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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

2 Year Limited Warranty
2 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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  • 9/16/2014 4:45:17 PM
  • Tech Level: Somewhat High
  • Ownership: more than 1 year
  • Verified Owner

1 out of 5 eggsArris Problems

Pros: Used to work OK.

Cons: Since Arris purchased Motorola Home models SB6120, SB6121 and SB6141 have been plagued with T3 and T4 timeouts that cause frequent modem reboots. My ISP, Mediacom, asked me if I would be willing to test a reworked modem to help solve the problems. Instead I went with another brand.

Did you find this review helpful? Yes No

  • Robert A.
  • 9/15/2014 8:14:42 AM
  • Tech Level: Somewhat Low
  • Ownership: less than 1 day
  • Verified Owner

5 out of 5 eggsWanted a new SurfBoard - DOCSIS3

Pros: This is my thrird Motorola SurfBoard since my self-installation when getting the cable internet and TV was upgraded in this area by the monpoly which is Comcast. I have never paid their leasing charges in these ten years or so. They charge seven or eight dollars a month here for a cable modem - so, this new, faster,more capable modem will "pay for itself" in a few months. Each Motorola SurfBoard has not given me a bit of trouble. I wanted to upgrade to DOCSIS 3 because the Motorola SurfBoard SB5101 I have used for the last five years was "end of life" as DOCSIS 2. I like the black housing and subtle blue connectivity lights which are not bothersome or intrusive. The modem is now branded as Arris - as well as Motorola. I suppose there was a merger. Bottom line: this is a great modem and it works! I will return here to update my review if it fails in any way. This modem is not only on Comcast's approved list, it has a three star rating, which, according to Comcast, is "the highest and most thorough level of testing."He had to call the "office" to activate the internet service. Xfinity's internet speed test site states that I am getting 28 to 30 Mbps downloads and the upload speed is between 5 and 5.8 Mbps. I've gotten similar values with two other internet speed testing sites. Set up took just under 15 minutes - this includes plugging it in, attaching the cable and the router, and giving Comcast tech a phone call to provide my account number, etc., modem brand and model number (on approved list) serial number and the modem's ID number. The modem was activated by them, and handles all effortlessly. I'm really pleased with this modem, as I have been with the other Motorola cable modems I have owned, and expect it to serve me well. I will not pay xfinity-Comcast any more each month if I can help it. They have given me no problems about this - maybe they know I will show up at the local office to be a pain if they make any "mistakes" on my billing.

Cons: None

Other Thoughts: I ordered this from Newegg and received it via USPS with no shipping charge in 24 hours. I ordered from Newegg after searching the big stores on the internet and shopping for the best price, availablity and shipping cost I could find.

Did you find this review helpful? Yes No

  • Eric W.
  • 9/15/2014 7:51:22 AM
  • Tech Level: High
  • Ownership: 1 month to 1 year
  • Verified Owner

5 out of 5 eggsSuper Solid

Pros: Super solid, reliable, dependable, fast, handles multiple upload - download streams with ease. Bought this when Comcast upgraded cable internet speeds; plugged it in, registered with the Matrix, off to the races - no problems whatsoever.

Cons: none

Other Thoughts: Motorola makes solid hardware - my last surfboard modem had five years of continuous heavy use with not one hitch.

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  • Yu-I T.
  • 9/13/2014 5:59:21 PM
  • Tech Level: Average
  • Ownership: 1 day to 1 week
  • Verified Owner

5 out of 5 eggsDoes the job well/

Pros: I purchased this modem which is a DOCSIS 3.0 modem. It worked. I went from a 25mbps download speed to over 50mbps. What a difference.

Cons: none

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  • Michael H.
  • 9/10/2014 7:26:16 AM
  • Tech Level: Somewhat High
  • Ownership: 1 month to 1 year
  • Verified Owner

5 out of 5 eggsHooray for not being charged to rent a modem.

Pros: It works great.

Cons: Comcast struggled mightily to get it set up initially, but that's their fault. They had to send a technician out to check something in the wall and test the line. They got it to work eventually, but again, the problem was theirs, not the modem's.

Other Thoughts: I'm delighted to pay this modest up front cost rather than paying $8 every month to Comcast.

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

  • Anonymous
  • 9/8/2014 7:08:27 PM
  • Tech Level: High
  • Ownership: 1 day to 1 week
  • Verified Owner

5 out of 5 eggsPerfect!

Pros: Simple
Looks Good
Reliable (So Far)

Cons: Lightweight
Too Bright

Other Thoughts: Had this for a week and havent had anyconnection issues at all. Saved $8 a month using this instead of renting the old modem from comcast.

Did you find this review helpful? Yes No

  • Isaac L.
  • 9/5/2014 4:02:35 PM
  • Tech Level: Somewhat High
  • Ownership: 1 month to 1 year
  • Verified Owner

5 out of 5 eggsGreat deal

Pros: Great deal for those wanting a DOCSIS 3.0 modem and save themselves some money on cable modem rental fees.

Cons: Not the latest technology. This isn't necessarily a con unless you need to spend the additional money for higher performance.

Other Thoughts: Best DOCSIS 3.0 modem available for those looking to save themselves some money and don't have particularly demanding use cases.

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  • Adam M.
  • 9/4/2014 8:30:08 AM
  • Tech Level: Somewhat High
  • Ownership: 1 month to 1 year
  • Verified Owner

4 out of 5 eggsSolid Buy

Pros: Purchased this for my father and have been satisfied with its performance. Fast and reliable.

Cons: None

Other Thoughts: Can't go wrong with Surfboard Modem, been using them since day one all the way back to 1999.

Did you find this review helpful? Yes No

  • Jaichandran M.
  • 8/28/2014 11:49:33 AM
  • Tech Level: Somewhat High
  • Ownership: 1 month to 1 year
  • Verified Owner

5 out of 5 eggsWork really well and super fast.

Pros: Before purchasing this one, I was using a first generation Motorola modem with for an internet speed of 50 mbps. When I did the speed test it was giving just half of the speed for a wired connection and 1/4th for wireless. I researched and found that would have to change modem in order to get full speed that was delivered by ISP. I purchased this one and as expected , it delivered full speed of 50 mbps and sometimes more than that. Works well, still in use. No issue observed. Very easy to install and cool looking lights.

Cons: None

Other Thoughts: I am getting throughput > 50 Mbps as it is a high throughput modem.

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

  • Robert A.
  • 8/27/2014 7:42:36 AM
  • Tech Level: Somewhat High
  • Ownership: 1 month to 1 year
  • Verified Owner

4 out of 5 eggsWorks Well

Pros: It is a high throughput modem. It pays for itself instead of going through Comcast rental fees. The cable tech was able to get it setup right away right out of the box.

Cons: I do have to reboot it about once a month, since I loose connection to the internet sometimes.

Other Thoughts: I am getting throughput > 50 Mbps. And If I want to upgrade my internet speed I can go up one more plan without upgrading my modem, but needs more than 50Mbps?

Did you find this review helpful? Yes No

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Item#: N82E16825122015
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