@Malc34 

Hey

This is quite a common issue and its related to the operating mode of the Deco and not the new plugs you have purchased.

In short the Deco has 2 operating modes, ROUTER and ACCESS POINT mode. 

ROUTER mode is where there is one main deco connected to your ISP router, all the other decos connect to it wirelessly to create a mesh.  This is what you have been running for a while now.   In this mode the ports on the Deco nodes are for connecting devices to the internet, and NOT for connecting the deco devices together.   In short they service only clients and not backhaul traffic, therefore the Deco wont talk to each other over the Homeplugs you have added. 

To allow the ports on the Deco you would need to switch to ACCESS POINT mode, this would then allow the lan ports to be used for Deco to Deco connections (this is what you are after)

However Access Point mode is very different from router mode so will affect the setup of the whole network, namely you can no longer use any of the deco in MESH (connected wirelessly), therefore they will all need to be cabled in some way. 

More info here

https://www.tp-link.com/us/support/faq/1842/

  @Philbert 

Many thanks for that. Very helpful.

I previously had a BT Whole Home wifi mesh set up which only ran in AP mode. The router then had to do all the IP assignments. The router I had at that time could not cope with the growing number of smart devices we have (around 50 sometimes as my wife is disabled and uses voice command kit a lot).  So I changed to the Deco mesh system. Putting the Deco in Router mode and binning the original router meant that I reliably got most smart devices to work. 

However, despite adding 2 additional m9+ units, I struggle forming a reliable mesh in the workshop which is most remote fro the base.

For whatever reason the mesh often switches from what seems a logical piggyback connection to a more star like one viz

Preferred 'piggyback' map

(base1 to mesh 2 to mesh 3 (workshop) and

base1 to mesh 4 to mesh 5) which is logical given their locations

but it often connects as

Non preferred radial / star map 

base 1 to mesh 2, 

base 1 to mesh 3 (workshop being the furthest point away from base1)

and suaully base 1 to mesh 4 to mesh 5

If I could force the Deco to stay as the preferred map then the signal strength and speed in the workshop is good enough. It' is when it decides to swap over that the speed is very unreliable

Anyway I will return the powerline devices as they are clearly not going to help me. I hadn't really thought this through until your comments @Philbert so thx.

And I will go back to seeing if I can improve the Deco mesh somehow

Philbert wrote

  @Malc34 

 

However Access Point mode is very different from router mode so will affect the setup of the whole network, namely you can no longer use any of the deco in MESH (connected wirelessly), therefore they will all need to be cabled in some way. 

 

More info here

 

https://www.tp-link.com/us/support/faq/1842/

  @Malc34 

Hey

Rattling my brain here to find a way around this for you, so far all i have is

1.  A cheap good router, something like the ER605 (business grade device) to do the DHCP, and switch the Deco to Access Point Mode

2.  Split the Deco into 2 networks, one Router Mesh, other wired Access Point.   Same SSID and Password on both, have just the one Node you want on the Acess Point Deco setup, cabled back to the Mesh..  you would lose roaming between those two nodes.. but might solve the issue of signal!    The node in Access Point mode will pull a DHCP from the cable on the nearest Mesh node, the Mesh node will just see it as a client device (in theory anyways)

  @Philbert 

cheers

option 2 is worth a go

just ordered a long  cable to to do a test run!

  @Malc34 

Fingers crossed!!