@Adam1V 

I'll answer your questions in their order. Answers:

1.  For Deco mesh in Access Point mode you should follow the 3rd picture. The 2nd picture is valid setup, too, but the 3rd picture will provide better Deco mesh performace and resilience. 

2. Hardwired Deco nodes will use Ethernet backhaul, as long as switch is compatible with Deco Ethernet backhaul protocol. If it is not, your Deco mesh will either be unstable or use WiFi backhaul.

3. You can connect PC or laptop to available Ethernet port of Deco node, and they will have Internet access. More to that, you can connect switch to Deco and through the switch connect more than one device to Deco node.

Also, recommendation: if you have Smart TV with Ethernet port, and Deco node nearby, consider connecting them by Ethernet cable.

4. In Access Point mode, with all Deco hardwired, location of Main Deco does not matter. Still, Main Deco must be hardwired to home network (anywhere, somewhere). You can't have Main Deco connected by WiFi.

5. Not really, there is not much more can be found on that topic than listed in FAQ you referred to (https://www.tp-link.com/uk/support/faq/1794)

6. It is recommended to disable loop protection, if switch supports it.

7. How do you know your Decos are not connected to the network? 

7a. What is the color of LED on Deco nodes: What do the different LED colors meaning of Deco?

7b. You can see in Deco app if and how Deco nodes are connected to the network. Example from my home network, with two Satellite Deco connected by Ethernet and one (Bedroom) by WiFi to Main Deco:

Hi @Alexandre,

Thank you very much for your quick response, it's really appreciated.

For #7, I meant to say when I left the house, none of them were physically connected. However, after just watching a few YouTube videos of the setup, it appears to ask the user to input their existing Wifi SSID and password - I think it may be bridge the connection perhaps? 

From 3:19 onwards (https://www.youtube.com/watch?v=o5USGecx9fY&ab_channel=SECUREACOM) this guy appears to be experiencing an unstable internet connection when plugging in a 2nd device, this is what I experienced earlier myself and couldnt get my head around it. Do you know why this might be?

All day, I've been experiencing very unstable nods, going Red, and its usually required me to unplug things.

Even directly connecting into the switch with my laptop, my internet has dropped which should have been a hardwired connection, and this matches the issues in the video link above.

From what I've found online, the HP Procurve 1810 does not support IEEE 1905.1, which might also be one of the issues.

One final question, the suggested TPLink switches which support IEE 1905.1 appear to be fairly inexpensive (1G 8 port), would it be possible to put one of these switches up front to pickup all the M4 connections with a single link back to the main Procurve switch or even the Main Deco, would this resolve the network imcompatability / storm?

  @Adam1V 

I briefly glanced at YouTube video: a guy with so much networking gear should know better than expect "everything just works" and complain when it does not. 

The switch he uses is from DLink, that brand is incompatible with Deco mesh Ethernet backhaul, and that explains everything.

I run my Deco mesh in Access Point mode, and it is rock solid. I use cheap 5-port and 8-port dumb gigabit switches, from TrendNET and TP-Link. 

If your switch is not Deco mesh compatible, you may need to replace it if you plan to stay with Deco. The obvious replacement is from TP-Link brand.

Also, disable loop detection, at least for ports to which Deco nodes are hardwired. 

Hi @Alexandre

I've just ordered TP-Link TL-SG108, which I think is one of the listed Ethernet switches on the Wiki pages. Hopefully that should resolve my issues and i'll report back on how I get on :)

  A quick update from me, with some fairly positive news.

I've walked away this evening with the network around 95% complete and up and running.

The existing Procurve switches do not support IEEE 1905.1, but the small TPLink switches I ordered did and they allowed the Decos to be connected as per the 3rd picture above.

A couple of issues I did run into:

1. Placing any other network switch in the mix, caused the system to fail / internet to drop out (i.e a non IEEE 1905.1 switch). I have a couple of connections I need to pickup with a Deco, so i'll grab another couple of switches.
2. I found when Plugging in a SkyQ box into the Deco, this similarly crashed the network, im not sure why, perhaps there is something going on within the Sky boxes, but I am wondering whether a TPLink switch between the Deco and Sky Box would solve this?
3. I wanted to locate a Deco directly next to my Modem Router and when I plugged one in (Zyxel model), this similarly crashed the system, again im wondering whether a TPLink switch between the two will resolve this?

Overall, the IEEE 1905.01 switch was a bit of a pain to work around, mainly due to my lack of knowledge and understanding, but more critically when the system crashed it took ages to recover or reboot.

Thanks for your help above, it's really been a big help.