NETGEAR CM400 User manual

350 East Plumeria Drive
San Jose, CA 95134
USA
September 2017
202-11412-03
High Speed Cable Modem
Model CM400
User Manual

2
CM400 High Speed Cable Modem
Support
Thank you for purchasing this NETGEAR product. You can visit www.netgear.com/support to register your product, get help,
access the latest downloads and user manuals, and join our community. We recommend that you use only official NETGEAR
support resources.
Conformity
For the current EU Declaration of Conformity, visit http://kb.netgear.com/app/answers/detail/a_id/11621.
Compliance
For regulatory compliance information, visit http://www.netgear.com/about/regulatory.
See the regulatory compliance document before connecting the power supply.
Trademarks
© NETGEAR, Inc., NETGEAR and the NETGEAR Logo are trademarks of NETGEAR, Inc. Any non-NETGEAR trademarks are
used for reference purposes only.EAR logo are trademarks of NETGEAR, Inc. Any non-NETGEAR trademarks are used for
reference purposes only.

3
Contents
Chapter 1 Hardware and Internet Setup
Unpack Your Cable Modem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Front Panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Back Panel. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Product Label . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Attach the Feet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Cable Your Cable Modem. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Install and Activate Your Cable Modem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Activate Your Internet Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Activate Your Internet Service With Comcast XFINITY. . . . . . . . . . . . . . . . . . 10
Perform a Speed Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Connect Your Cable Modem to a Router After Installation and Activation . . . 12
Chapter 2 Manage and Monitor
Log In to the Cable Modem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Specify the Cable Connection Starting Frequency . . . . . . . . . . . . . . . . . . . . . . . 14
View Cable Modem Initialization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
View Cable Modem Status. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
View and CLear Event Logs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Change the admin Password . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Reboot the Cable Modem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Reset the Cable Modem to Factory Default Settings . . . . . . . . . . . . . . . . . . . . . 18
Use the Reset Button on the Back Panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Use the Factory Reset Software Button . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Chapter 3 Troubleshooting
Use LEDs to Troubleshoot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Cannot Log In to the Cable Modem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Troubleshoot the Cable Internet Connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Appendix A Technical Specifications

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1
1. Hardware and Internet Setup
The NETGEAR CM400 High Speed Cable Modem provides a connection to high-speed cable
Internet with speeds up to 340 Mbps.1The cable modem is certified by all major cable Internet
providers. A Gigabit Ethernet port provides fast access and downloads. The cable modem
supports IPv4 and IPv6 address assignment by cable Internet providers.
This chapter covers the following topics:
•Unpack Your Cable Modem
•Front Panel
•Back Panel
•Product Label
•Attach the Feet
•Cable Your Cable Modem
•Install and Activate Your Cable Modem
•Connect Your Cable Modem to a Router After Installation and Activation
Note: For more information about the topics covered in this manual, visit the
support website at http://support.netgear.com.
1. Maximum rate is derived from DOCSIS 3.0 specifications and actual throughput varies depending on your Internet subscription with your provider.

Hardware and Internet Setup
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CM400 High Speed Cable Modem
Unpack Your Cable Modem
Your package contains the following items.
Ethernet cable Power adapter
Cable modem Attachable feet
Figure 1. Package contents
Front Panel
The cable modem provides status LEDs on the front.
Power LED
Downstream LED
Upstream LED
Internet LED
Ethernet LED
Figure 2. Cable modem front view

