Your Deco mesh system does not have to plug directly into your modem, but one unit should connect to it
A Deco mesh system (TP-Link's home WiFi product) works by having one main unit — called the primary node or router — connect to your modem via ethernet cable. The other Deco units then connect wirelessly to that primary node and to each other, spreading WiFi throughout your home. You do not need to plug every Deco into the modem, only the first one.
The reason one unit must connect to the modem is straightforward: your modem is where your internet enters the house. That connection has to go somewhere, and the Deco system is designed to receive it through one wired link. Once that primary Deco has internet, it broadcasts WiFi, and the other Deco units pick up that signal and repeat it.
If you try to run a Deco system without any unit plugged into the modem, the system will have no internet to distribute, no matter how many units you have. Think of it like a water system: the main line comes from the street into one point in your house, and from there it branches out to the rest of the plumbing.
Key Takeaways
- One Deco unit must connect to your modem with an ethernet cable; the others connect wirelessly to that first unit.
- You can place the primary Deco anywhere in your home as long as the ethernet cable reaches from the modem, though central placement works better for signal strength.
- Additional Deco units need power outlets but no direct connection to the modem or to each other.
- If your modem and router are in different rooms, you can run a long ethernet cable or use a powerline adapter to bridge the distance.
Which Deco unit should connect to the modem
The Deco unit you designate as primary (the one that plugs into the modem) becomes the main router for your network. During setup, the Deco app will guide you through this choice. Most people make the unit closest to the modem the primary one, straightforward because the ethernet cable is shorter and easier to run.
However, you do not have to follow that rule. If your modem sits in a closet or corner, you can run the ethernet cable to a Deco unit in a more central location — like a hallway or living room — and make that the primary. The trade-off is a longer cable run, but the WiFi coverage will often be better because the primary node broadcasts from a better spot in your home.
Once you have chosen and set up the primary Deco, the other units (called satellite nodes) will automatically connect to it wirelessly. You just plug them in, and they join the network on their own during the initial setup process.
What happens if your modem and primary Deco are far apart
If your modem is in a basement or utility room and you want the primary Deco upstairs, a long ethernet cable is the straightforward solution. Ethernet cables can run 300 feet before signal degradation becomes a real problem, so most homes can manage this without trouble. Run the cable along baseboards, through walls, or under carpets (though under carpets is not ideal long-term).
If running a cable is not practical, a powerline adapter can help. This is a pair of small devices: one plugs into an outlet near the modem and connects to it via ethernet, and the other plugs into an outlet near where you want the primary Deco. The two communicate through your home's electrical wiring, carrying the internet signal. Powerline adapters are slower than a direct ethernet cable but faster than WiFi, and they work well for this purpose.
A third option is to use a WiFi extender or second router to bridge the gap, but this adds complexity and usually reduces speed. The ethernet cable or powerline adapter approach is simpler and more reliable.
Can you use WiFi instead of an ethernet cable for the primary Deco
Deco systems are designed to have the primary node wired to the modem. Some mesh systems support a "wireless backhaul" mode, where satellite nodes connect to the primary over WiFi instead of ethernet, but the primary itself still needs a wired connection to the modem to receive internet in the first place.
If you connect the primary Deco to the modem wirelessly (using the modem's WiFi), you are adding an extra step that slows everything down and defeats the purpose of having a mesh system. The primary Deco would be receiving a WiFi signal from the modem, then broadcasting its own WiFi to the satellites, which then broadcast to your devices — that is three layers of wireless, and each one loses speed.
For the best performance, keep the primary Deco wired to the modem with ethernet. This gives you a fast, stable connection from the modem to the mesh system, and then the Deco handles WiFi distribution from there.
Setting up the ethernet connection between modem and Deco
Most modems have one or more ethernet ports on the back. Plug one end of an ethernet cable into any available port on the modem, and the other end into the ethernet port on your primary Deco unit. Then plug the Deco into power.
The Deco will boot up and look for an internet connection. Once it finds one through the ethernet cable, it will start broadcasting WiFi. Open the Deco app on your phone, and it will walk you through naming your network, setting a password, and positioning the other Deco units. The app will also let you know when each satellite is connected and how strong its signal is.
If the Deco does not detect internet after a minute or two, check that the ethernet cable is fully seated in both the modem and the Deco. A loose connection is the most common reason for this step to fail. If the cable is find and it still does not work, restart the modem by unplugging it for 30 seconds, then plug it back in and wait for it to fully boot before checking the Deco again.
Do the satellite Deco units need ethernet cables too
No. Satellite Deco units connect to the primary Deco wirelessly, so they only need a power outlet. You do not plug them into the modem, and you do not need ethernet cables for them.
That said, if you have an ethernet cable available near a satellite unit and want maximum speed for a particular device (like a desktop computer or smart TV), you can plug that device into the satellite's ethernet port. Some Deco models have one ethernet port on each satellite for this reason. But it is not required — the satellite will work fine on WiFi alone.
Troubleshooting a Deco that will not connect to the modem
If your primary Deco is plugged into the modem but is not getting internet, start with the basics. Check that the ethernet cable is fully inserted into both devices — push it in until you hear or feel a click. Look at the lights on the modem and Deco; most modems show a light when they have an active ethernet connection, and most Deco units show a light when they detect internet.
If the lights look wrong, try a different ethernet cable. Cables can fail, and a bad cable is often the culprit. If you have a spare cable, swap it in and wait 30 seconds to see if the Deco connects.
If the cable is not the issue, restart both devices. Unplug the modem, wait 30 seconds, and plug it back in. Once the modem is fully booted (all lights stable), unplug the Deco, wait 10 seconds, and plug it back in. Give it another 30 seconds to detect the internet connection. If it still does not work, check the Deco app to see if it shows an error message — the app often provides clues about what is wrong.
Frequently Asked Questions
Can I plug multiple Deco units into the modem at the same time?
Technically, most modems have only one or two ethernet ports, so you may not have enough ports. More importantly, you should not do this — the Deco system is designed with one primary node connected to the modem and the rest connected wirelessly to that primary. Plugging multiple Deco units into the modem can cause conflicts and prevent the mesh from working correctly.
What if my modem does not have an ethernet port?
Most modems have at least one ethernet port, but if yours does not, contact your internet provider. They may be able to swap it for a model with ethernet, or they may recommend a separate router that does have ethernet. A Deco system cannot function without a wired connection to the modem.
Do I need to restart the modem when I add a new Deco satellite?
No. Once the primary Deco is set up and connected to the modem, you can add satellite units without restarting anything. Just plug in the new satellite, open the Deco app, and follow the prompts to add it to the network. It will connect wirelessly to the primary Deco.
Can I move the primary Deco to a different room after setup?
Yes, but you will need to move the ethernet cable with it. Unplug the ethernet from the old location, run it to the new location, and plug it back in. The Deco will reconnect to the modem and resume broadcasting. The satellite units will automatically reconnect to it wirelessly.
What is the maximum distance between the modem and primary Deco?
An ethernet cable can reliably carry a signal up to about 300 feet, though most homes do not need anywhere near that distance. If your modem and primary Deco are more than 100 feet apart, a powerline adapter is a good alternative to running a very long cable.