Too many USB hubs


I get this error with my Plugable docking station. It does not happen with my Surface Dock 2. It does not happen with my Dell dock. I’ve tested all three docking stations with the same laptop, the Surface Laptop Studio.

I do have a weird kind of set up. I have a small USB hub under the front edge of my desk that’s currently plugged into a different USB hub, which is plugged in to my KVM switch. I know, I know… that’s a lot of USB hubs. I wanted to be able to make it so that no matter what is plugged in, it would be available between both computers. Despite the fact that this is probably a dumb idea and not best practice, it still only happens with the Plugable docking station and not the other two. Any ideas?


Thank you for contacting Plugable support! Sorry to hear about this issue. I’d be more than happy to assist you.

There are hard limits for how many hubs can be plugged into each other. Typically this is a maximum of 5 hubs (Host system USB connection → Hub → Hub → Hub → Hub → Hub).

As the TBT4-UDZ has multiple hubs inside that are cascaded, this is counting against the total for how many external hubs can be connected together. Your other docks may not have this issue as they may have less internal USB hubs cascaded off one another. To solve this issue you will ultimately need to reduce how many hubs are connected to each other, or rearrange your hubs so that there are less “layers” of hubs deep.

For example, if you connect your first external hub to one of the 10Gbps ports on the TBT4-UDZ this may help as the 10Gbps ports on the dock are from the primary hub chipset (the most “upstream” hub to the computer) in the dock. It’s also important to note that your external hubs may also have multiple chips in them as well, so you may need to experiment with what port you use to connect them together.

As an example, most 7 port hubs would have two hub chips inside, so 4 of those 7 ports would be cascaded off the first hub chip inside and be another layer deep (“downstream” from the first hub chipset). So if you wanted to connect another hub to this example hub you’d want to connect to one of the other 3 ports that would be the most upstream to the computer.

An example of a common 7 port hub layout:
Outdated) Troubleshooting the USB3-HUB-81X USB 3.0 7-Port Hub - Plugable Knowledge Base
So in this above example if you wanted to connect another hub to this 7 port hub, it would be best to connect to ports 5, 6, or 7 (of course this will vary depending on what hub is used and how many ports there are and how it’s been designed internally).

Please don’t hesitate to let us know of other questions.

Thanks again for contacting Plugable support and best wishes!

Joshua Henry
Senior Engineer | Product Owner
Plugable Technologies

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