Setting up your new Technicolor C2100T is only as easy as the instructions you follow. On this page you can find instructions developed over many years of working with our clients and helping them set up their new equipment. We’re happy to share our tips and secrets so you can spend as little time on hold as possible!

How to Reset Technicolor C2100T

Resetting your Technicolor C2100T is one of the easiest troubleshooting steps you can try first when something isn’t working right. This quick process will restore your modem router combo to factory default settings so that you can narrow down what could be causing the problem. It can also be helpful for when you’ve forgotten the WiFi password or are having connection problems.

  1. Plug in your C2100T and allow it to power on fully. Once the WiFi lights are on, you’ll be ready to begin your reset.
  2. After it’s booted up fully, locate the reset button hole on the back of your modem. It’ll be among the other ports on the back.
  3. Press and hold down the reset button with a paperclip for 30 seconds.
  4. Allow 2-3 minutes for your modem to power cycle and reset itself. When the WiFi lights are back on, you’re good to go to use your newly reset device!

How to Activate C2100T with CenturyLink

Similar to activating your new phone when you upgrade every few years, modems need to be activated with your provider before you can use them to access the internet. Your provider needs some of the unique identifiers on the bottom or back sticker of your modem to get it added to their system and link it to your account. This also usually involves your provider loading firmware onto your modem that allows it to work correctly with their services.

Installing and activating with CenturyLink is usually a pretty quick process compared with some other providers. Activating with CenturyLink starts with calling your provider’s customer service activation line or using their online activation portal (if available in your area). During this process your provider will ask for your modem’s serial number, MAC address as well as identifying information about your account such as your residential address and other information that is unique to your account.

Online Self-Installation with CenturyLink

CenturyLink now has a completely digital way to activate your modem. This way, you no longer are required to call CenturyLink customer service or have a technician come out to your house to install your equipment. You can do it from the comfort of your armchair without having to talk to anyone. To get started, head over to CenturyLink’s informational page on self-installing your modem. They’ll quickly walk you through activation and setting up your WiFi in addition to other network settings that may boost your service.

Calling CenturyLink Customer Service

Alternatively, for some it may be easier to just call their customer service. Most of the time this will take a bit longer than going the online self-activation route, but it’s definitely still faster than waiting for a technician to come to your home. CenturyLink’s customer service phone number is 866-642-0444.

How to Change the WiFi Password on Technicolor C2100T DSL Modem

Changing the WiFi password on the Technicolor C2100T DSL modem is a relatively simple process. Follow the steps below and youll have a secure, new WiFi password in no time.

1. Connect to the modem. Before you can start changing your WiFi password, you need to connect to the modem. This can be done either through a wired connection or through the WiFi connection itself.

2. Open your web browser. Once youre connected to the modem, open up any web browser, such as Chrome, Firefox, or Safari. We recommend avoiding Microsoft Edge for the best experience. 

3. Enter the modems IP address. The modems IP address can be found in the modems manual or on the back of the modem. Type the IP address into the address bar of your web browser.

4. Enter your login details. You will be prompted to enter your login details. This is usually the username and password printed on your modem’s sticker. If you’ve changed this at any point and dont know your login information, you may have to reset your modem.

5. Select theWireless tab. Once youve logged in, you will be taken to the main page of the modems settings. Find theWireless tab and select it.

6. SelectSecurity Settings. Once youre in the Wireless tab, you will be able to view the current security settings for your WiFi connection. SelectSecurity Settings to access the settings for your WiFi password.

7. Change the WiFi password. In the Security Settings, you will be able to enter a new WiFi password. Type in your desired password and selectSave.

8. Disconnect and reconnect. Once youve changed the WiFi password, you will need to disconnect and reconnect your devices to the modem. Enter the new WiFi password when prompted, and you should now be connected to the modem with the new password.

And thats all there is to it! Changing the WiFi password on your Technicolor C2100T DSL modem is a quick and painless process. Make sure to choose a secure password and change it regularly to keep your network safe.

Resolving C2100T WiFi Issues

WiFi issues can be caused by a variety of things – from a new version of firmware to adding a bridged WiFi router to your setup. It’s important to figure out WHY the wireless in your modem isn’t working properly so you can work towards a fix for it. Before beginning this sequence of steps, we recommend disconnecting any range extenders, wireless routers, switches and other networking accessories from your setup as these can complicate things and we want to narrow down where the issue is actually coming from. You can troubleshoot those other devices later, but before that we want to ensure that the internet is coming through from the source, as it should be.

Check that you are able to access the internet with a wired connection.

