Consumers - SB8200: Troubleshooting Internet Connectivity

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SB8200: Troubleshooting Internet Connectivity

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How do I troubleshoot Internet connection issues with my SB8200 cable modem?
If Internet connection issues with the SB8200 cable modem arise, troubleshooting may resolve the issue or may provide insight as to what is causing the issue.  This document provides helpful information for troubleshooting Internet connection issues with the SB8200 cable modem.

The following troubleshooting steps must be followed in sequence.

NOTE: If the solutions provided in this document do not resolve the issue, please contact the cable operator for assistance.

Check the Physical Connection
  1. Verify that the power cord is connected from the power port of the SB8200 cable modem to the power outlet.
  2. Verify that the coaxial cable is connected from the cable port of the SB8200 cable modem to the cable outlet.
  3. Verify that the Ethernet cable is connected from Ethernet port 1 on the SB8200 cable modem to the Ethernet port on the computer or Wi-Fi router.

    NOTE 1: A typical setup for Internet access consist of connecting one computer or a Wi-Fi router directly to the cable modem.  Connecting a Wi-Fi router to the SB8200 is recommended when there are multiple client devices in the home network.

    NOTE 2: It is possible to connect two devices to the SB8200.  However, the cable provider must provide Internet IP Address to each device for Internet access.  If both devices cannot connect to the Internet, contact the cable provider to request an additional Internet IP address.

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Verify the LEDs

With the proper setup, the Online LED should be solid green.  If this is not the behavior that the SB8200 cable modem is displaying, please refer to this table for more information regarding LED behavior.

NOTE: If the Receive, Send, and Online LEDs are flashing the modem may not be provisioned.  Please confirm with the service provider to ensure the modem is provisioned and have the HFC MAC address ready if requested. 

LED IconStatusIf, During Startup:If, During Normal Operation
User-added imageOffSB8200 is not properly plugged into the electrical outletSB8200 is unplugged
User-added imageFlashingDownstream receive channel cannot be acquiredDownstream channel is lost
User-added imageFlashingUpstream send channel cannot be acquiredUpstream channel is lost
User-added imageFlashingIP registration is unsuccessfulIP registration is lost

Verify If Any Clients Has Internet Access
  1. Make sure that the clients without Internet are connected to the SB8200 cable modem with an Ethernet cable or connected to a router's Wi-Fi SSID or Ethernet connection. 
  2. If there are multiple clients on the network, confirm if any clients can access the Internet.
  3. If a client can access the Internet, the SB8200 cablle modem is connected to the Internet and troubleshooting is needed on the client without Internet.
  4. Browse to to test the Internet connection.

Rebooting the Modem

Rebooting the modem allows the SB8200 cable modem to update and optimize the connection and speed, all while retaining the saved settings.  Rebooting is one of the easiest ways to resolve any connection issues.
  1. Shutdown the computer.
  2. Unplug the cable modem from the AC wall outlet and wait one minute.
  3. Plug the cable modem into the wall outlet.

    NOTE: There may be up to one minute delay for the Power LED on the SB8200 cable modem front panel to light up after the modem starts up.

  4. Wait until the Power, Receive, Send, and Online LEDs are solid.
  5. Restart the computer.

Factory Reset With the Reset Button

Resetting the SB8200 cable modem can fix connectivity issues and ensure it is operating at the fastest speed available for the Internet service subscribed.
  1. If there is no Internet access resetting the SB8200 cable modem to factory default can fix connectivity issue. 
  2. Carefully insert the tip of a pen or the end of an unwound paperclip into the reset button.
  3. Press and hold down the Reset button for 10 seconds and then release it.  The front panel LEDs will flash.

    NOTE: There may be up to one minute delay for the Power LED on the SB8200 front panel to light up after the modem starts up.

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Verify the Cable Signal Levels

All DOCSIS cable modems require that the cable signals fall within a very specific range to be an acceptable level for the modem to operate properly.  The following three cable signal levels must be within the acceptable ranges for the SB8200 modem to operate properly.

NOTE: If the SB8200 is connected to a router, it is recommended to disconnect the router and connect the SB8200 directly to a computer with an Ethernet cable.
  1. Launch a web browser, such as Internet Explorer, Firefox, or Safari.  Enter into the address box and press the Enter key.  The Login page will appear.

    NOTE 1: A security or private risk alert may appear on the web browser advising users to proceed with caution when accessing the Web Manager.  There is no risk in proceeding to the Web Manager. For instructions to by-pass the alert screen, refer to article # 18181 - Alert Message for Web Manager Access.

    NOTE 2: The admin login is not available on firmware version prior to and the Connection page will appear.
  2. On the Login page, enter admin in the Username field.
  3. Enter password or the last 8 digit of the serial number located on the bottom white sticker in the Password field.

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  4. Click the Login button.  The Connection page will appear. 

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  5. In the Downstream Bonded Channels section, verify Power levels are within the acceptable range of - 15 dBmV to + 15 dBmV for each downstream channel. 

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  6. In the Downstream Bonded Channels section, identify the Modulation and Power to find verify SNR levels are within the acceptable range for each downstream channel. 
    Downstream Signal To Noise Ratio (SNR)
    ModulationPowerAcceptable SNR
    QAM64-15 to 15 dBmV23.5 dB or greater
    QAM256-6 to 15 dBmv30 dB or greater
    -15 to -6 dBmV33 dB or greater
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  7. In the Upstream Bonded Channels section, identify the number of Channels and Type to find verify Upstream Power levels are within the acceptable range for each upstream channel. 
    Upstream Transmit Power Level
    ChannelUS Channel TypeAcceptable Upstream Power Level
    SingleSC-QAM45 to 61 dBmV
    TwoSC-QAM45 to 54 dBmV
    Three or moreSC-QAM45 to 51 dBmV
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  8. Refresh the page at least twice to identify variations in SNR, Downstream Power, and Upstream Power.   

    NOTE: If the either of the signal levels are outside of the acceptable range, power cycle or factory reset the modem. 

  9. Contact the cable provider to adjust the signal level to the acceptable level range. 



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