- You can activate most Xfinity-compatible modems yourself in about 15 minutes using the Xfinity activation website or the Xfinity app.
- Before you start, make sure your modem is on Xfinity's approved device list and that your coaxial cable connection is secure.
- If you need Xfinity Voice (phone service), you will need a telephony modem and must call Comcast to complete activation.
How to Activate a Modem With Comcast Xfinity
If you just bought your own cable modem and want to use it with Comcast Xfinity internet, you will need to activate it on the Xfinity network before it will work. The good news is that Xfinity makes self-activation fairly straightforward. This guide walks you through every step, including what to do if you also need phone service.
Before You Start: What You Need
Gather the following before you begin the activation process:
- Your Xfinity account number - Found on your bill or in your Xfinity account online.
- Your modem's MAC address and serial number - Printed on a sticker on the bottom or back of the modem. The MAC address is sometimes labeled "CM MAC" or "HFC MAC."
- A coaxial cable - This is the threaded cable that screws into the back of the modem and connects to the cable outlet on your wall.
- A power cord - The one that came with your modem.
- A phone, tablet, or computer - You will need a device to access the activation page.
Check Modem Compatibility First
Xfinity only works with approved modems. Before going any further, visit the Xfinity Device Compatibility page and enter your address. This tool will confirm whether your specific modem model is supported on your plan. If your modem is not on the list, it will not activate.
How to Activate Your Xfinity Modem Online (Self-Activation)
This is the fastest and most common method. Most customers can complete activation this way without calling Comcast.
Step 1: Disconnect Your Old Modem
If you are replacing an existing modem or returning a rented Xfinity gateway, unplug its power cord and disconnect the coaxial cable from the back of the old device.
Step 2: Connect Your New Modem
Screw the coaxial cable into the coax port on the back of your new modem. Make sure the connection is finger-tight. Then plug the modem's power cord into a wall outlet. Do not connect an ethernet cable to a router or computer yet.
Step 3: Wait for the Modem to Power Up
Give the modem about two minutes to fully boot. Most modems will cycle through several blinking lights. Wait until the "Online" or "Internet" light is either solid or blinking steadily. This means the modem is detecting the Xfinity signal.
Step 4: Go to the Xfinity Activation Page
On a phone or tablet using cellular data (not Wi-Fi, since your internet is not working yet), open a browser and go to xfinity.com/activate. Sign in with your Xfinity account credentials.
Step 5: Enter Your Modem Details
The activation page will ask for the CM MAC address or serial number from the sticker on your modem. Enter it carefully. The system will identify your modem model and confirm compatibility.
Step 6: Confirm and Wait for Activation
Follow the on-screen prompts to confirm your address and plan details. Xfinity will then send a signal to provision your modem. This process typically takes between 5 and 15 minutes. Your modem will likely reboot once or twice during this time. Do not unplug it.
Step 7: Test Your Connection
Once the modem's lights stabilize and the "Online" light is solid, connect an ethernet cable from the modem to your computer or plug your router into the modem. Open a web browser and try loading a website. If the page loads, your modem is active.
How to Activate Using the Xfinity App
If you prefer using your phone, you can also activate through the Xfinity app. Download the Xfinity app from the App Store or Google Play, sign in to your account, and look for the option to activate or manage your devices. The app will walk you through the same steps listed above, including scanning the modem's QR code or entering the MAC address manually.
How to Activate by Calling Comcast
If the online process does not work or you run into an error, you can call Xfinity customer support at 1-800-XFINITY (1-800-934-6489). Have your account number and modem MAC address ready. A representative will provision the modem remotely. This call usually takes about 10 to 20 minutes.
How to Activate a Phone Modem With Xfinity Voice
If you subscribe to Xfinity Voice (home phone service), you need a telephony modem, sometimes called a phone modem or eMTA. This is a modem that has both a coaxial connection for internet and one or two phone jacks (usually labeled "Tel 1" and "Tel 2") on the back for your home phone line.
Step 1: Connect the Phone Modem
Connect the coaxial cable and power cord just like a regular modem. Then connect your home phone to the "Tel 1" port on the back of the modem using a standard telephone cord.