Hardware and Internet Setup
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CM400 High Speed Cable Modem
You can use the LEDs to verify status and connections. The following table lists and
describes each LED on the front panel of the cable modem.
Table 1. LED descriptions
LED Description
Power • Green. Power is supplied to the cable modem.
• Off. No power is supplied to the cable modem.
Downstream • Solid amber. One downstream channel is locked.
• Solid green. Two or more downstream channels are locked.
• Blinking green. The cable modem is scanning for a downstream channel.
• Off. No downstream channel is locked.
Upstream • Solid amber. One upstream channel is locked.
• Solid green. Two or more upstream channels are locked.
• Blinking green. The cable modem is scanning for an upstream channel.
• Off. No upstream channel is locked.
Internet • Solid green. The cable modem is online.
• Blinking green. The cable modem is synchronizing with the cable provider’s cable
modem termination system (CMTS).
• Off. The cable modem is offline.
Ethernet • Green. A powered-on device is connected to the Ethernet port at 1000 Mbps.
• Amber. A powered-on device is connected to the Ethernet port at 10/100 Mbps.
• Blinking green or amber.The Ethernet port is processing traffic.
• Off. No device is connected to the Ethernet port.
Back Panel
The back panel provides the connections and button shown the following figure.
Power adapter input
LAN Gigabit Ethernet port
Coaxial cable connector
Reset button
Figure 3. Cable modem back panel

Hardware and Internet Setup
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CM400 High Speed Cable Modem
Product Label
The product label on the bottom of the cable modem displays the serial number and MAC
address of the cable modem and login information, including the default IP address,
default user name, and default password.
Figure 4. Product label
Attach the Feet
The cable modem functions well in either a horizontal or vertical position.
If you prefer to place the cable modem in the upright (vertical) position, attach the feet that
come with the cable modem.
To attach the feet:
1. Hold the cable modem in the upright position with the left side of the cable modem pointing
down.
2. Snap the feet onto the cable modem.
Figure 5. Attaching the feet

Hardware and Internet Setup
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CM400 High Speed Cable Modem
Cable Your Cable Modem
The cable modem provides a connection between your cable Internet provider’s network and
your computer, router, or WiFi router.
Computer,
router, or
WiFi router
Cable modem
Coaxial cable to cable outlet
Ethernet
cable
Figure 6. Cabling the cable modem
To cable your cable modem:
1. Connect a coaxial cable.
Use the coaxial cable that your cable company provided to connect the cable port on the
cable modem to a cable wall outlet or a line splitter. Make sure that the cable is tightly
connected.
Note: If Comcast XFINITY is your cable Internet provider, Comcast XFINITY
recommends connecting your cable modem directly to a cable wall outlet.
2. Turn off the computer to which you intend to connect the cable modem.
3. Use the Ethernet cable provided in the package to connect the Gigabit Ethernet port on the
cable modem to an Ethernet port on the computer.
4. Turn on the computer.
5. Connect the power adapter provided in the package to the cable modem and plug the power
adapter into an electrical outlet.
When the startup procedure is completed, the Power LED lights green.
6. Wait for the cable modem to come online.

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CM400 High Speed Cable Modem
It takes at least 10 minutes for the cable modem to come online on the network. During
this time, the LED behavior is as follows:
•The Downstream LED lights amber when one downstream channel is locked.
•The Downstream LED lights green when more than one downstream channel is
locked.
•The Upstream LED lights amber when one upstream channel is locked.
•The Upstream LED lights green when more than one upstream channel is locked.
•After the cable modem registers with your cable Internet provider, the Internet LED
lights green.
Even though an Internet connection is established, Internet service is available only after you
set it up with your cable Internet provider.
For information about how to set up your Internet service, see Activate Your Internet Service
on page 9.
Install and Activate Your Cable Modem
The cable modem provides a connection between your cable Internet provider’s network and
your computer, router, or WiFi router.
Activate Your Internet Service
Before you activate your Internet service, collect the following information:
•Your cable Internet provider account information
•Cable modem model number, which is CM400
•Cable modem serial number
•Cable modem MAC address
Your cable modem’s serial number and MAC address are on the cable modem label.

