@pseudonymdk 

>Testing the speed using the Deco speed test (that is supposedly powered by speedtest.net),

There are three places in Deco app where one can run speed test. Which one have you used, is it "Test Internet Speed'" under More, in Router Settings screen, or some other? 

I was indeed using the test under "More". If it tested the speed form main deco to modem of my ISP, why is it not 1000/1000 when it's connected by a .5 m ethernet cable?

I tried the one under Lab, and it's even worse - 150 ms ping, 25 down, 68 up. This is on a sattelite Deco, a couple of rooms away. If I try on my Macbook here, I get 80/80. 

If I try the lab speed test when standing right besides the main deco, I get 10 ms, 33 down and 720 up.

_____

So outside of backhauling all the sattelites through ethernet, what can I do to improve the performance? I'd expect to have very close to 1000/1000 when standing right next to the main unit which is directly cabled to the ISP router?

 

@TP-Link 

No, thank you! :) I love that you can official and detailed support from the manufacturer themselves! 🙌

Unfortunately, I'm in the process of moving, and do not have a device with an ethernet port handy yet, perhaps sometime later this week. 

I have three components in the setup, 

1. The ISP box, where the fiber cable is run into
2. The WiFi router provided by the ISP
3. The Deco x60 system

alongside some different switches, the first amongst these (and the only one in use at the moment) being a TP Link TL-SG108. 

The current setup that provided the results so far is

ISP box -> WiFi Router -> Deco X60 main unit through ethernet cables (and some results from sattellite units connected wirelessly to main unit, but let's focus on the results from standing besides the main unit for now - my plan is to cable the sattelite units later on anyway)

I'm wondering whether going through the ISP's provided WiFi router is necessary, and maybe part of the problem? I remember trying to put the main Deco directly in front of the ISP box during setup, but it didn't work in the first try, so I set it up with the router in between to get it working quickly. I wrote to my ISP yesterday, though, and asked whether it was required to put their router first in the chain, and got a fairly detailed answer. I'll try to translate it almost directly here for context:

My question: "I bought a WiFi mesh system (Deco X60) to improve the WiFi coverage of my house. Do I need to put your provided router in front of the fiber box to get it to work, or can I run a cable from the box directly to a switch or the main unit in the wifi mesh system?"

The answer:

"If your mesh has a base that it runs from, you should be able to put it directly after the box, but it's not something we can help you with.

If you want to use your own router, there are two methods you can use. 
1. Bridge mode. You will put the router from us in bridemode, and then put your own router in one of the LAN ports on our router. This will make your own router the primary router, and ours will just forward all traffic. 
2. VLAN-tagging. Alternatively, you can VLAN tag your own router to 101. This will make it possible to connect your own router directly to the media converter. You can VLAN tag a router on it's config page. NB: Only some routers support VLAN tagging."

Based on the answer above, can you perhaps help me with the most optimal setup using the Deco X60's? :) Can the x60 skip their router (function as a "base"), or should I go through their router and set it in bridgemode or use VLAN tagging? If I should go with VLAN tagging, do you have a setup guide I can follow? I'm not too well versed in network tech :) 

Thanks again!