULTCDL depending on connected displays and possibly other attached devices, due to overhead with the DL-3900 chip.

Please also note that this speed only applies when using the dock with Windows computers. There’s currently a problem with DL-3900 based docks in macOS where the speeds of Ethernet ports can be significantly reduced. This is an ongoing investigation which has yet to be resolved unfortunately. More details about this problem here: https://kb.plugable.com/question/948146

Thank you again for your patience and cooperation through this tricky situation, and have a great day!

Plugable Technologies

This topic was automatically closed 20 days after the last reply. New replies are no longer allowed.