Step 2: Wait for the Modem to Boot
Let the modem power up fully. Wait until the "Online" light and the "Tel 1" or "Phone" light begin to show activity. This may take a few minutes.
Step 3: Call Xfinity to Activate
Call 1-800-XFINITY (1-800-934-6489) and tell the representative you need to activate a telephony modem for internet and voice service. Provide your account number, the modem's CM MAC address, and the modem's MTA MAC address. The MTA MAC is a second MAC address found on the modem sticker, usually labeled "MTA MAC" or "eMTA MAC." The representative will provision both the data and voice sides of the modem.
Step 4: Test Your Phone and Internet
Once the representative confirms activation is complete, test your internet connection by loading a website. Then pick up your phone and listen for a dial tone. Try making a call to verify the voice service is working.
Troubleshooting Common Activation Issues
If your modem is not activating, try these fixes before calling Comcast:
Modem Not Detected
Make sure the coaxial cable is securely connected at both ends, the wall outlet and the modem. Try a different coaxial cable if you have one. Also confirm the cable outlet in your home is active. If you just moved in, Comcast may need to send a technician to activate the outlet.
MAC Address Not Accepted
Double-check that you are entering the CM MAC address, not the Wi-Fi MAC or serial number. If the activation page says the MAC address is already in use, it may still be tied to another account. You will need to call Xfinity to have them clear it from the previous account.
Modem Stuck on Blinking Lights
Unplug the modem from power, wait 30 seconds, and plug it back in. Let it go through the full boot cycle again. If the "Online" light never goes solid after 10 minutes, the modem may not be compatible with your plan or there may be a signal issue at your address.
Internet Works but Speed Is Wrong
After activation, run a speed test at speedtest.net. If your speeds are significantly lower than what your plan promises, your modem may not support the speed tier you are paying for. Check the modem's maximum DOCSIS speed rating and the number of channels it supports against your plan requirements.
Do Not Forget to Return Your Old Rented Equipment
If you were renting a modem or gateway from Xfinity, return it to an Xfinity retail store or ship it back using a prepaid return kit. Xfinity will continue charging you a monthly rental fee until the equipment is returned. Keep your return receipt as proof.
FAQ
Can I use my own modem with Comcast Xfinity?
Yes. Comcast allows customers to use their own modem instead of renting one. Your modem must be on Xfinity's approved device list for your plan and speed tier. Using your own modem saves you the monthly equipment rental fee.
How long does it take to activate a modem with Xfinity?
Online self-activation usually takes between 5 and 15 minutes after you submit your modem information. Activation by phone typically takes 10 to 20 minutes including hold time. In some cases, full provisioning can take up to an hour.
What is the difference between a cable modem and a phone modem?
A standard cable modem provides internet service only. A phone modem, also called a telephony modem or eMTA, provides both internet and home phone service. It has phone jacks on the back for connecting a landline phone in addition to the standard coaxial and ethernet ports.
Do I need to call Comcast to activate my modem?
For internet-only modems, you can usually self-activate online at xfinity.com/activate or through the Xfinity app. If you have Xfinity Voice (phone service), you must call Comcast at 1-800-934-6489 because voice provisioning cannot be completed through self-activation.
Why is my Xfinity modem not activating?
The most common reasons are an incorrect MAC address entry, a loose coaxial cable connection, an incompatible modem, or a cable outlet that is not active. Try re-entering the MAC address, tightening all cable connections, and verifying your modem is on the Xfinity approved list. If none of that works, call Xfinity support.
Can I activate an Xfinity modem at a new address before my move-in date?
No. The modem can only be activated once your Xfinity service is active at the new address. You can schedule your service transfer or new installation ahead of time through your Xfinity account, and then activate the modem on or after the service start date.
What does the Xfinity modem rental fee cost and how do I stop paying it?
Xfinity charges a monthly gateway rental fee that varies by region but is typically around $14 to $15 per month. To stop paying it, purchase your own compatible modem and router, activate the modem on your account, then return the rented equipment to an Xfinity store. The rental charge will be removed from your next billing cycle after the return is processed.
