@TP-Link_Deco 

Thanks for the reply.  To reduce the interference from two same SSIDs then in my case (all 3 decos in AP mode), should I change the SSID of the deco and (even when in AP mode) and assign some devices to the deco SSID and some to my ISP router SSID?

@chumba 

If you want worry free network with Deco nodes in AP mode, you should turn off WiFi on your ISP router.

Here is how I added Deco mesh to my network:

1. Disabled WiFi on my ISP router. All WiFi connected devices disconnected (obviously). No other changes done to ISP router.

2. Connected Main Deco to ISP router with Ethernet cable and configured it with same SSID and password that ISP router had. Set Deco to run in AP mode.

3. Configured Satellite Decos.

4. Moved Satellite Decos to desired locations.

5. Meanwhile, all wireless devices seamlessly reconnected to Deco mesh.

As a result, ISP router still manages network and provides wired access Internet, Deco mesh provides WiFi. No conflicts or headaches whatsoever.

@Alexandre.  Thanks, when you say turn off wifi is that simply disabling the 2.4 and 5ghz wifi in the settings on my ISP router?  .. no need to put into bridge mode and/or ip passthrough?  I have the deco set up now as access points, with same ssid/password as the ISP router, running alongside one another.  Are you suggesting I simply log into the ISP router now and disable the wifi? 

Thanks so much!! 

@chumba 

This is correct: when you run Deco in Access Point mode all you need to do is log into the ISP router and disable WiFi in its settings.

To make sure we are talking the same thing when referring to Access Point mode, this is what Deco App should report under Operating Mode:

@Alexandre. 

Sounds simple enough to me! I just hope nothing weird happens when I disable wifi on the ISP router (hopefully all connected devices will auto learn to connect to the deco access point with same ssid/password). 

Well, I just disabled 2.4 and 5ghz wifi on my isp router..  now the 5ghz wifi seems to be missing on my devices (can't connect to 5ghz).  2.4ghz SSID is still fine and broadcasting.  I have 5ghz and 2.4ghz showing as enabled on my deco app.  The deco is in access point mode as described above.  Any ideas?

@Alexandre. I am going to proceed exactly this way.  I'm just lost on how you set up the main M4 when you previously disabled Router WIFI.  How the app "see" the M4?  Cheers, Sergio

@SioComani 

I am not totally sure about details, but I think Deco unit in configuration state creates its own temporary WiFi SSID, to which Deco app can connect for configuration.

By default, Deco starts in Router mode. Assuming you do not have any other WiFi router in your house and you create your home network from nothing, with Main Deco as router, Deco app must have some way to connect to Main Deco, right?