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Linksys Support

Cable Modem with USB and Ethernet Connections (CM100)

• Modem for high-speed cable Internet connection
• Compatible with all DOCSIS Internet service providers
• “Always on” connectivity without monthly equipment rental charges 

View User Guide

Support Sections

Guide Me provides step-by-step solutions and troubleshooting tips. FAQs are frequently asked product questions. Select Downloads for user guides and firmware updates.

  • Overview
  • Guide Me
  • FAQs
  • Forums

    • Forums


    • Linksys Hardware Vs the ISP

      I'm having lots of Problems with my cable internet service charter tech that came over saw my stack of Linksys gear...

    • Linksys CM100

      I recently got a new Linksys CM100 cable modem. Is it advisable to have the cable modem standing or does it need to lie...

    • CM100 Status Page

      Downstream SNR shows the strength of the signal to your cable modem as compared to the noise on the line...

    • CM100 not finding signal

      Hi,I had a surfboard 4200 (motorola) and it worked fine for quite a few years but the speed would drop down for some reason...

    • Linksys CM100 firmware upgrade?

      Is there a firmware upgrade for the Linksys CM100? My CM100's web interface keeps crashing after a week of use.

    • BEFCMU10 versus CM100

      Hello everyone! Which cable modem is better; the Linksys BEFCMU10 Cable Modem or the Linksys CM100 Cable Modem? Than...

    • cm-100 no longer compatible with comcast

      I think I have read somewhere that CM100 is a docsis 2.0 modem only??? Or maybe I am wrong. Wizzard wrote:CM100 supports...

    • Port forwarding questions

      Finally figured out that it is an issue with the ports being blocked from my workplace, which is where I was trying to connect...

    • Block specific external ip address

      Not possible.1. Unless you forward a port the server can't be accessed anyway.2. If you forward a port to the server set...

    • Auto DHCP and Static IP together

      Definitely! That's the usual practice, if you have devices that needs port forwarding you set static IP address on it. Just...

    • File sharing with AVG 8.5 FW doesn't work

      I had a similar problem, and it turned out to be because I didn't create a new profile in the Firewall in AVG 8.5 Internet...

    • VPN connection Problem

      The port forwarding is under the Applications Gaming then Port Range Forward. The application filed can be anything you...

  • Downloads

    • Downloads

    Please ensure you select the correct hardware version as not all downloads are compatible with your device.

    Free Software notice for certain products, click here.

    Where's my model number?

    License Agreement
    Close

    How to find your model or serial number

    To find model or serial numbers, choose your device below.

    VALET HOTSPOTS

    •  

      Step 1:
      Flip the device over.

      Step 2:
      You should find the model number on the sticker underneath the device. Please see the example.

      Step 3:
      Take note of the exact model number and version of your product. The serial number is located right underneath the model number. In this example, the model number of the device is M20.

      NOTE: The images may vary depending on the exact model number of your Linksys Product. If there is no version number beside the model number it means that is version 1.

    WIRELESS ROUTERS AND ACCESS POINTS

    • E-Series

      Step 1:
      Look at the top of the device.

      Step 2:
      The model number should be found under the CISCO logo.

      NOTE: The images may vary depending on the exact model number of your Linksys product. The serial number is located underneath the device. If there is no version number beside the model number, it means that it is a version 1.

    • Blue and Black

      Step 1:
      Flip the device over.

      Step 2:
      You should find the model number on the sticker underneath the device. Please see the example.

      Step 3:
      Take note of the exact model number and version of your Linksys device. The serial number is located right underneath the model number. In this example, the model number of the device is WRT54G ver 6.

      NOTE: The images may vary depending on the exact model number of your Linksys Product. If there is no version number beside the model number it means that is version 1.

    • Silver

      Step 1:
      Look at the side panel of the router when it is standing vertically.

      Step 2:
      You should find the model number on the sticker. Please see the example.

      NOTE: The images may vary depending on the exact model number of your Linksys Product. If there is no version number beside the model number it means that is version 1.

      Step 3:
      Take note of the exact model number and version of your Linksys device. The serial number is located right underneath the model number. In this example, the model number is WRT54GX4.

    • Wireless Routers with Voice Ports

      Step 1:
      Look at the side panel of the router when it is standing vertically.

      Step 2:
      You should find the model number on the sticker. Please see the example.

      NOTE: The images may vary depending on the exact model number of your Linksys Product. If there is no version number beside the model number it means that is version 1.

      Step 3:
      Take note of the exact model number and version of your Linksys device. The serial number is located right underneath the model number. In this example, the model number is WRTP54G V.2.