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CM400 High Speed Cable Modem
To activate your Internet service:
1. Visit your cable Internet provider’s website and follow the onpage instructions to activate
your Internet service.
Cable Internet Provider Contact Information
Bright House Networks
(Spectrum)
http://support.brighthouse.com
1-855-222-0102
Cablevision
(Optimum)
http://www.cablevision.com
https://install.optimum.com/JointInstall/
Telephone number depends on your region.
Charter
(Spectrum)
https://install.charter.com
1-800-892-4357
Comcast XFINITY https://www.comcast.com/activate
http://www.xfinity.com/internetsetup
http://www.xfinity.com/internetsupport
1-855-OK-BEGIN (1-855-652-3446)
1-800-XFINITY (1-800-934-6489)
For more information, see Activate Your Internet Service With Comcast
XFINITY on page 10.
Cox https://activation.cox.net/selfactivation/start.cox
1-888-556-1193
Mediacom https://maestro.mediacomcc.com/walledgarden/page/login.jsp
1-844-2SIMPLE (1-844-274-6753)
Note: Your cable Internet provider’s contact information might change. You
can also find the contact information in your monthly Internet service
billing statement.
2. If you are unable to activate your Internet service using the instructions on your cable
Internet provider’s website, call your cable Internet provider for support.
Activate Your Internet Service With Comcast XFINITY
Activate your Internet service by using Comcast XFINITY’s self-activation process. If you are
unable to self-activate your cable modem, call Comcast XFINITY customer service. After you
complete the setup, perform a speed test.
Before you start the self-activation process, collect the following information:
•XFINITY account number
Note: When you attempt to contact Cablevision online, you are
directed to the Optimum web page. Optimum is a brand name of
Cablevision.

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CM400 High Speed Cable Modem
•The phone number associated with your XFINITY account
•XFINITY login information (your email address or user name and password)
•Cable modem model number, which is CM400
•Cable modem serial number
•Cable modem MAC address
Your cable modem’s serial number and MAC address are on the cable modem label.
To set up your Internet connection with Comcast XFINITY’s self-activation process:
1. Close all web browsers.
2. Launch a web browser.
You are redirected to the XFINITY self-activation page. If you are not redirected to the
XFINITY self-activation page, visit http://www.comcast.com/activate.
3. Provide your XFINITY credentials and complete the self-activation process.
This process might take up to 15 minutes, during which the cable modem reboots twice.
4. If you are unable to activate your cable modem using the XFINITY self-activation process,
call 1-855-OK-BEGIN (1-855-652-3446) or 1-800-XFINITY (1-800-934-6489).
Perform a Speed Test
To determine the accurate Internet speed, visit the speed test website of your cable Internet
provider and perform a speed test.
If your actual speed is lower than your subscribed speed, contact your cable Internet
provider.

Hardware and Internet Setup
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CM400 High Speed Cable Modem
Connect Your Cable Modem to a Router After Installation
and Activation
During the installation and activation, you must connect the cable modem directly to a
computer. After installation and activation, you can connect the cable modem to a router.
Router
Cable modem
Coaxial cable to
Ethernet cable
Power adapter
Computer
cable outlet
Figure 7. Connect the cable modem to a router
To connect your cable modem to a router after installation and activation:
1. Reboot the cable modem by unplugging the power cable from the cable modem and
plugging it back in.
Note: Do not disconnect the cable modem from the cable outlet.
When the startup procedure is completed, the Power LED lights green.
Wait for the Internet LED to stop blinking and light solid green.
2. Use an Ethernet cable to connect the Ethernet port on the cable modem to the WAN or
Internet port on the router.
3. Power on the router.
Wait until the router is ready.
4. Connect a computer to the router over a WiFi connection or with an Ethernet cable to a LAN
port on the router.

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2. Manage and Monitor
After you set up the cable modem, you do not need to log in to the cable modem for normal
operation. However, you can log in to the cable modem to change some very limited settings and
monitor the cable modem. In the unlikely situation that you experience problems with the cable
connection and cannot get an Internet connection, technical support might ask you to log in to
the router.
This chapter contains the following sections:
•Log In to the Cable Modem
•Specify the Cable Connection Starting Frequency
•View Cable Modem Initialization
•View Cable Modem Status
•View and CLear Event Logs
•Change the admin Password
•Reboot the Cable Modem
•Reset the Cable Modem to Factory Default Settings

