If you use a Motorola SURFboard SB5100 as your cable modem (or any cable modem, for that matter), there will be times when you can't connect to the Internet. Luckily it's not hard to follow a simple checklist for troubleshooting basic problems with your modem.
Make sure the power cord is properly plugged into both the modem and the outlet. If it is, make sure the outlet is working. Plug another device into the outlet to make sure it works. Also, make sure the modem is not set on standby. Try pressing the standby button.
Trouble Connecting to the Internet
Make sure all of four of the green lights on the front of the modem are illuminated. Check the coaxial cable connection going to the modem. Ensure that it is securely connected. Also, check out your cable television. If you can't get a cable signal for your television you likely won't get an Internet connection either.
Power Cycle Your SURFboard
Shut off your computer and unplug your router if you have one. Next, unplug your SURFboard. Wait five minutes and plug it back in. This resets the modem and requests a new IP address from your Internet service provider (ISP). Once the modem has completely booted back up, and all four lights on the front panel are green, plug your router back in. After your router is up and running, turn on your PC. If that does not work, move on to the next step.
Contact Motorola and Your ISP
First, contact your ISP to make sure they aren't having problems on their end. If they determine it is a problem with your modem, contact Motorola at (877) 466-8646. You can also visit Motorola's customer service site (see Resources for link).