@El_Lobo 

 

Just because you have spare M5 around, I would like to suggest you try the following setup:

 

ISP Fiber router ====> Main Deco M5 =====> Satellite Deco M5 =====> Powered 8 port ethernet switch =====> (wired devices)

 

Add your spare M5 as Satellite Deco to your Deco mesh. Place Satellite Deco M5 where switch is, unplug Ethernet cable that connects Main Deco to switch from the switch and plug it to Satellite Deco, using another short Ethernet cable connect Satellite Deco M5 to switch.

 

What will this test?

 

1. The issue when Main Deco gets confused while it tries autosensing WAN/LAN Ethernet port;

 

2. The issue with Ethernet cable between Main Deco and switch. If something happened with that cable, such a cracked or what else, you now have simple way to figure that: during the Ethernet outage, if Main Deco M5 LED stays GREEN but Satellite Deco M5 goes RED, there is definitely something with the link between these two Deco, i.e., with the cable.

 

3. If wired Internet still goes down, but Deco M5 LED stays GREEN for both Main and Satellite, unplug switch from Satellite M5 and plug single wired device such as laptop or desktop to available Satellite Deco M5 Ethernet port. If device gains wired internet access, your suspect is now switch and whatever is connected to that switch.

 

Yes, I know, some symptoms don't match, but you can try that test to be sure. Also, if by some reason you'll get stable wired Internet with that setup I recommended, you now have time to figure what will be your next steps or what to check next.

  @Alexandre.

 

As I said in my original post.

• I know it is not the cable as I tried a new cable.
• I know it is not my powerd hub as I bypassed it and had the same problem 
• I had also replaced the Main deco with a spare (and set the spare as the Main) and that seemed to have no effect...other than messing with all my wi-fi security devices.

 

I will connect another Deco unit to the Main deco and then to the hub to see what happens with that.

 

Thanks.

  @El_Lobo 

 

One thing I forgot to mention: after you added Satellite M5, please verify in Deco app it established Ethernet link to Main Deco:

 

 

If/when you lose wired Internet again, check LED on both Satellite and Main Deco, and if it is green on both - also check if they are still linked by Ethernet, or now connected by WiFi:

 

 

 

  @Alexandre. 

 

So this is the only configuration I can make work.

 

 

ISP Fiber Router --------(cable)------->M5(Main) --------WIFI------->M5(Secondary)--------(cable)------->Ethernet Switch----Devices

 

I ran this configuration for a week and it was stable.  So I figured there must have been a problem with the Ethernet hardware on the Main M5. Then I swapped my Secondary and made it the Main, went back to my original configuration that had worked for years...and the problems started a few minutes later again with all my ethernet devices.

 

So now I am running this new configuration again where my Main and Secondary physical units have been swapped.  So I know if is NOT an Ethernet issue with the original (now Secondary) M5 unit.

 

I also tried

 

ISP Fiber Router --------(cable)------->M5(Main) --------(cable)------->M5(Secondary)--------(cable)------->Ethernet Switch----Devices

 

and this seems stable also. And I checked the source of the Secondary and it is Ethernet.

 

So when I try to connect the Ethernet Switch to the Main M5, it does not work...I have to use a secondary satellite unit...which is stupid and unacceptable.

 

Also, The 2 M5 Units are sitting 6" from each other so not optimal from a wifi signal perspective but it is the only thing that works.

 

So I am back to assuming the problem was in the last firmware update.

Just a quick note to say the ethernet bridge between the 2 Deco units became unstable so I am back to wi-fi between the 2 deco units and then ethernet to my switch from the secondary M5.