C4000XG modem user guide

Learn about using your C4000XG modem, including features and troubleshooting.

C4000 modem front and back views

Features of the C4000XG

  • 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 status light ring 
  • Dynamic QoS: Prioritizes data through the router for smoother streaming
  • Standards-based WiFi WPA3 security

Speed specifications

This gateway is tested and certified to run up to 940 Mbps on the Quantum Fiber network. 


Note: Speeds reflect the maximum download speed the technology can deliver Quantum Fiber service. In-home speeds may differ based on router setup, devices and other factors. 

Diagram of the C4000XG

C4000XG diagram with front light and rear ports


Top troubleshooting tips

  • Connection issues? Restarting your modem is a good first step to fix many common problems.
  • Tried restarting and still having trouble? Learn more about resetting the modem to its default settings.
  • Need more help? Our troubleshooting team is standing by. Contact us through your Quantum Fiber app, or by signing in to your account.

C4000 status light table

You can check this table for a summary of the light colors and what each one means. Or read on for a more detailed description of your modem lights and how to troubleshoot.

Light ring color Description
Blinking blue; solid blue Booting up; syncing with the network
Solid green Connected
Solid red Network failure; call or chat for help
Flickering green (fast) Sending or receiving data
Blinking green WPS trying to connect to a device
Blinking red WPS connection failed
Blinking amber-green or amber-white Updating firmware
Blinking green-red Network issue; call or chat for help
Off Not connected to the network


Finally, if instructed to do so by a member of our support team, you can download and install the latest modem firmware.