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Item#: N82E16825122015

MOTOROLA SB6121 SURFboard Cable Modem Up To 172 Mbps Down and 131 Mbps Up RJ-45, Gigabit Ethernet DOCSIS 3.0, 2.0 and 1.1, Euro-DOCSIS 3.0

  • Gigabit Ethernet connectivity
  • DOCSIS 3.0-certified (EuroDOCSIS 3.0-based)
  • Channel bonding of up to 4 downstream and 4 upstream channels
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SB6121 SURFboard Cable Modem RJ-45

Building upon the success of the SB6120, Motorola's SURFboard SB6121 delivers your complete personal media experience, at lightning-fast broadband speed. It harnesses the power of DOCSIS 3.0 technology to bond up to four downstream channels and four upstream channels - providing you advanced multimedia services with data rates of more than 100Mbps in each direction. That makes gaming, shopping, downloading, working, high-quality voice and video conferencing, and peer-to-peer networking applications far more efficient than ever before.



SB6121 Easy to Set Up and Use
  • Plug-and-play installation
  • Front panel LEDs indicate status and simplify troubleshooting
  • Multi-language user guides
  • Supports standard internet software
  • User-friendly online diagnostics

  • Stylish and space-saving enclosure
  • Offers innovative, high-bandwidth data and multimedia services to customers
  • Backward-compatible to DOCSIS / EuroDOCSIS 1.x and 2.0

Advanced Services Ready
  • DOCSIS 3.0-certified (EuroDOCSIS 3.0-based)
  • Channel bonding of up to four downstream and four upstream channels
  • 1GHz capable tuners
  • Supports IPv4 and IPv6 to expand network addressing capabilities
Versatile and Convenient
  • Compatible with Windows, Macintosh, and UNIX computers.
  • Gigabit Ethernet (RJ-45) data port enable flexible, high-speed connectivity with Auto Negotiate and Auto MDIX

Reliable and Secure
  • Enhanced security: supports Advanced Encryption Services (AES) traffic encryption
  • Remotely configurable and monitorable using SNMP and TFTP

As part of Motorola's DOCSIS 3.0 Ultra-Broadband family of products, the SB6121 includes an enhanced tuner that supports up to a 1GHz downstream input, which allows operators to increase the frequency spectrum for deployment of new high-value service - such as bandwidth on-demand, commercial services, interactive gaming, and IPTV. The SB6121 features a 10/100/1000 Base-T Ethernet (RJ-45) port, as well as intuitive, easy-to-read front-panel operational status LEDs.

What Is DOCSIS 3.0?

With the DOCSIS 3.0 specification, cable Internet providers can take advantage of the extra capacity provided by channel-bonding technology in order to offer ultra-fast broadband services. Channel bonding allows parallel data pipes to act as a single broadband conduit. With each channel capable of providing around 40Mbps of data, the Motorola SURFboard SB6121's four downstream channels can provide a theoretical maximum of 160Mbps of throughput.

Currently, cable providers max out at around 50Mbps of downstream data throughput, but DOCSIS 3.0 will enable cable Internet providers to continue to improve the speed of their networks.

System Requirements
The SB6121 is compatible with the following operating systems:
  • Windows 7
  • Windows Vista, Service Pack 1 or later
  • Windows XP, Service Pack 2 or later
  • Mac 10.4 or later (Ethernet connection only)
  • UNIX (Ethernet connection only)
  • Linux (Ethernet connection only)

What's in the Box

Motorola SURFboard SB6121, Ethernet cable, Installation sheet


Learn more about the Motorola SB6121




Cable Modem
1 x RJ-45, Gigabit Ethernet
Cable Interface
75ohm F-connector
DOCSIS 3.0, 2.0 and 1.1, Euro-DOCSIS 3.0
Max Transmission Rate
Up To 172 Mbps Down and 131 Mbps Up


Data Protocol: TCP/IP

Power: 9W (nominal)

Input Power: 105 to 125 VAC, 60 Hz

-Modulation: 64 or 256 QAM

-Capture Bandwidth: 100 MHz (edge to edge)

-Maximum Theoretical Data Rate:
DOCSIS: 171.537 Mbps (4 channels) / 42.884 (single channel)@ 256 QAM at 5.36 Msym/s
EuroDOCSIS: 222.464 Mbps (4 channels) / 55.616 (single channel)@ 256 QAM at 6.952 Msym/s.

