- When experiencing problems with a cable modem Internet connection, the first--and, arguably, the simplest--thing to check is the status of the modem itself. Although different cable modems have different lights, displays and indicators, most modems have at least three standard commonalities. First, verify that the modem has power by looking for the "Power" light. If this light is out, or if the modem has no lights at all, the modem may be plugged into a faulty outlet or the power supply may have died (try a different power supply and electrical outlet for further testing). Next, the light labeled "Cable" should be on solid; this light indicates that the modem is receiving a signal from the cable company and is connected to the Internet. If this light is out, or if it's flashing, first verify that the coaxial cable is securely connected to both the modem and the wall, then inform the cable carrier. Next, the light labeled either "PC," "Computer" or "LAN" should be on (on some cable modems, this light may be flashing at an irregular rate; on other models, the light is solid and accompanied by a "Data" light that flashes to indicate the transfer of data packets). If this light is not functioning properly, there may be an issue with the connected router or computer that requires further troubleshooting. Finally, power cycle the modem by removing the power cord, waiting at least 30 seconds, and plugging the power cord back in. Cable modems sometimes "hang" and require a restart to restore proper functionality.
- If the indicator lights on the modem appear to be in order, the issue may be found in an attached network or in the computer itself. First, verify that all Ethernet cables are properly connected between the cable modem, router and any attached computers by pressing firmly on the plastic modular plugs connecting these devices. For wireless connections, try turning off the wireless connectivity, waiting 30 seconds, and reconnecting to the wireless access point. Next, connect a working computer directly to the cable modem, bypassing any routers or other network hardware. Renew the Internet protocol (IP) address of the computer by opening a command prompt and typing "ipconfig /renew" (on a Macintosh, open the "System Preferences" application, click on "Network," select the applicable network adapter, then click "Renew DHCP Lease"). If the computer connects to the Internet and is able to surf pages on the World Wide Web, there's a problem in the local area network that should be referred to a networking professional.
- If following the steps in Sections 1 and 2 don't restore Internet connectivity, there may be an Internet service outage. Contact the cable company or cable Internet provider and report trouble with the cable modem. If an outage is known, the representative will likely relay information such as the outage type (low signals, complete outages, fiber cuts or any number of other possible issues) and an estimated time of restoral (ETR). If the cable company is not yet aware of the outage, or if the outage is localized to only a few customers, the Internet provider may require some time to investigate the issue and may dispatch a technician for further troubleshooting.