When modems are activated properly, they should have internet coming through them right away. If your modem was not activated properly, you not only will have issues accessing internet from your WiFi, but also with a wired connection. Occasionally we see devices that were just not activated fully/correctly. If this is the issue with your setup, this is a super easy fix that you can do yourself by simply calling your provider to have them finish activating.

If you can access the internet via Ethernet cable but no WiFi network(s) show up:
    • The modem’s internal settings may be mis-configured so that the built-in wireless has been disabled by accident. Sometimes the firmware that your service provider loads on your modem will disable this. We recommend first trying a factory reset since at factory default settings, the WiFi is on and broadcasting with the factory default credentials listed on the modem’s sticker.
    • If a factory reset does not work for some reason, you’ll need to log into the settings of your modem manually to turn the WiFi back on.
      1. Connect your modem to your computer via Ethernet cable (yes, Ethernet connection is required since you can’t connect to wireless).
      2. Open an internet browser window (preferably Google Chrome, Safari or Firefox, NOT Microsoft Edge/Internet Explorer)
      3. Into the URL bar at the top of your window type in: (or whatever your modem says is the “IP address”)
      4. It should bring you to a login page. Use the username and password on your modem’s sticker to log in.
      5. Head over to the wireless settings page, and ensure that your wireless is set to “enabled”.
      6. Make sure to hit SAVE if you made any changes so you don’t have to start over. You should now be able to connect to your modem’s wireless.
If you cannot access internet via Ethernet cable:
    • The modem is probably not activated fully. To correct this, you’ll need to call your provider to have them activate it. If they claim that it has been activated but you’re still not able to access Wired or Wireless internet, have them read back the serial number they have on file for you to verify they’ve got the right equipment logged in your account.
    • If the equipment is correct, and they’ve tried to help troubleshoot with you, it’s possible that your modem is defective. You’ll need to contact the vendor you purchased your C2100T from to do a return or a replacement. Devices purchased from are covered by our warranty which provides expedited replacements. Contact us to get one requested!

Tl;dr: If you don’t have internet at all, call your provider.

Understanding C2100T Indicator Lights

Your C2100T’s LED lights are the gateway to understanding what’s going on internally. If you ever experience connectivity issues or if you’re just curious, knowing how to interpret these lights can be very useful.

1. Power Light

  • Solid Green: Power is ON.
  • Blinking Green: Device is starting up.
  • Red: There is a device malfunction. Try resetting or contact support.
  • Off: Power is OFF.

2. DSL Light

  • Solid Green: A successful DSL connection is established.
  • Blinking Green: Device is trying to establish a DSL connection.
  • Red: No DSL connection found. Check cables or contact your service provider.
  • Off: No DSL activity.

3. Internet Light

  • Solid Green: Internet connection is successful.
  • Blinking Green: Device is establishing an Internet connection.
  • Red: No Internet connection. Check your activation status or contact your service provider.
  • Off: Internet is not set up.

4. WiFi Lights (2.4G and 5G)

  • Solid Green: WiFi is ON and active.
  • Blinking Green: Data is being transferred over WiFi.
  • Off: WiFi is OFF or not broadcasting.

5. Ethernet Lights (1-4)

  • Solid Green: A device is connected via the respective Ethernet port.
  • Blinking Green: Data is being transferred over the respective Ethernet port.
  • Off: No device connected to the respective Ethernet port.

6. WPS Light

  • Solid Green: WPS is enabled and ready for connection.
  • Blinking Green: WPS is active and a connection is in progress.
  • Off: WPS is not active.

7. Phone Light (If applicable)

  • Solid Green: Phone line is active and ready.
  • Blinking Green: An incoming or outgoing call is in progress.
  • Off: No phone line detected.

Troubleshooting with the Lights

If your lights indicate an issue, here are a few quick solutions to try:

  • No Power: Ensure the device is plugged into a working outlet and the power cord is securely connected.
  • No DSL Connection: Check the DSL line for any damages or disconnections. If it’s intact, contact your service provider.
  • No Internet: Reset the modem. If the issue persists, ensure the device is activated with CenturyLink.
  • WiFi Off: Check the modem’s settings to ensure the WiFi is enabled. Resetting the modem might help too.

Always remember, the LED indicators are the first step in understanding any potential issues. If you ever face an inconsistency between the LED indications and your actual connection status, a reset or a call to the service provider might be necessary.

Common Technical Issues with the Technicolor C2100T and Troubleshooting Steps

While the Technicolor C2100T is a reliable modem-router combo, like any piece of technology, it’s not without its quirks. Below are common technical issues users might encounter and steps to troubleshoot them.

