What Do the Lights on a Motorola Cable Modem Mean?

By Fred Decker

The lights on your AT&T modem can help you troubleshoot Internet connectivity issues.
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Motorola's series of SURFboard cable modems is widely used by Internet service providers. Like other modems, they use a series of lights to provide users with information about their status. Any computer user who's familiar with those lights and their meanings can tell at a glance whether the modem is working as it should.

Physical Arrangement

There are two main series of SURFboard modems, the SB5100 series and SB6100 series. Both are arranged vertically, standing upright on their narrow end rather than lying flat. The SB5100 series is generally slimmer and more contoured, with LED lights and text labels. The SB6100 series has lights in the same positions, but uses LEDs behind colored icons. This makes it easier for non-technical users to grasp what each light does, from across the room. From top to bottom, the lights represent Power, Receive, Send, Online, and Link or PC/Activity. The SB6100 series can have a sixth light, for its optional power-saving setting.

Basic Button Information

The Power button simply indicates that the modem is connected to an outlet and turned on. The Send and Receive lights indicate that your modem is communicating with your service provider's network. When they're flashing, it means your modem is attempting to establish a connection. When the lights stop flashing and remain on, it means you have a reliable connection. The Online light indicates that you have Internet service. When you turn on your modem, the lights will blink until your Internet connection is ready to use.The final light, reading either Link or PC/Activity, indicates that you have a computer, router or other device plugged physically into the modem.

Flashing Lights

In ordinary usage, only the PC/Activity light will flash. This is normal, and it simply means that the modem is transferring data between the Internet and your computer or router. If the Send, Receive or Online light begins to flash, this can indicate a problem with your connection. Sometimes, this is because your Internet provider is experiencing network difficulties. If you have friends nearby who use the same provider, check to see if they're experiencing problems. Otherwise, call your ISP's technical support. They can typically run diagnostics to determine whether the problem is with their network, or with your modem.

SB6100 Series

The SB6100 series modems support a newer version of the data over cable service standards, or DOCSIS. If your modem and ISP both support this newer DOCSIS 3.0 standard, you'll be able to send and receive at much higher speeds. If your SB6100 SURFboard shows green Send and Receive lights, that means you have a standard connection. However, if the lights are blue, that means you have a high-speed connection using bonded channels, each of which allows four times the bandwidth of a conventional channel. A blue Link light indicates that your computer is connected to the modem through a high-speed Gigabit Ethernet connection.