Ethernet not working with unmanaged switches

[bessie31]

Hi everyone,

Over the past week or so, I started having issues with my ethernet-connected devices. First, I would start getting random notifications from my various smarthome hubs (Smarthings, Yale, Arlo, etc.) that they are coming offline. The common thing is that they are all using a wired connection through a switch. Finally, my work PC that is also ethernet connected started randomly dropping connections. By the end of the week, all the ethernet devices completely stopped working. One of my mesh nodes is also wired, and it also stopped working.

After basic troubleshooting I decided to first try to replace the switch, thinking it had failed. I purchased a new one, this time a different brand (still unmanaged), and it STILL did not work.

I returned that one, and bought the only other one available locally (another TP-Link SG108 just like the original one) and predictably, it still is not working. I tried a static IP, thinking there is a DHCP failure, but no luck.

FInally, I tried to connect a PC directly to the ethernet port on the "mother" router and it works fine. Therefore, the problem MUST be the unmanaged switches.

Anyone else having this problem appear out of the blue? Did Google release new firmware that broke some hidden loopback compatibility or something of that nature? Both Netgear GS108 and TP-Link SG108 are not working in my topography.

[MichaelP]

Hello @bessie31 

It can be really hard to know what's going wrong here. But, my money is on a bad cable somewhere in your system. Recent Google WiFi firmware updates have not broken this functionality.

You said you connected a PC directly to the primary/router unit's LAN port, and it worked fine. Did you use the same cable that was feeding your switch for that test?

I would probably break the system down into the simplest configuration possible and build things up one piece at a time. For example, you've disconnected the switch from your primary/router unit's LAN port, and a PC works through that port directly. Test that with the same cable used to connect to the switch. Then, disconnect all of the other cables from that switch and reconnect only the cable between the switch and primary/router unit's LAN port. Make sure the lights on the switch show a good 1Gbps link connection (if it has lights). Then, connect a computer directly to one of the switch ports using a short, known-good cable and test it. If that works, start reconnecting one other cable at a time and testing again. If things take awhile to "go bad", then leave it in each intermediate state long enough to know whether it's really working or not.

Yes, this can be tedious and time-consuming. But, it's really the only way to isolate the problem. You may find another piece of equipment on your network has been updated to interact poorly with Google WiFi. I think that's unlikely, but not impossible.

Another thing I've seen go wrong is USB Ethernet adapters for computers can start spraying packets into the Ethernet network when the computer they are connected to is powered off or asleep. they can even do this if they are connected to a hub of some kind and the computer is disconnected from the hub. Just mentioning this possibility in case it might apply.