To connect a router to a modem, run an Ethernet cable from the modem's Ethernet port to the router's WAN port, which is usually labeled Internet and set apart by color. Power on the modem first, wait for its online light to turn solid, then power on the router and finish setup in the router's app or browser page.
Last updated September 29, 2026.
Key Takeaways
- One Ethernet cable does the job: modem Ethernet port to router WAN (Internet) port. A cable plugged into one of the router's numbered LAN ports instead is the most common reason a new router shows no internet.
- Order matters. Modem on first, online light solid, then the router. When you replace an old router on a cable modem, restart the modem so it recognizes the new one.
- Most current routers finish setup in a phone app in about ten minutes. Set your own WiFi name, WiFi password, and admin password before you connect the rest of the house.
- If your provider's box already has WiFi built in, it is a gateway (modem and router in one). Your own router can still go behind it, with the gateway switched to bridge mode.
What You Need Before You Start
The modem and the router do two different jobs. The modem talks to your internet provider over the line coming into your home. The router takes that one connection and shares it with every phone, laptop, and TV, over WiFi and through its wired ports. Our guide to the difference between a modem and a router goes deeper on that. For the hookup itself, gather these:
- A modem your provider approves. Xfinity and Spectrum have been removing older DOCSIS 3.0 models from their approved lists, so confirm yours is still listed before you build a network around it. A DOCSIS 3.1 modem is the safe choice on cable.
- A router. A refurbished router arrives factory reset, so it sets up the same way a new one does.
- One Ethernet cable. Cat 5e or Cat 6 covers any plan up to a gigabit. On a multi-gig plan, use Cat 6 or Cat 6a.
- Both power adapters, plus an outlet or surge protector with two open spots.
- Your phone, with the router maker's app installed if the router uses one (TP-Link Tether or Deco, Netgear Nighthawk or Orbi, ASUS Router, eero, Google Home).
Which Port Is Which
Nearly every setup problem comes down to a cable in the wrong port. Here is what you will find on the back of each box.
| Port | Found on | What it looks like | What plugs in |
|---|---|---|---|
| Coax | Cable modem | Round, threaded metal connector | The coax cable from the wall outlet |
| DSL | DSL modem | Small phone-style jack | The phone cord from the wall jack |
| Ethernet (LAN) | Modem | Wider jack, like an oversized phone jack | The Ethernet cable going to the router |
| WAN or Internet | Router | A single Ethernet jack set apart by color, a gap, or a globe icon | The Ethernet cable coming from the modem |
| LAN (1 to 4) | Router | A row of matching, numbered Ethernet jacks | Wired devices: computer, TV, game console |
Two exceptions are worth knowing. Some mesh systems, including eero and most TP-Link Deco models, use auto-sensing ports, so either jack works for the modem. And some modems have two Ethernet ports: use the faster one (often labeled 2.5G) and leave the second empty, since it only works if your provider assigns a second IP address.
How to Connect a Router to a Modem
These steps cover a separate modem and router on cable internet, the most common setup. Notes for DSL, fiber, and 5G home internet follow in the next section.
Connect the Modem to the Wall and Power It On
Screw the coax cable from the wall outlet onto the modem's coax port. Finger tight is enough; a wrench can damage the connector. Plug in the modem's power adapter and leave the router unplugged for now.
If the modem is new to your account, it has to be activated before it will pass internet. Xfinity handles this in the Xfinity app (see Xfinity's activation steps or our Xfinity modem activation guide). Other providers use their own app, an activation web page, or a phone call.
Wait for the Modem's Online Light
Give the modem two to five minutes. The Online light, sometimes shown as a globe icon, should stop blinking and stay solid. A modem on its first boot can take 10 to 15 minutes while it downloads firmware. If the light never settles, the problem sits between the modem and your provider, and no router setting will fix it. Our modem and router lights guide explains each color and blink pattern.
Run the Ethernet Cable From the Modem to the Router's WAN Port
Plug one end of the Ethernet cable into the modem's Ethernet port and the other end into the router's WAN or Internet port. Push until each end clicks. Keep the router's numbered LAN ports free for your wired devices.
Power On the Router
Plug in the router and give it one to two minutes to boot. Its internet light should turn solid white, green, or blue depending on the brand.
Replacing an old router? Do one extra thing. With the new router cabled in, unplug the modem's power for 30 seconds, plug it back in, wait for the online light, and then power on the router. A cable modem locks onto the first device it sees, and a restart makes it hand the connection to the new router.
Set Up the Router in Its App or Browser Page
- On your phone, join the router's default WiFi network. The network name and password are printed on the label on the bottom or back of the router.
- Open the router maker's app and follow the prompts. If the router has no app, open a browser and type the setup address from the label, commonly 192.168.1.1 or 192.168.0.1. Our router login guide lists the address for every major brand, and how to find your router's IP address covers the rest.
- Create an admin password when asked. Most routers made in the last several years have you set your own at first login instead of shipping with a shared default like admin/admin.
- Set your WiFi network name and a strong WiFi password, different from the admin password. Choose WPA3 security, or the WPA2/WPA3 mixed setting if you have older devices.
- Leave the internet connection type on Automatic (also called DHCP or Dynamic IP). That is correct for cable, most fiber, and 5G home internet.
- Turn on automatic firmware updates, or install any update the app offers.
If you are replacing a router, reuse the exact WiFi name and password from the old one and most of your devices will reconnect on their own. To change either one later, our WiFi password guide has the menu path for each brand.
