[Stephank]

Update: I received my 3 pack mesh. installed the phone app for setup. Followed the instructions. The app knew the connection type "Dynamic IP' right away. When I set up the remaning 2 nodes, I stayed in the same room where T-Mobile gateway is. (Some Amazon reviewer recommended that.). It was easy. Placed one on the first floor and the last in the basement.
I used Ookla's speed test on iphone and chromebook in different parts of the house. My speed (with Deco) increased tremendously. I dediced to use the first node (attached to T-Mo's gateway) as a router.
Happy camper here.

 

[Stephank]

Got it. Thanks a lot. Now, the picture is getting clearer. I appreciate your time.

Regarding the word 'gateway' I meant the original t-Mobile combo. To me, deco is just a router.

 

[Stephank]

Let me see If I understand you clearly. I am an old geezer who is not at your level. (Liz, you are an exception!!)
If I keep the same gateway network name and password and use the mesh system as access point why is it necessary to disable wifi on gateway? The first node (mesh unit) is not working as a router. (I realize a lot of features that mesh system offer will be disabled, But, I will never need them for my needs.)
I am assuming that all the current IP addresses for about 19 devices I currently use will stay the same and mesh will simply give me a better wifi coverage all over the house, which has 3 floors including basement and about 2700 square feet.
The picture shows the options for Deco S4 operating mode.

 

[Stephank]

Yes. Turn off the wireless function on the T-Mobile gateway. The TP-Link will provide better overall wireless performance.

Port forwarding is essentially punching a hole in your firewall to allow inbound network traffic from the Internet. This is commonly needed when you do online gaming.

You indicated there is an option to use the TP-Link as only a mesh wireless AP system. This would be preferable as it removes the router/firewall function of the TP-Link and hands that off to the T-Mobile gateway. This simplifies configuration and management of your network.

Yes Deco S4 manual gives both options. Router capability and access point.
Here's my question. When I set up mesh system, should I enter the same network name and password (that I am currently using with gateway)?
Would Deco units would accept the same information? Of course, I will select 'Access point' during setup.

 

[Stephank]

Miracles happen! I tried to call t-mobile customer service and waited only 10 minutes.
The rep said it uses Dynamic IP.
I don't know what port forwarding means. I need some internet search. Basically, I want the signal coming from gateway to mesh units not degrade too much. I am thinking if I connect my laptop in my basement to one satellite with ethernet cable I will get a better download speed with big files.

 

[Stephank]

thanks. i will need to connect one of the nodes to gateway with ethernet cable, gateway has two ethernet ports in the back. each node also offers 2 ethernet ports. Dynamic IP would be my guess,too. I have an option to use that first node (attached to gateway)as a router, or use all 3 as access points. The concern is if two routers (gateway and that first router) will cause wireless interference. Some are saying you can turn off wifi on router and use a dedicated router, and some insist that not possible. Confusing.
what is your recommendation? Just use mesh nodes as access points?