Manage and Monitor
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CM400 High Speed Cable Modem
Log In to the Cable Modem
After you set up the cable modem, you do not need to log in to the cable modem for normal
operation.
To log in to the cable modem, you must use a web browser such as Microsoft Internet
Explorer 5.0 or later, Firefox Mozilla 2.0 or later, Safari 1.4 or later, or Google Chrome 11.0 or
later.
To log in to the cable modem:
1. Launch a web browser from a computer that is attached over an Ethernet cable to the
cable modem or from a computer that is connected to a WiFi router that is attached over an
Ethernet cable to the cable modem.
2. Type http://192.168.100.1.
A login page displays.
3. Enter the cable modem user name and password.
The user name is admin. The default password is password. The user name and
password are case-sensitive.
The BASIC Home page displays.
Specify the Cable Connection Starting Frequency
The starting frequency for the cable connection is automatically generated. For most Internet
connections, you do not need to specify this information. If you need to enter a starting
frequency, contact your Internet provider.
To change the starting frequency:
1. Launch a web browser from a computer that is attached over an Ethernet cable to the
cable modem or from a computer that is connected to a WiFi router that is attached over an
Ethernet cable to the cable modem.
2. Type http://192.168.100.1.
A login page displays.
3. Enter the cable modem user name and password.
The user name is admin. The default password is password. The user name and
password are case-sensitive.
The BASIC Home page displays.
4. Select Cable Connection.
The Cable Connection page displays.
5. In the Starting Frequency field, type a number.

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CM400 High Speed Cable Modem
6. Click the Apply button.
Your change takes effect.
View Cable Modem Initialization
You can track the initialization procedure of the cable modem and get details about the
downstream and upstream cable channel. The time is displayed after the cable modem is
initialized.
The cable modem automatically goes through the following steps in the provisioning process:
1. Scans and locks the downstream frequency and then ranges the upstream channels.
2. Obtains a WAN IP address for the cable modem.
3. Connects to the Internet.
To view the status of the cable modem initialization:
1. Launch a web browser from a computer that is attached over an Ethernet cable to the
cable modem or from a computer that is connected to a WiFi router that is attached over an
Ethernet cable to the cable modem.
2. Type http://192.168.100.1.
A login page displays.
3. Enter the cable modem user name and password.
The user name is admin. The default password is password. The user name and
password are case-sensitive.
The BASIC Home page displays.
4. Select Cable Connection.
The Cable Connection page displays.
The Startup Procedure section displays the initialization progress.
The Downstream Bonded Channels section displays the status of each channel.
5. To see the Upstream Bonded Channels section and system time, scroll down.
View Cable Modem Status
You can view some basic information about the cable modem.
To view cable modem status:
1. Launch a web browser from a computer that is attached over an Ethernet cable to the
cable modem or from a computer that is connected to a WiFi router that is attached over an
Ethernet cable to the cable modem.
2. Type http://192.168.100.1.

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CM400 High Speed Cable Modem
A login page displays.
3. Enter the cable modem user name and password.
The user name is admin. The default password is password. The user name and
password are case-sensitive.
The BASIC Home page displays.
4. Select ADVANCED.
The ADVACNED Home displays.
The Cable Information pane displays the following:
•Hardware Version. The version of the cable modem model.
•Firmware Version. The version of the cable modem firmware.
•Cable Modem Serial Number. The serial number of the cable modem.
•CM Certificate. The status of the cable modem certificate. If Not installed displays as
the status, contact your cable Internet provider.
For information about using the Reboot button, see Reboot the Cable Modem on page 17.
For information about using the Factory Reset button, see Reset the Cable Modem to
Factory Default Settings on page 18.
View and CLear Event Logs
Event logs capture important cable modem events.
To view and clear the event logs:
1. Launch a web browser from a computer that is attached over an Ethernet cable to the
cable modem or from a computer that is connected to a WiFi router that is attached over an
Ethernet cable to the cable modem.
2. Type http://192.168.100.1.
A login page displays.
3. Enter the cable modem user name and password.
The user name is admin. The default password is password. The user name and
password are case-sensitive.
The BASIC Home page displays.
4. Select ADVANCED > Administration > Event Log.
The Event Log page displays.
The Event Log page shows the following information:
•Time. The time the event log entry was recorded.
•Priority. The severity for the event log entry.

