Motorola SURFboard SB6121 Quick Reference Guide

Motorola SURFboard SB6121 Quick Reference Guide

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Motorola SURFboard SB6121 Quick Reference Guide



Motorola's DOCSIS 3.0 Modem includes a number of major enhancements including channel bonding and IPv6. Motorola's DOCSIS 3.0 modems support DOCSIS 1.x, 2.0, and new 3.0 features.

DOCSIS 3.0 provides a number of enhancements earlier versions of DOCSIS, but most notably, channel bonding. Channel bonding enables multiple downstream and upstream channels to be "virtually-bonded" together to be used by a single subscriber. This increases downstream speeds up to 1 Gbps, and upstream throughput up to a minimum rate of 120 Mbps. Additionally, DOCSIS 3.0 supports IPv6and Internet Protocol Television (IPTV).

IPv6 greatly expands the number of Internet addresses that operators may use.

This document was developed to assist all Technical Operations employees with the proper steps of installing, configuring, and troubleshooting the Motorola SB6121 modem.


The serial number and equipment address can be found on the bottom of the modem. These items will need to be entered into CSG in order for the gateway to operate.

CSG Field Motorola SB6121 modem

Additional Warehouse Information

CSG Equipment Type: M1

CSG Equipment Model: SB6121

CSG Equipment Mode: 0

Installation Procedure

Connect one end of the power adapter into the modem and the other end into power outlet or surge protector.

Connect an active coax cable.

Connect the primary computer to Ethernet port on the modem using a Cat 5 Ethernet cable.

Do not set the modem in an enclosed area, near large appliances, UPS (uninterrupted power supplies), microwaves, computer monitors or 2.4GHz cordless phones.

Rear Panel Connections

  1. An RJ-45 Ethernet port to connect the modem to the computer
  2. F-connector connects to an active cable drop
  3. Connects the modem to the power adapter

Front Panel Display

The front panel LEDs should be used during installation, configuration, and troubleshooting. Use them as a visual reference for how and what the modem is performing.

Front Panel Display

Key Light Off Flashing On
1 POWER Power is disconnected This light should not flash Green: Power is properly connected
2 RECEIVE Receive channel not found Scanning for a receive (downstream) channel Green: Downstream channel is connected
Blue: Downstream channel is connected with bonded channels
3 SEND Send channel not found Scanning for a send (upstream) channel Green: Upstream channel is connected
Blue: Upstream channel is connected with bonded channels
4 ONLINE Internet connection failed Scanning for configuration parameters Connected to the Internet
5 LINK No connection to the SB6121 Ethernet port is detected Transmitting or receiving data on the Ethernet port Amber: A device, computer, or hub is connected via the Ethernet (10Base-T) or Fast Ethernet (100Base-T) port
Blue: High-speed Gigabit Ethernet connection to the
6 Power Powers on and off the cable modem
During normal operation, the POWER, RECEIVE, SEND, and ONLINE lights are ON. The LINK light flashes when the cable modem is transferring data.

Start-Up Sequence

The SB6121 goes through a series of steps when first connected to power and RF signal.

The SB6121 start-up steps are:

  1. Power On Self Test (POST). If LED remains off, modem is faulty.
  2. Scanning downstream frequencies.
  3. Scanning upstream frequencies.
  4. Downstream and upstream acquired. Modem processing for DHCP, TFTP, and TOD.
  5. Ready. PC/Activity is solid when a CPE is connected and blinks when transmitting or receiving data.
  6. Powered off.
  7. Modem is successfully registered but Network Access Control (NACO) is disabled via DOCSIS® configuration file.
  8. Performing firmware upgrade

DOCSIS 3.0 modems have dual-colored LEDs to visually determine if channel bonding and Gigabit Ethernet is enabled.

Troubleshooting Tips

Rule out RF

Use the front panel LEDs as well as a SLM to rule out potential signal issues. If the RF levels are acceptable, most issues can be corrected by restarting the cable modem. To restart the Motorola SB6121:

  1. Shutdown the computer
  2. Unplug the cable modem from power and wait approximately 1 minute.
  3. Plug the cable modem back into power.
  4. Observer the LED light up sequence as detailed above.
  5. Restart the computer.

LEDs and Error conditions

Light Turns off during Startup: Turns off during normal operation:
RECEIVE The downstream (RECEIVE) channel cannot be acquired. The downstream channel was lost.
SEND The upstream (SEND) channel cannot be acquired. The upstream channel was lost.
ONLINE IP registration was unsuccessful. IP registration was lost.
POWER Verify the power connection. Verify the power connection.

Troubleshooting Tips

  • Release and Renew the IP address on computer if its unable to access the internet or the modem's setup page
  • Reboot the computer
  • Disable the proxy settings in the computer's web browser, and temporarily disable any firewall software during the setup of the gateway.
  • Always use straight-through cables, not cross over cables

User Guides, Drivers, and Datasheets can be found at:


Motorola SURFboard SB6121 Unboxing, Review Speed Test Video

Documents / Resources


Download manual

Here you can download full pdf version of manual, it may contain additional safety instructions, warranty information, FCC rules, etc.

Download Motorola SURFboard SB6121 Quick Reference Guide


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