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U4021QW, clarification on RJ45 network connectivity
I'm over the moon with my U4021QW monitor (Service Tag: ), but I have a question about the network connection between its RJ45 and Thunderbolt sockets.
I have a Latitude 3420 (Service Tag: ) connected to the Thunderbolt input on the monitor. Rather than connect the network to the laptop, I connected the network cable to the monitor's RJ45 input, as per page 37 of the User Manual. This is a neat solution - a single cable to the laptop charges it, provides a network connection, carries 5k video plus audio and supplies keyboard and mouse input (both connected to the monitor).
My issue is that when I switch the monitor to another input (e.g. DisplayPort for my desktop PC), I appear to lose the network connection via Thunderbolt to the laptop. Irritatingly, this causes the laptop's VPN to drop and I have to do the whole PIN, password, re-connect, every time I switch back to the laptop.
Is this the intended design? The User Manual says nothing about RJ45 connectivity. It would be really useful if the behaviour of the network connection could be described fully, so that I know what to expect.
In the short term I'll just pull the network RJ45 from the monitor and connect it directly to the laptop - but that's a little more untidy! Am I being unreasonable expecting the network connectivity to be sustained at all times (like USB power)?
TalldaveUK
49 Posts
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September 20th, 2021 07:00
Dell staff have very kindly investigated and fed back on this issue. The network connection is switched from UCB-C to UCB-B as part of the KVM functionality and further testing on my setup confirms this.
Unfortunately, therefore, in my setup I cannot use the monitor's network connection and will stick with direct network connections to each computer.
My only frustration is that there is no mention of this functionality in the user manual (that network is switched with KVM) and in fact pages 66/67 of the user manual describing keyboard/mouse connection have no network connection shown - and hence it never becomes obvious that it is switched.
Hopefully Dell will consider adding clarification of the network functionality in the user manual.
Thanks again for the assistance provided.
jphughan
4 Operator
4 Operator
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14K Posts
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September 14th, 2021 12:00
@TalldaveUK That is very strange. I would have expected the network interface to remain available over Thunderbolt even if a different input was in use, and I can't immediately think why that wouldn't be the case. It's not as if it's being switched to be made available through some other upstream data path to a different system, after all. But if you can't find anything in the on-screen menus to customize this sort of behavior, then I would imagine the only thing you could do would be to wait for a possible firmware update in case this wasn't intended and can be fixed that way. Hopefully it is indeed an oversight of some kind because I can't see why this would be a deliberate design choice.
On a side note, it's never a good idea to post Service Tags on a public forum. At a minimum, those can be used to file fraudulent ownership transfer requests for your equipment, which can make it more difficult for you to prove your ownership and obtain warranty service, for example.
DELL-Chris M
Community Manager
Community Manager
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54.4K Posts
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September 15th, 2021 04:00
Test 1 =
* On the Latitude 3420, open the Device Manager (Windows + X)
* Open Network Adapters
* Double-click Realtek USB GbE Family Controller
* Click the Advanced tab
* Change "Idle Power Saving" to Disabled
* Click OK
* Close the Device Manager
* Now retest going to Desktop PC DP (DisplayPort). Does the Latitude 3420 network connection still drop?
Test 2 (Not sure if this has anything to do with network, but checking anyway) =
* Connect the provided USB-B to USB-A cable from the U4021QW to the Desktop PC. Retest going to Desktop PC DP (DisplayPort). Does the Latitude 3420 network connection still drop?
TalldaveUK
49 Posts
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September 15th, 2021 12:00
Thanks for the feedback. Testing took a while as I don't have admin access so have to rely on a remote IT support session using Any Desk - which gets cut off when the network drops every time I switch away from the Thunderbolt input!!
Test 1 - network still disconnects.
Test 2 - this cable is already in use to provide keyboard/mouse/webcam input to the desktop PC. I can’t operate without it.
As far as I can tell, switching away from the Thunderbolt input seems to disconnect the network. If I have the laptop audio set to use its internal speakers (rather than the monitor's speakers that I'd normally use) you hear the Windows "something was unplugged" audio notification and (for example) streaming audio playback stops.
I suppose the question to ask is - is anyone else successfully using the RJ45 network via Thunderbolt when not viewing the Thunderbolt input?
TalldaveUK
49 Posts
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September 15th, 2021 14:00
OK, so I have now given up on the RJ45 network connection in the monitor and connected to the laptop directly. Now, when I switch the monitor away from Thunderbolt, I get the Windows "diddle dum" audio notification of the "unplug" of the keyboard/mouse on the laptop - and the corresponding "diddle dum" on the desktop as the keyboard/mouse/webcam are connected to the desktop machine.
My conclusion is that this USB "unplug"/"hotplug" event affects every USB connection down the Thunderbolt (OK, strictly USB-C as far as the laptop is concerned) cable; which means the network connection over USB goes as well.
I'm rusty on USB specifications, so I've no idea whether it's even possible for the monitor to "unplug" the keyboard/mouse/webcam whilst leaving the network connection running. If it's not, I would have to question why Dell have bothered to put an RJ45 on the monitor at all?
Sadly, the only downside of the RJ45 going direct to the laptop is cosmetic! The only space on my cramped desk means the laptop is lengthways towards me - with the USB-C connection towards the rear of the desk. The RJ45 is therefore facing me and the network cable is effectively sticking out the "front" of the laptop, where it's in the way. Maybe I will try an ethernet to USB3.0 adaptor in the USB socket adjacent to the USB-C connection and see if that handles the monitor's "unplugging" activity on a switch away from the Thunderbolt input.
Thanks to everyone who's responded so far.