Consumers - T25: First Time Installation

ARRIS Consumer Care


T25: First Time Installation

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How do I install the T25 Cable Modem for the first time?
When installing the T25 for the first time, it is required to activate the Modem for Internet access.  This document contains the following sections:
Prior to Installation
  1. Check that the following items were included with the T25 Cable Modem.  
    • Power Cord
    • Ethernet Cable
    • Quick Start Guide
    • Software License & Warranty Card
    • Support Information Card
  2. Turn off and unplug all existing routers and modems. 
  3. Establish cable service with Comcast by contacting 1-800-Xfinity (1-800-934-6489).
  4. Locate the required information to activate XFINITY Internet service.
    • Comcast Account Number
    • Phone Number
NOTE: The Comcast account number can be found on the billing statement, the Comcast app or the work order for the service.  Comcast account login credentials if it's previously created. 

  1. Connect the coaxial cable (not included) from the cable wall outlet or RF splitter to the Cable connector on the rear of the T25.  Tighten the connector by hand.
  2. Connect a telephone cable to the TEL LINE port on the phone and to the Tel1 port on the rear of the T25.

    NOTE: Contact Xfinity Consumer Support to activate the VoIP service.

  3. Connect the Ethernet cable to the Ethernet port on the rear of the T25 and the Ethernet port on the Wi-Fi router, PC, or laptop.
  4. Connect the power cord to the Power port of the rear of the T25, then plug it into an electrical wall outlet that is not controlled by a wall switch.

    NOTE: The T25 automatically powers ON when the power cord is connected.

    User-added image

  5. Check the front panel LEDs on the T25.  After a brief pause the Power, US/DS, and Online LEDs should light up SOLID white.

    User-added image

    LED IconBlinkingOn (Solid White)
    User-added imageNot applicable; LED does not blink.AC power is properly connected to the cable modem.
    User-added imageScanning for upstream (send data) and downstream (receive data) channel connection.Upstream and downstream channels are connected.
    User-added imageScanning for an Internet connection.Cable modem is connected to the network.
    User-added imageTelephone Line 1 is either off-hook or a call is in progress.Telephone service for Line 1 is connected and activated; on-hook.
    User-added imageTelephone Line 2 is either
    off-hook or a call is in progress.
    Telephone service for Line 2 is connected and activated; on-hook.
  6. The Modem is activated when the Online LED is solid white.

    NOTE: If activation is unsuccessful, contact Xfinity customer support for further assistance and provide the following information:
    • ​Modem Manufacturer
    • Model Number
    • Serial Number
    • HFC MAC ID
    • MTA MAC ID (applicable for voice service) 
    User-added image

  1. On your mobile device, download the Xfinity app from the App store or on Google Play.  If you already have the Xfinity app, make sure to update to the latest version.
  2. Open the app and sign in with your Xfinity ID.
  3. Follow the steps to get online.
  4. The front LEDs will be solid when it has reached this state.  The modem may reboot a few times during the activation process, which is normal.
  5. Activation is complete when there is solid white Internet LED.  It may take up to 10 minutes before you can connect to the Internet.
  6. Test the Internet connection by rebooting the computer and browse to



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