Can't Windows support Wi-Fi and LAN simultaneously?

This is tangentially a Windows 10 issue; I experienced the same thing under Vista previously. Obviously I just need to understand how Windows, in general, handles this.

My Dell desktop, running Win10, connects to the outside world through the house Wi-Fi router. This works fine. However, I do have occasional need to connect directly to hardwired (LAN port only) equipment I'm working with, and it's not convenient to run a 100' cable from my desk to the router in the attic. So I plug a LAN cable from my computer into a second router, an inexpensive 4-port wired-only type just sitting on my desk, and thus make direct connection with the hardware I need to address. This works fine too.

My Network & Internet Settings page shows both the Wi-Fi and LAN connections, but they can't be used at the same time. Maybe a conflict between DHCP activity with two routers or something? I have to disconnect or disable the LAN port to get back on the Internet via Wi-Fi, and vice-versa. Is this just the nature of the beast, or is there some way to have both ports active at the same time without a hardware reconfiguration?

It should work properly. I would suggest setting a hardcoded IP, subnet, and gateway for the wired connection. See if that works any better.

If the second router is just for LAN then don't give it a gateway that causes the problem

Use the second router as a bridge if the two are connected. Only one should have DHCP unless they are on completely isolated networks.

Cereberus, that's an interesting bit of kit. From the title in the Amazon listing, it seems that little box would solve the world's woes in one small package. Sadly, it's not available in the US, according to Amazon anyway.

Kyhi, that first part in the PDF you sent seems the exact ticket. I'll try it in the morning and report back. It would solve a plethora of similar problems here.

@cereberus

Glad you mentioned the portable router -- I often use one of these for sharing NETFLIX / SKY SPORTS with colleagues in adjoining rooms when in hotel for business - or enabling group meetings -- usually hotels allow only 1 device or at most 2 -- but with one of these you create your own private network (Hotel Internet is usually good enough in the places I stay in to handle this).

Mines a DLINK AC750 DIR 510-L and can also be used to emergency re-charge a mobile phone too. Decent speed too for one of these - especially when connected to a decent 5GHZ wifi network or even a LAN port.

Cheers
jimbo