Connect the modem to power and your internet line first

Your Xfinity modem needs two things to work: power and a connection to the cable line that runs into your home. Start by locating the coaxial cable — the thick cable with a threaded connector on each end — that comes from your wall or outside. Screw this cable firmly into the port on the back of the modem labeled "Cable In" or "Coax In". Do not force it; hand-tight is enough.

Next, plug the power adapter into the modem's power port on the back, then plug the adapter into a wall outlet or power strip. The modem will take 2 to 3 minutes to fully start up. You will see lights on the front turn on and change color as it boots. Wait until the lights stop changing before moving to the next step.

Key Takeaways

  • The coaxial cable from your wall connects to the "Cable In" port; the power adapter plugs into the power port on the back of the modem.
  • After powering on, wait 2 to 3 minutes for the modem to fully start — the lights on the front will stop changing when it is ready.
  • Once the modem is online, your router connects to the modem's ethernet port with a standard network cable.
  • If the lights stay red or do not light up after 5 minutes, restart the modem by unplugging it for 30 seconds, then plug it back in.

Check that the modem has connected to Xfinity's network

Look at the lights on the front of the modem. You should see a solid green light next to "Online" or a light labeled "Internet" that is steady green. If you see red lights, a blinking light, or no lights at all after 5 minutes, the modem has not connected yet. Unplug the power adapter, wait 30 seconds, and plug it back in. This restart usually fixes connection problems.

If the lights are still not green after another 5 minutes, check that the coaxial cable is screwed in tightly at both the wall and the modem. A loose connection is the most common reason a modem will not come online. If the cable is tight and the lights are still not green, the cable line itself may be down in your area — contact Xfinity support to check.

Connect your router to the modem with an ethernet cable

Once the modem shows a solid green online light, take a standard ethernet cable (the cable with rectangular connectors on each end) and plug one end into any of the ethernet ports on the back of the modem. These ports are usually labeled 1, 2, 3, or 4. Plug the other end of the cable into the "Internet In" or "WAN" port on the back of your router — this port is usually a different color from the other ethernet ports and is often labeled separately.

The router will take another 1 to 2 minutes to connect to the modem and start broadcasting your wireless network. You do not need to restart anything; just wait and watch the lights on the router. Once the router's lights stabilize, your network is ready to use.

Find your network name and password to connect devices

Your Xfinity modem and router come with a default network name (called an SSID) and password printed on a sticker on the device itself. Look on the back or bottom of the modem and router for a label that shows "Network Name" or "SSID" and "Password" or "WiFi Password". Write these down or take a photo.

On your phone, tablet, or computer, go to Settings and look for WiFi or Network options. Select your network name from the list of available networks, then enter the password exactly as it appears on the sticker — passwords are case-sensitive, so capital letters and lowercase letters matter. Once you enter the password correctly, your device will connect to the internet.

What to do if your devices will not connect to the network

If you typed the password correctly but your device still will not connect, restart the router by unplugging it for 30 seconds and plugging it back in. While the router restarts, also restart the device you are trying to connect — turn it off completely, wait 10 seconds, and turn it back on. After both devices have restarted, try connecting again.

If the problem continues, forget the network on your device and reconnect. On most phones and computers, you can do this by going to WiFi settings, selecting your network name, and choosing "Forget" or "Remove". Then search for the network again and re-enter the password. This clears out any corrupted connection data and usually solves the problem.

Change your default password to something you will remember

The password printed on your modem is long and hard to remember. You can change it to something easier through the modem's settings page. Open a web browser on any device connected to your network and type 192.168.0.1 into the address bar, then press Enter. A login page will appear.

Log in with the username "admin" and the password printed on your modem's sticker. Once you are logged in, look for a section called "WiFi" or "Wireless" settings. Find the field that says "Password" or "WiFi Password" and replace it with a new password of your choice — make it at least 8 characters long and include a mix of letters and numbers. Save your changes. Your devices will need to reconnect using the new password.

Restart your modem and router if the internet stops working

If your internet suddenly stops working even though the lights were green a moment ago, a restart usually fixes it. Unplug the power adapter from the modem first and wait 30 seconds. Plug it back in and wait for the online light to turn solid green again. Then unplug the router, wait 30 seconds, and plug it back in.

This process takes about 5 minutes total. Most internet problems — slow speeds, devices dropping off the network, pages not loading — clear up after a restart. If the problem comes back within a few hours, contact Xfinity support, as it may indicate a problem with the cable line or your account.

Frequently Asked Questions

Do I need a router if I have an Xfinity modem?

No, the modem alone will not broadcast a wireless network. You need a separate router connected to the modem to use WiFi on phones and tablets. If you only use one device with an ethernet cable plugged directly into the modem, you do not need a router.

What if I have an Xfinity modem and router combo unit?

Some Xfinity packages include a combo unit that has both the modem and router built in. You still connect the coaxial cable to the "Cable In" port and plug in power. The device will broadcast WiFi automatically once it comes online — you do not need a separate router.

Can I use my own router instead of the one Xfinity provides?

Yes. Any standard WiFi router will work with an Xfinity modem. Connect your router to the modem's ethernet port the same way described above. You can then set up your own network name and password through the router's settings page instead of using the default ones.

Why are there lights on the modem if it is already online?

The lights show you what the modem is doing at any moment. A solid green light means it is connected and working. A blinking light means it is sending or receiving data. Red or orange lights mean there is a problem. Learning what each light means helps you troubleshoot quickly if something goes wrong.

How do I know if the coaxial cable is screwed in tight enough?

Turn the cable connector by hand until it stops — you should feel slight resistance. Do not use a wrench or pliers; hand-tight is correct. If it is too loose, the modem will not connect. If it is too tight, you can damage the connector and the port.