Check your modem cords

Troubleshooting an internet connection issue? One important step is to check that all your modem cables are plugged in correctly. 

What cords should you have?

  • Power cord (black)
  • Ethernet cables (yellow and white)
  • DSL cable (green) - not used with fiber modems like the C4000XG

How to check your modem cord connections

Select your type of modem below to see instructions.

Now it's time to get your modem hooked up.

  1. Plug the black power cord into a wall outlet and into the power port on the back of the modem. 
  1. For the C4000BG or LG/LZ, plug one end of the green cord into the green DSL port on back of the modem, and the other end into a working phone jack. Note that the C4000XG does not have a DSL port. 
C4000 DSL port and power

DSL and power ports on the back of the C4000BG and LG/LZ models

  1. Finally, plug one end of the yellow Ethernet cord into one of the Ethernet ports on the modem, and the other end into your computer's Ethernet port. 

No Ethernet port? If you are using a tablet or newer laptop, you may not have an Ethernet port on your device. That's okay. If your device doesn't have Ethernet, you can instead connect to WiFi using the login information on the bottom of the modem.

C4000 bottom label

If you see a white cord in your modem kit, it's a second Ethernet cable to be used in case you have additional devices that you would like to plug into the modem.

check modem cords plugged in

Now it's time to get your modem hooked up. 

  1. Plug the black power cord into a wall outlet and into the power port on the back of the modem. 

  2. Plug one end of the green cord into the green DSL port on back of the modem, and the other end into a working phone jack. 

  3. Finally, plug one end of the yellow Ethernet cord into one of the Ethernet ports on the modem, and the other end into your computer's Ethernet port.
Back of modem showing DSL ports, Ethernet ports, power port

Note: Your modem may look different from the one in the image, but the ports on any tower or box-style modem will be similar.


Do you have both internet and home phone service from CenturyLink?

If you have both landline phone service (not VOIP) and high-speed internet, you will need to install DSL filters on all of your phone cords. These are essential to make sure you get the best phone and internet connection. 

Filters are not needed if you use the C4000XG

Phone plugging into filter (diagram)

Plug the phone cord into a filter and then into the wall jack.

Note: If you have cordless phones, you only need to install a filter on the phone base that plugs in to the wall jack; no filters are needed on the cordless units that only plug into an electrical outlet.


Modem plugging in with no filter (diagram)

The DSL cord from the modem to the jack should not have a filter.


Phone and modem plugging into DSL splitter (diagram)

Use a DSL splitter to plug the modem and a telephone into one wall jack.

How to check the modem status lights

The modem status lights can tell you if your connection is good or if there's an error. Learn more about how to read your modem status lights by selecting your modem type.

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