Using your C4000 modem

Learn about using your C4000 series modem/router, including features and speed specifications, popular modem settings, and troubleshooting. You can also watch a video about controling WiFi on your C4000.

Recommended CenturyLink modem

C4000 modem front and back

C4000 features

  • WiFi 6 technology with dual-band 2.4 GHz and 5 GHz 802.11ax
  • Smart Connect single wireless network (SSID): Auto-selects the fastest band for each device
  • Single LED status light 
  • Dynamic QoS: Prioritizes data through the router for smoother streaming
  • Standards-based WiFi WPA3 security

Speed specifications

This router comes in multiple versions with different specifications. The one you have depends on your internet connection type. Click to open the specific models below for speeds and downloadable info sheets.

The C4000BG and C4000BZ are tested and certified to run at these speeds* on the CenturyLink® High-Speed Internet network:

Technology Type Tested speed
ADSL2+ pair bond up to 40 Mbps
VDSL pair bond up to 140 Mbps

*Customer speed experiences will vary, particularly when accessing the internet wirelessly from different devices. Maximum download/upload speeds given are via a wired connection. Internet speeds are not guaranteed due to conditions outside of network control, including customer location, devices, equipment, and access over a wired or wireless connection; see centurylink.com/internetpolicy for more information.

The C4000LG and C4000LZ are tested and certified to run at these speeds* on the CenturyLink® High-Speed Internet network:

Technology Type Tested speed
ADSL up to 7 Mbps
ADSL2+ up to 20 Mbps
VDSL up to 100 Mbps

*Customer speed experiences will vary, particularly when accessing the internet wirelessly from different devices. Maximum download/upload speeds given are via a wired connection. Internet speeds are not guaranteed due to conditions outside of network control, including customer location, devices, equipment, and access over a wired or wireless connection; see centurylink.com/internetpolicy for more information.

The C4000XG is tested and certified to run at these speeds* on the CenturyLink® Fiber Internet network.

Technology Type Tested speed
Fiber up to 940 Mbps

*Customer speed experiences will vary, particularly when accessing the internet wirelessly from different devices. Maximum download/upload speeds given are via a wired connection. Internet speeds are not guaranteed due to conditions outside of network control, including customer location, devices, equipment, and access over a wired or wireless connection; see centurylink.com/internetpolicy for more information.

Diagram of the C4000XG modem

Diagram of the C4000XG modem

Top modem settings and tasks

Learn how to manage your internet and WiFi network using your modem. Below are some of our most popular topics. You can also visit the modem settings guide for a complete overview of settings and options.

Modem troubleshooting tips

  • Did you know?  If your internet connection is spotty or slow, the best place to start is to reboot your modem.

  • Still not running right? Check to see if your modem firmware is up to date.

Tip: If the firmware link doesn't work, try another browser (Chrome is known to have issues with this kind of link). Or, right-click the link, select "copy link address", then paste the link into a new browser tab.

Video: How to control your C4000 wireless settings

Need more WiFi? If you need to boost or extend your signal, consider ordering a WiFi extender from our Accessories shop, in the WiFi Performance area.

Starting new service? Please note that a phone jack is required to set up CenturyLink internet service in your home. If you don't have a jack, chat with us to have one installed.

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