How to Troubleshoot a Motorola SBV5121 Cable Modem

Written by jedadiah casey
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How to Troubleshoot a Motorola SBV5121 Cable Modem
(cable modem image by IKO from

The Motorola SBV5121 cable modem acts as a gateway between the local area network (LAN) and the Internet. A Motorola cable modem is preconfigured by your cable Internet service provider (ISP) to connect to its network and receive a public IP address. Sometimes, due to misconfigurations on the user side or the ISP side, the Internet connection does not work and needs troubleshooting. By following a few simple steps, the cable Internet connection can be back up and running with minimal effort.

Skill level:


  1. 1

    Unplug the power from the cable modem.

  2. 2

    Unplug the power from a connected router, if present.

  3. 3

    Reinsert the power connector to the cable modem and wait approximately two minutes.

  4. 4

    Reinsert the power connector into the router, if applicable, and wait approximately 30 seconds.

  5. 5

    Check the "Cable" signal light on the front of the cable modem. If it is solid, test the Internet connection from a locally connected computer. If the light is blinking or absent, call your cable ISP for further assistance, as the problem is on your ISP's end.

Tips and warnings

  • Sometimes a simple flickering of the electrical power on site is enough to disconnect the cable Internet signal. Power-cycling both the cable modem and router usually restores the Internet connection.

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