    • Wireless VPN Routers

      Step 1:
      Look at the side panel of the router when it is standing vertically.

      Step 2:
      You should find the model number on the sticker. Please see the example.

      NOTE: The images may vary depending on the exact model number of your Linksys Product. If there is no version number beside the model number it means that is version 1.

      Step 3:
      Take note of the exact model number and version of your Linksys device. The serial number is located right underneath the model number. In this example, the model number is WRV54G.

    WIRED ROUTERS

    • Blue and Black

      Step 1:
      Flip the device over.

      Step 2:
      You should find the model number on the sticker underneath the device. Please see the example.

      Step 3:
      Take note of the exact model number and version of your Linksys device. The serial number is located right underneath the model number. In this example, the model number of the device is BEFSR41 ver.4.1.

      NOTE: The images may vary depending on the exact model number of your Linksys Product. If there is no version number beside the model number it means that is version 1.

    WIRELESS ADAPTERS

    • PC Card or Card Bus

      Step 1:
      If your adapter is already connected to the computer, shut down your computer and remove the adapter.

      Step 2:
      You should find the model number on the device itself. Please see the example.

      Step 3:
      Take note of the exact model number and version of your Linksys device. The serial number is located right underneath the model number. In this example, the model number is WPC54G ver.7

      NOTE: The images may vary depending on the exact model number of your Linksys Product. If there is no version number beside the model number it means that is version 1.

    • PCI Adapter

      Step 1:
      If your adapter is already connected to the computer, shut down your computer and remove the adapter.

      Step 2:
      You should find the model number on the device itself. Please see the example.

      NOTE: The images may vary depending on the exact model number of your Linksys Product. If there is no version number beside the model number it means that is version 1.

      Step 3:
      Take note of the exact model number and version of your Linksys device. The serial number is located right underneath the model number. In this example, the model number is WMP54G ver.4.1.

    • USB Wireless Adapter

      Step 1:
      Look for the sticker around the device.

      Step 2:
      You should find the model number on the sticker. Please see the example.

      NOTE: The images may vary depending on the exact model number of your Linksys Product. If there is no version number beside the model number it means that is version 1.

      Step 3:
      Take note of the exact model number and version of your Linksys device. The serial number is located right underneath the model number. In this example, the model number is WUSB54G ver.4.

    WIRED ADAPTERS

    • PCI Adapters

      Step 1:
      If your adapter is already connected to the computer, shut down your computer and remove the adapter.

      Step 2:
      You should find the model number on the device itself. Please take note of the exact model number and version. Please see the example.

      Step 3:
      Take note of the exact model number and version of your Linksys device. The serial number is located right underneath the model number.

      NOTE: The images may vary depending on the exact model number of your Linksys Product. If there is no version number beside the model number it means that is version 1.

    SWITCHES

    • SE Switches

      Step 1:
      Look at the top of the device.

      Step 2:
      The model number should be found under the CISCO logo.

      Step 3:
      Take note of the exact model number and version of your product. The serial number is located underneath the device. In this example, the model number of the device is SE1500.

      NOTE: The images may vary depending on the exact model number of your Linksys product. If there is no version number beside the model number, it means that it is a version 1.

    MEDIA HUB

    •  

      Step 1:
      Flip the device over.

      Step 2:
      You should find the model number on the sticker underneath the device. Please see the example.

      Step 3:
      Take note of the exact model number and version of your Linksys device. The serial number is located right underneath the model number. In this example, the model number of the device is NMH410.

      NOTE: The images may vary depending on the exact model number of your Linksys Product. If there is no version number beside the model number it means that is version 1.

    WIRELESS HOME AUDIO

    •  

      Step 1:
      Flip the device over.

      Step 2:
      You should find the model number on the sticker underneath the device. Please see the example.

      Step 3:
      Take note of the exact model number and version of your Linksys device. The serial number is located right underneath the model number. In this example, the model number of the device is DMC250.

      NOTE: The images may vary depending on the exact model number of your Linksys Product. If there is no version number beside the model number it means that is version 1.

  • Videos
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Forums


  • Linksys Hardware Vs the ISP

    I'm having lots of Problems with my cable internet service charter tech that came over saw my stack...

  • Linksys CM100

    I recently got a new Linksys CM100 cable modem. Is it advisable to have the cable modem standing or does...

  • CM100 Status Page

    Downstream SNR shows the strength of the signal to your cable modem as compared to the...

  • CM100 not finding signal

    Hi,I had a surfboard 4200 (motorola) and it worked fine for quite a few years but the speed would drop...

See All Forum Topics

Guide Me

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