DOCSIS: = 24 MHz
EuroDOCSIS: = 32 MHz.

-Symbol Rate:
DOCSIS: 64 QAM 5.057 Msym/s; 256 QAM 5.361 Msym/s

EuroDOCSIS: 64 QAM 6.952 Msym/s; 256 QAM 6.952 Msym/s.

-Operating Level Range: –15 to 15 dBmV

-Security: DOCSIS 3.0 Security (BPI+, EAE, SSD)

-Network Management: SNMP v2 & v3

-Provisioning Supports: IP addressing using IPv4 and/or IPv6 (dual stack).

-Modulation: QPSK and 8, 16, 32, 64, 128 QAM

-Maximum Channel Rate
DOCSIS 131.072 Mbps (4 channels) / 32.768 Mbps (single channel): @ 128 QAM at 6.4 MHz
EuroDOCSIS 131.072 Mbps (4 channels) / 32.768 Mbps (single channel): @ 128 QAM at 6.4 MHz.

-Channel Width 200 kHz, 400 kHz, 800 kHz, 1.6 MHz, 3.2 MHz, 6.4 MHz

-Symbol Rates: 160, 320, 640, 1280, 2560, 5120 ksym/s

-Frequency Range: DOCSIS 5-42 MHz (edge to edge), EuroDOCSIS and optional DOCSIS 5 to 65 MHz (edge to edge)

Compatibility PC: 90496, Pentium, or later; Windows Vista, 2000, XP or 7 or Linux with Ethernet connection (older versions of Windows, although not specifically supported, will work with this cable modem).
Macintosh: Power PC or later; OS 9 or higher, Ethernet connection.
UNIX: Ethernet connection.
Home Networking: Ethernet router or wireless access point.


Package Contents
Ethernet Cable
Power Supply
Software License & Regulatory Card
Product Guide (Install Sheet)

Manufacturer Warranty

1 Year Limited Warranty
1 Year Limited Warranty

Quick Info


  • Limited Warranty period (parts): 1 year
  • Limited Warranty period (labor): 1 year

Customer Reviews of the Motorola SB6121

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  • Jonathan M.
  • 12/9/2014 11:03:00 AM
  • Tech Level: High
  • Ownership: more than 1 year
  • Verified Owner

5 out of 5 eggsGreat Modem

Pros: Modem was easy to setup with Comcast internet. Noticeable difference with download, upload speed and reliability. compared to modem Comcast makes you pay monthly rent for.

Cons: None

Other Thoughts: Have 50 mbps download and 20 mbps upload Comcast.
Can keep steady speed on when friends over playing games, three of us can download a game at same time and keep a 6-8 MBps speed through steam. (So 15 minutes to download a game)

Did you find this review helpful? Yes No

  • Matthew C.
  • 12/9/2014 7:58:37 AM
  • Tech Level: Somewhat High
  • Ownership: more than 1 year
  • Verified Owner

5 out of 5 eggsIf you're looking to go Docsis 3, get this!

Pros: I purchased this modem to upgrade from 16/5 to 50/20 on Comcrap here in NJ, and this modem consistently gave me 55-60 mbps down and 16-20 up! I've since moved to a new location, across town, and they changed their packages, so I'm now on the 105/15 package, and with this modem I've been able to hover in the 105-115 mbps down and 12-16 up range during speed tests.

Cons: No cons of the modem, just my provider who gives me barely ANY upload speed for all of my download speed. Oh, and constantly drops our connection, slows down to the 20-30 mbps range during the day (stupid shared cable), etc. But that's comcrap's fault, not Motorola's!

Other Thoughts: All tests ran when connected in the following setup: Motorola SB6121 --Gbe--> Netgear WNR3500L v2 (running DD-WRT) --Gbe--> My AMD 8320 8-core, Asus M5A99FX Pro R2.0 PC running either Windows 7 Ultimate x64 or OpenSUSE 13.1 KDE.

1 out of 1 people found this review helpful. Did you? Yes No

  • David G.
  • 11/30/2014 5:34:00 PM
  • Tech Level: Somewhat High
  • Ownership: 1 month to 1 year
  • Verified Owner

5 out of 5 eggsAmazing Modem

Pros: Amazing reliable modem. It is currently connecting the Netgear Nighthawk AC1900 router and it's doing an amazing job. My old modem blocked port forwarding for some reason and this one does it straight out of the box.