1. Slow Internet Speed Potential Causes & Solutions:

  • Too many devices: If many devices are connected and using bandwidth-intensive tasks, it could slow down the internet for everyone. Disconnect unnecessary devices and check speed.
  • Distance from the router: The further a device is from the router, the weaker the signal. Try moving closer or consider investing in a Wi-Fi extender.
  • Firmware outdated: Ensure that your modem’s firmware is updated. Sometimes, service providers push updates that can improve performance.

2. Intermittent Connection Drops Potential Causes & Solutions:

  • Overheating: Ensure the modem is in a well-ventilated area. Overheating can cause connection drops.
  • Signal interference: Other electronic devices or neighboring Wi-Fi networks can interfere. Consider changing the Wi-Fi channel from the modem’s settings.
  • Faulty cables: Ensure that all cables connected to the modem are in good condition and securely connected.

3. Can’t Connect to Wi-Fi Potential Causes & Solutions:

  • Incorrect Password: Ensure you’re entering the correct Wi-Fi password.
  • Wi-Fi is disabled: Log into the modem settings and make sure the Wi-Fi is enabled.
  • Device limit reached: Some modems have a limit on how many devices can connect. Disconnect unused devices and try again.

4. Can’t Access Modem’s Web Interface Potential Causes & Solutions:

  • Wrong IP Address: The default is usually If changed, you’ll need to use the updated IP address.
  • Browser issue: Some browsers may have compatibility issues. Try a different browser.

5. USB Port Not Recognizing Connected Devices Potential Causes & Solutions:

  • Incompatible device: Not all devices might be compatible with the USB port on the modem. Check the modem’s manual for supported devices.
  • Faulty USB device: Try connecting the device to a computer to check if it’s working.

6. No Dial Tone on Phone Line (If applicable) Potential Causes & Solutions:

  • Faulty phone cables: Check if the phone cables are intact and properly connected.
  • Phone settings: Ensure the phone settings in the modem’s interface are correctly configured.

7. LED Lights Not Displaying Correctly Potential Causes & Solutions:

  • Temporary glitch: Sometimes, a simple reset can solve LED light issues.
  • Faulty hardware: If the lights still don’t display correctly after a reset, the hardware might be faulty. Consider replacing the unit.

General Troubleshooting Tips:

  • Restart the Modem: Many minor glitches can be resolved by simply unplugging the modem, waiting for a minute, and plugging it back in.
  • Factory Reset: If you’ve tried the above steps and still face issues, consider a factory reset. However, remember that this will erase all your custom settings.
  • Contact Support: If all else fails, reach out to CenturyLink or the modem’s support team. They might have insights into specific issues, especially if it’s a known problem with a certain batch or model.

By identifying the specific issue you’re facing and systematically working through potential causes and solutions, you can often resolve technical problems without needing to call in professional help.

Did we answer all your questions about the CenturyLink Technicolor C2100T DSL Modem? Let us know in the comments, or leave your own questions for our technicians to answer!

5 thoughts on “Technicolor C2100T Troubleshooting Guide: Solutions for Common Issues

  1. Eric Abbott says:

    What’s the USB port on the rear of the unit for? There’s no category for this status light in the information section of this web page.

    1. ModemGuides says:

      Hi Eric!

      Some devices like the C2100T for Centurylink come with a USB port on the back. A USB port on a router or modem-router allows you to connect a printer or external hard drive for sharing files and media on your home network. It’s a bonus feature that is not connected to your internet service so it typically won’t get a status light on the front of most devices.

      Hope that helps!

      – MG Support

  2. Gary S. says:

    I got a C2100T from Centurylink but the USB port on the back was disabled. When I talked to a tech they said it was done on purpose and would not tell me how to enable it. Is there a way to enable the USB port on the C2100T and if so how?


  3. Tom R says:

    I am wondering if this can be used in dual mode, ie 2.4 and 5 g? I have a device that needs the 2.4g but my others need 5g. Is this capable of duplex transmission?

    1. ModemGuides says:

      Hi Tom!

      The Technicolor C2100T DSL modem for CenturyLink is a dual-band device that can operate in both 2.4 GHz and 5 GHz frequency bands simultaneously. This means that it is capable of duplex transmission and can provide wireless coverage to devices that require either 2.4 GHz or 5 GHz frequencies. You can configure the modem’s wireless settings to enable both frequency bands and connect your devices to the appropriate network based on their wireless capabilities.

      Hope that helps! Please let us know if we can help with any additional questions!

      – ModemGuides Support

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