I have two Nest Wifi Routers. I have connected them using wired Ethernet as follows.
(✓) Modem → Google Nest Wifi router or primary Wifi point → Switch → Google Nest Wifi router or Google Wifi point
This is a supported configuration per this document https://support.google.com/googlenest/answer/7215624?hl=en#zippy=%2Cinclude-a-switch-downstream-of-t...
My issue is that the secondary Nest wifi (i.e. the mesh one) doesn't seem to be using the Ethernet connection, instead it seems to be connected using Wifi to the primary router. The location for the secondary point has pretty bad wifi coverage (which is why I want to connect using the ethernet backhaul). So how would I configure this properly? I can't see any information in the Google Home app to set this up properly.
You shouldn't need to configure anything as long as the Ethernet connection is working properly. To check the status, in the Google Home app, tap the "Wi-Fi" bubble at the top of the home screen, then tap the "Wifi devices (#)" bubble, then tap the name of the secondary Nest WiFi Router unit, and finally tap the little gear icon in the upper right corner.
In the "Wi-Fi information" section there should be a "Connection type: Wired" if it's working properly via Ethernet. If it says "Connection type: Mesh" then it may not have a good Ethernet connection (but, sometimes it seems like that doesn't update right away, so close that window and bring it up again just to refresh it in case that's happening for you).
If it consistently shows "Mesh" in there, then you'll need to test the Ethernet connection using a laptop or something before connecting it again to the secondary Nest WiFi Router (I usually use the WAN Ethernet port on secondaries for consistency). If you have a more complex network of switches in between, then I would test that one piece at a time to be sure you have a known-good Ethernet connection all the way out to where your secondary is.
Thanks MichaelP for your response. It turned out to be STP as you have mentioned in your other answers. I turned off STP on my switch and it started using Wired connection for back haul. The Google home app now shows connection as 'Wired'.
So again thank you for the your help, as it was your other answers which lead me to STP. So I really appreciate it.
I hope Google would make a note on their help doc about so that its easier to debug.
TLDR; for others facing same issues. If you have a managed switch then you need to disable STP (or make sure your switch's priority is lower then Google Nest Wifi routers).
D'oh! I usually try to mention the risk of using managed switches, and I wish I had this time, since it's the most common issue after the cabling itself. I'm really glad you figured it out, though!
I'm glad to see that you were able to work this out. Thanks for letting us know what worked for you. Also, thanks to MichaelP for his help on the matter.
As we have our resolution here, I'm going to go ahead and close up the thread. If we have any other questions or needs, let's go ahead and start up a new thread.