Cons: No cons.

Other Thoughts: Highly recommend this reliable modem.

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  • Thomas H.
  • 11/29/2014 7:32:34 AM
  • Tech Level: High
  • Ownership: 1 month to 1 year
  • Verified Owner

2 out of 5 eggsearly death

Pros: Worked fine.

Cons: Died > 30 days after purchase so New Egg won't RMA it, so repair is the responsibility of the manufacturer. Motorola/Arris web site is set up for telecoms, not people. If they RMA it, turnaround time will be up to a month.

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  • Atul S.
  • 11/27/2014 12:45:27 PM
  • Tech Level: High
  • Ownership: 1 month to 1 year
  • Verified Owner

5 out of 5 eggsWorks with Comcast

Pros: Works as expected with Comcast. I had a DOCSIS 2 modem, and Comcast was sending me not-so-subtle reminders to upgrade the modem to DOCSIS3. Bought this to satify comcast. I've had it for about a month now, an it is working as expected. I have 25mbps connection so I havent tested the upper end of this modem's capability, but it works just fine at this bandwidth.

Cons: LED's are very bright.

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  • 11/24/2014 12:59:02 PM
  • Tech Level: High
  • Ownership: 1 week to 1 month
  • Verified Owner

5 out of 5 eggsexellent

Pros: docsis 3.0 no drops so far

Cons: no cons

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  • Grady B.
  • 11/23/2014 3:30:24 AM
  • Tech Level: Somewhat High
  • Ownership: 1 month to 1 year
  • Verified Owner

5 out of 5 eggsgreat unit

Pros: I bought this unit so I don't have to pay fees to my broadband provider. This unit has worked with no issues.

Cons: None

Other Thoughts: It will blow your ISP's mind that you want to use your own modem, so it makes it a little hard to get them to set it up.

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  • George F.
  • 11/19/2014 10:21:06 PM
  • Tech Level: High
  • Ownership: 1 month to 1 year
  • Verified Owner

5 out of 5 eggsWorked fine with Comcast and TWC

Pros: * Very simple cable modem with decent web access (on LAN side) to check the configuration.
*Front panel light indicators, once you understand the symbols, helps with troubleshooting.

Cons: * Cannot upgrade the firmware ... this is supposed to be handled by the ISP (Comcast)
* Use short quad-shielded RG-6 to ensure proper connectivity. Seems to be sensitive to type of coaxial cable used for WAN connection.

Other Thoughts: This is my second SB6121 in 2.5 years. My first one was for Time Warner Cable as my ISP, and it worked flawlessly. I gave that to a work colleague, and then I moved into Comcast country, so I purchased the same SB6121. Worked fine with the Cisco RV110W firewall.

1 out of 1 people found this review helpful. Did you? Yes No

  • Jonathan L.
  • 11/19/2014 1:18:49 PM
  • Tech Level: Somewhat High
  • Ownership: 1 month to 1 year
  • Verified Owner

5 out of 5 eggsWorks like it should

Pros: Took one call to TWC to get it activated and I haven't thought about it since then. Works the way it's supposed to. Unobtrusive black housing.

Cons: It's not free, but it's not expensive in the long run.

Other Thoughts: Saving the $6/month TWC was charging to use their modem, this will pay for itself in less than a year. Good deal in my book.

Did you find this review helpful? Yes No

  • Samantha H.
  • 11/17/2014 8:28:00 AM
  • Tech Level: Somewhat High
  • Ownership: 1 day to 1 week
  • Verified Owner

5 out of 5 eggsUpgraded from SB5120 w/ Comcast - DL speed doubled!

Pros: Did not need to call comcast to activate, just plugged it in, rebooted my router and surfed to where my new hardware was automatically identified and configured.
I ran on three networked computers before and after the install. My two older machines showed no change, as they are too old to handle the 33mb/s download speed my main system was alrerady pulling. My Main box jumped from 33mb/s downloads to 59.53 mb/s! Yay for DOCSIS3! Ping dropped about 2 to 4 ms on each machine as well.

Cons: None yet

Other Thoughts: It's just day one, so time will tell, but it's looking good so far. Also, I am subsribed to the Comcast Boost service, so IDK what impact that may have on my numbers. I know it was not supported by my old Motorola surfboard.

1 out of 1 people found this review helpful. Did you? Yes No

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Item#: N82E16825122015
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