CB-C71 HUB Ethernet while charging PD port

Hi,

I’m considering to buy CB-C71 USB-C hub.
I’ve tested several USB-C hub with PD charging and ethernet port and found almost all those hubs have problem with ethernet when USB-C port is disconnected (PD charging port is still connected).
Some are reported in reddit:


Did anyone test if the problem occurs also with this USB-C hub?
If there is no problem with this hub, I’ll definitely buy this one!
Thank you in advance!

2 Likes

That was a really interesting read. I hadn’t even thought about the possibility of a powered USB-C hub causing a broadcast storm without a computer plugged in, something to keep in mind for the future.

Unfortunately I can’t tell you about that specific hub, hopefully support here can give you a clearer answer. I have an older Aukey hub and have never had any of those sorts of issues with it, but I have not been using usb passthrough - so it isn’t powered up to even send packets when off.

On the upside, Aukey support is excellent. So if you get one and discover it does cause the issues, they would be able to help you out - whether to fix it or let you return it if it is dysfunctional in that way.

I have a hard time imagining that this is a really common problem. Broadcast storms are very hard on networks, and I would expect to have heard about this much more widely if it were common.

Oh, this is a very strange problem that I have never thought of.
Our dev team will run several tests to find out if the same issue occurs to AUKEY hubs, and I will keep you updated once there’s a result.

5 Likes

That’s great support from aukey right there :grin:

2 Likes

Hi, I just tried CB-C71 and another upcoming hub myself with coworkers’ MacBooks, and so far there’s no broadcast storm. Let’s wait and see if our dev team could find any other bugs.

3 Likes

@furushchev I actually did have an issue with network storm with the CB-C71. My home network setup is Main WIFI Router -> 4 port unmanaged Switch -> various home network entertainment devices + USB-C Hub for laptop + 2nd WIFI Router in AP mode dedicated to Smart Home devices such as speakers/thermostats/etc. Don’t know if it’s the unmanaged switch that was not stopping the broadcast storm as I didn’t really troubleshoot but once the storm happened, every device hooked up to the network switch (basically the entire house devices minus phones and laptops) would disconnect.

I don’t have this problem with some other USB-C Hubs with ethernet that function similar to the CB-C71

2 Likes

Thanks for reports and the further investigation by support team! :slight_smile:

I’d be better if we know hubs without network storm to isolate the problem by testing them on the same environment if there is no problem to post here.

Anyway, let’s wait for the feedback from dev team.

1 Like

@simonyahn Thanks for the reply!
Hmm, I should wait for the feedback from dev team…

I have the same issue on my environment (with VAVA USB-C hub that I have).
The configuration I have is:
ONU -> Wifi Router -> 3 x Switch

There are many clients (ubuntu/win10) connected to Wifi and to switches by wired connection.
I connected the network port of the USB-C hub to one of the switches with ubuntu/win10 computer connected to USB-C port, and found that all connection w/ devices are lost when disconnecting the USB-C port while charging USB-C hub.

It was really touch work to find the cause of the network problem since I’ve never thought that the USB-C hub goes mad if the computer is disconnected.

This really sounds like something that is probably a crossover issue between the Realtek chipsets that power most of these hubs and the way power is handled with no computer plugged in. Once power is on the chipset, the router / switch knows it has a connected device there and will try to send any broadcast packets to it. Then the chipset probably responds with an error message (possibly to the broadcast address) and that amplifies the problem.

From a design standpoint, there are probably two fixes - one, the hub shouldn’t be passing power to the ethernet chipset if no controlling device is present. But two, the chipset should establish communications to a host device BEFORE it starts responding to network packets or advertising its presence on the network in any way. Everything that comes in before that should be silently dropped.

I can’t think of much you can do about it prior to a hardware redesign or possibly a firmware fix other than set the switch to block excessive broadcast traffic. Which should probably already be true on most corporate networks, but not many home ones. Or train your users to unplug the USB-C power, but that isn’t going to be an easy task - these are meant to be docks where you just have to unplug one thing and walk away with it ready to go next time.

I have another brand USB-C hub with ethernet and PD that I want to test this against now, but it is at my office while I am at home on lockdown. So I can’t do it for a little while, but once things open up again…

How about teaching people to disconnect the hub when they are not using it?

1 Like

Good point, though If the user un-plugs the hub, and takes his laptop, while ethernet and charging is still connected to the hub… this is the usual case.

User needs to power off the charger connected to the USB-C hub, most of the time, users forget it

i myself forget to power-off the docking station when I un-dock the laptop… :smiley:

1 Like

I don’t have a lot of USB-C Hubs personally. The one I was using before was an older one that just looked clunky and was cheap off of Amazon for my wife’s 12" Macbook. There were no issues with network storm with that one and everything plugged in. I decided to buy the C71 because it checked off a lot of boxes and looked pretty good. Too bad about the network storm on my side. I was also going to get a VAVA USB-C hub but ended up opting for Uni USB Hub with ethernet (mostly because of the removable USB-C Cable and the ability to replace with longer cable). Fortunately this one had no network storm issues but there are EMI issues for the USB 2.0 port and my Logitech Unifying receiver. In the process of getting a USB extension cable to try to help with that issue.

I am debating on the Unity Wireless Hub (CB-C70) for travel though.

1 Like

Agree that these docks should be meant to just unplug one thing and not many things. I don’t want to have to remember unplugging either power or the ethernet cable from the dock every time I remove the dock from my computer. Kind of defeats the purpose of “single cable” set up.

1 Like