Connect Your Devices and Test
Join the new network on a phone or laptop and load a website. Then run a speed test while standing near the router. A result close to the speed on your bill means the connection is good. Wired devices such as a desktop, TV, or game console plug into the router's numbered LAN ports.
Cable, DSL, Fiber, and 5G: What Changes
Cable Internet
Follow the steps above as written. Xfinity, Spectrum, Cox, Optimum, and Mediacom all work this way. Spectrum customers with the provider's own router can use our Spectrum router setup guide for the app steps.
DSL
A phone cord runs from the wall jack to the modem's DSL port in place of the coax cable. Everything after the modem is the same. Some DSL providers require a PPPoE username and password entered in the router before it will connect; your provider can supply them. Most DSL modems sold today are gateways with WiFi built in, so read the gateway section below before adding a second router.
Fiber
Fiber has no modem. A box called an ONT, usually mounted on a wall or in a utility closet, does that job, and your router's WAN port connects to the ONT's Ethernet port. AT&T Fiber is the exception: its gateway has to stay connected, so your own router plugs into one of the gateway's LAN ports and you turn on IP Passthrough.
5G Home Internet
The gateway from T-Mobile or Verizon is the modem. Plug your router's WAN port into the gateway's Ethernet port and set the router up as usual. Many 5G gateways have no bridge mode, which matters mainly for gaming and port forwarding. Our Double NAT vs. CGNAT guide explains what to expect.
Connecting Your Own Router to a Provider Gateway
If the box from your provider broadcasts WiFi, it is a gateway: a modem and a router in one case. Plugging your own router into it works right away for browsing and streaming. The catch is that two routers are now managing the same network, a condition called double NAT, which can cause trouble with online gaming, port forwarding, and some smart home devices.
The fix is bridge mode, a setting that turns off the gateway's router side and leaves it working as a plain modem. Our bridge mode guide has the steps for each major provider. Turn off the gateway's WiFi as well if bridge mode does not do it for you, so two networks are not competing in the same room.
The other route is to return the gateway and use your own modem with your own router. That removes the second router from the picture for good, and it ends the monthly equipment charge.
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Where to Put the Router
The modem has to sit near the wall outlet. The router does not have to sit next to the modem. The Ethernet cable between them can run up to 328 feet, so a longer cable lets you move the router to where the WiFi is needed. Put it out in the open, off the floor, and as close to the middle of the home as you can manage. Keep it away from microwaves, thick masonry walls, and large metal objects like a refrigerator or filing cabinet.
Setting up a mesh system instead of a single router? The main unit connects to the modem the same way, and the satellites go in afterward. Our Orbi setup guide walks through a full mesh install.
Router Connected to the Modem but No Internet
Work through these in order. Most setups are fixed by the first three.
- Check the port. The cable from the modem belongs in the router's WAN or Internet port, not a numbered LAN port.
- Check the modem's online light. Blinking or off means the modem has no service yet. Tighten the coax cable and give it a few more minutes before touching the router.
- Restart in order. Unplug both boxes. Plug in the modem, wait for a solid online light, then plug in the router. Our guide on how to restart your router has the full procedure.
- Confirm the modem is activated. A new modem that was never activated will show lights but pass no internet.
- Swap the Ethernet cable. A damaged cable can block the connection or hold speeds just under 100 Mbps on a faster plan.
- Check the connection type. It should be Automatic (DHCP) unless your provider gave you a PPPoE username and password.
- Factory reset the router as a last step. This erases its settings so you can run setup again from the start. See our router reset guide first.
If everything is connected and online but the WiFi falls short in parts of the house, the fix is a different piece of gear, and which one depends on the symptom.
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Frequently Asked Questions
Do I need both a modem and a router?
For WiFi and more than one device, yes. The modem brings the internet connection into your home and the router shares it. A gateway combines both in one box, and fiber service uses an ONT in place of a modem.
Which port on the router connects to the modem?
The WAN port, usually labeled Internet or WAN and set apart from the numbered ports by color or spacing. The numbered LAN ports are for computers, TVs, and game consoles.
Do I turn on the modem or the router first?
The modem. Wait until its online light is solid, which takes two to five minutes, and then power on the router. The router needs a working connection from the modem before it can share one.
Can I connect a router to a modem without an Ethernet cable?
No. The link between the modem and the main router is wired. Wireless connections begin at the router. If the two boxes need to sit in different rooms, use a longer Ethernet cable, up to 328 feet.
What Ethernet cable do I need between the modem and the router?
Cat 5e or Cat 6 for any plan up to 1 Gbps. For multi-gig plans, use Cat 6 or Cat 6a, and make sure both the modem's port and the router's WAN port are rated 2.5 Gbps or faster.
Can I connect two routers to one modem?
Not directly. A standard modem hands out one internet address, so only one router can use it. Plug the second router into a LAN port on the first and set it to access point mode, or use a mesh system for wider coverage.
Why does my new router say no internet?
The usual causes are the modem cable sitting in a LAN port instead of the WAN port, a modem that was not restarted after the router swap, or a modem that is not online or activated yet. Fix those in that order.
Do I need to call my internet provider when I get a new router?
No. Providers register the modem, not the router. A new router only needs a modem restart. A new modem does need to be activated through your provider's app, website, or phone line.
How long does it take to connect a router to a modem?
About 15 minutes: a few minutes for the modem to come online, a couple for the router to boot, and roughly ten in the app setting your WiFi name and passwords.
