Nest Wifi Pro Won't Recognize Ethernet Connection (Backhaul Wiring)

[monodub]

Setup:

2 Google Nest Wifi Pros (Primary, Secondary).

GFiber jack LAN > Primary Nest WAN.

Primary Nest LAN > Unmanaged switch (TP Link TL-SG108)

Ethernet Port (functionality confirmed with other devices) > Secondary Nest WAN.

Secondary Nest - Connection Type: Wireless

Troubleshooting to date:

Power cycled GFiber jack, Primary Nest, Secondary Nest.

Removed Secondary nest from network and re-added (1) allowing wifi to connect first then connecting ethernet 2) re-added with ethernet already connected). 

[monodub]

Advanced network settings:

Use wifi protected access 3: off

Use 160 mhz channel for max performance on 5ghz: off

UPnP: on

IPv6: off

DNS Settings: automatic

WAN connection: DHCP

Device mode: Primary Nest - NAT, Secondary Nest - Bridge mode

[MichaelP]

Hello @monodub 

I would just double-check to make extra sure your switch does not include any "loop detection" or "loop prevention" features. Occasionally, even "unmanaged" switches have this enabled by default, and may even include a physical switch on the outside of the unit to disable it. From my quick research on your switch, it does sound like it may include loop detection/prevention, and from what I can tell, yours is one that has a physical switch to disable "loop prevention". Flip that to "off" (and maybe power cycle the switch to be sure), and as long as your cables are good, I'll bet this starts working. That said, the manual says "off" should be the default, but this is still where I would start – it needs to be off so Nest WiFi can be the root bridge in the spanning tree.

If you still have problems after disabling loop prevention in the switch, I test this out by connecting that to-be-wired secondary directly to the LAN port on the primary Nest WiFi Pro unit using a short, known-good Ethernet cable. Preferably cat 5e (not cat 6 or greater) just to avoid issues with cable stiffness causing outer pin connection issues. That may require moving that secondary into the same area as the primary temporarily. But, once booted up and connected that way, you should see it as "wired" in the Google Home app. Then, still using short, known-good Ethernet cables, introduce the switch into the equation and verify the secondary still shows as "wired". If that works as expected, I'd take a long hard look at the long-distance Ethernet cable run (or runs, depending on where that switch lives).

Basically, if it's not loop detection/prevention, then it's more likely a wire issue, and this procedure should help you narrow it down to the problematic connection. Generally speaking, this "just works" when connected – no Nest WiFi Pro settings changes required, and it sounds like you've followed all of the recommended guidelines.

[monodub]

Thanks for the reply, Michael. Can confirm physical "loop detection" switch is toggled to "off." I forgot to mention that I previously connected primary Nest (LAN) directly to secondary Nest (WAN), power cycled, and secondary Nest still indicated "wireless" connection. Can confirm I am using new cat6 connecting cables throughout, whereas ethernet runs are cat5e. All ethernet ports throughout house are functional when connected to other devices.

[MichaelP]

Ok, that's good debugging. I would start focusing on the Ethernet cables, then. Cat 6 cables are much stiffer than cat 5e (and unnecessary for the 1Gbps connections Nest WiFi Pro ports are capable of). The issue with that is, that stiffness can cause any lateral torque on the cable going into the Nest WiFi Pro port to have unreliable connections on the outer pins. Often this manifests as 100Mbps being negotiated, but it can cause the entire connection to fail as well. So, if you only have Cat 6 patch cables, I would just try to get them connected straight in with no side-to-side pressure on them if at all possible.

You can also try using the other port on the Nest WiFi Pro secondary unit. On a secondary, it's in bridge mode, so both Ethernet ports are connected to the same internal bridge, and wired backhaul works with either port (I personally like to pick one and stick to it, but while debugging, trying the other one won't hurt).

You could also try connecting a PC or laptop via Ethernet to the WAN and LAN Ethernet ports on that Nest WiFi Pro secondary while it's in wireless mode just to try to get some more clues about whether those ports are actually "good" or not.

If you can prove that one or the other of those ports really are bad, I'd try to get the unit replaced under warranty.

[monodub]

Secondary Nest (LAN and WAN) connected to laptop shows a wired connection - though I suspect this is really just feeding off of the Nest's wireless connection. Regardless, it demonstrates that the ports are functional. The cat6 cables being used are flat, quite pliable, and haven't shown to have any other connectivity issues. But I'll keep that possibility in mind. One additional piece of info: I had the ethernet cable connected to the secondary Nest over the weekend and spot checked the Google Home app to see if it'd ever show a "wired" connection (it did not). But it did show a "great connection" whereas it often shows a "weak connection" as the two points are separated by a floor/story. Also, when I unconnected the ethernet from the secondary Nest this morning, the indicator light flashed green and I had to power cycle it for it to reconnect. So it's almost as if the ethernet is connecting but failing to read as a "wired" connection. Is that a thing?

[MichaelP]

Yes, connecting a wired device to one or the other of those ports is just to test that they are working and that the patch cable is working with them – that's the only point of that exercise.

It sounds like your cat 6 cables are more pliable than they probably should be to meet the cat 6 spec (which has constraints on bend radius). But, in this case, that's a good thing, since it makes the torque / outer pin issue much less likely.

So, the "additional info" you provided is really interesting. It does sound like the wired backhaul is actually working just from the mesh test and behavior when disconnected. If so, that's good news, but puzzling since the app should show "wired" in that case – I've never heard of that happening before, but that doesn't mean it hasn't or that it isn't, and I don't have any Nest WiFi Pro units to test with here, unfortunately.

So, if you're seeing good benchmarks from devices connected to that secondary and everything is stable, I think I might call it good and ignore the indicator in the Google Home app. I'd probably "send feedback" in the app to report the discrepancy, though, just in case it's a regression they aren't aware of.