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CM400 High Speed Cable Modem
•Description. A description of the event log entry.
5. To refresh the log page, click the Refresh button.
6. To clear the log entries, click the Clear Log button.
Change the admin Password
You can change the default password that is used to log in to the cable modem with the user
name admin.
To change the password for the user name admin:
1. Launch a web browser from a computer that is attached over an Ethernet cable to the
cable modem or from a computer that is connected to a WiFi router that is attached over an
Ethernet cable to the cable modem.
2. Type http://192.168.100.1.
A login page displays.
3. Enter the cable modem user name and password.
The user name is admin. The default password is password. The user name and
password are case-sensitive.
The BASIC Home page displays.
4. Select ADVANCED > Administration > Set Password.
The Set Password page displays.
5. Type the old password.
6. Type the new password in the Set Password field.
7. Type the new password in the Repeat New Password field.
8. Click the Apply button.
Your change takes effect.
Reboot the Cable Modem
Rebooting the cable modem disconnects all computers from the cable modem’s local area
network (LAN). After the cable modem is finished booting and reestablishes a connection
with the cable provider’s network, the devices reconnect to the cable modem’s LAN.
To reboot the cable modem:
1. Launch a web browser from a computer that is attached over an Ethernet cable to the
cable modem or from a computer that is connected to a WiFi router that is attached over an
Ethernet cable to the cable modem.
2. Type http://192.168.100.1.
A login page displays.

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CM400 High Speed Cable Modem
3. Enter the cable modem user name and password.
The user name is admin. The default password is password. The user name and
password are case-sensitive.
The BASIC Home page displays.
4. Select ADVANCED.
The ADVANCED Home page displays.
5. In the Cable Information pane, click the Reboot button.
A confirmation message displays.
6. Click the OK button.
The cable modem reboots.
Reset the Cable Modem to Factory Default Settings
To reset the cable modem to factory default settings, you can use either the Reset button on
the back panel of the cable modem or the Factory Reset software button. However, if you
changed the default password to access the cable modem and lost the password, you must
use the Reset button on the back panel.
After you reset the cable modem to factory default settings, the user name is admin, the
password is password. The LAN IP address is always 192.168.100.1. You cannot change
this LAN IP address.
Use the Reset Button on the Back Panel
CAUTION:
This process erases all settings that you configured in the cable modem.
To reset the cable modem to factory default settings:
1. On the back of the cable modem, locate the Reset button.
Reset button
2. Using a straightened paper clip, press and hold the Reset button for about seven seconds
until all LEDs blink.
3. Release the Reset button.

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CM400 High Speed Cable Modem
The configuration is reset to factory default settings. When the reset is complete, the
cable modem reboots. This process takes about one minute.
WARNING:
To avoid the risk of corrupting the firmware, do not interrupt the
reset. For example, if you are connected to the web management
interface, do not close the browser, click a link, or load a new page.
Do not turn off the cable modem.
Use the Factory Reset Software Button
CAUTION:
This process erases all settings that you configured in the cable modem.
To erase the settings:
1. Launch a web browser from a computer that is attached over an Ethernet cable to the
cable modem or from a computer that is connected to a WiFi router that is attached over an
Ethernet cable to the cable modem.
2. Type http://192.168.100.1.
A login page displays.
3. Enter the cable modem user name and password.
The user name is admin. The default password is password. The user name and
password are case-sensitive.
The BASIC Home page displays.
4. Select ADVANCED.
The ADVANCED Home page displays.
5. In the Cable Information pane, click the Factory Reset button.
A confirmation message displays.
6. Click the OK button.
The configuration is reset to factory default settings. When the reset is complete, the
cable modem reboots. This process takes about one minute.
WARNING:
To avoid the risk of corrupting the firmware, do not interrupt the
reset. For example, do not close the browser, click a link, or load a
new page. Do not turn off the cable modem.

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3. Troubleshooting
This chapter provides information about troubleshooting your cable modem.
The chapter includes the following sections:
•Use LEDs to Troubleshoot
•Cannot Log In to the Cable Modem
•Troubleshoot the Cable Internet Connection
Note: NETGEAR provides helpful articles and documentation at
support.netgear.com.