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Level 1

1 points

Connecting Motorola SB6121 Cable Modem and AirPort Extreme

I moved into a new house a couple of days ago so of course the first thing that I needed to do was get the home wireless up and running. My ISP is through Comcast. I purchased my own cable modem (Motorola SB6121) instead of renting and used my own AirPort Extreme as the wireless router.

First, if you're purchasing your own cable modem, you will need to contact your ISP and provide them with the HFC MAC ID on the cable modem. Once you've gone through the motions, you will be able to connect your Mac (in my case Macbook) directly to the modem via ethernet cable and access the internet.

Issue:

When I connected the SB6121 to the AE, I could connect wirelessly to the AE, but I did not have access to the internet. So, basically the SB6121 and the AE were not talking to each other despite being physically connected via ethernet cable.

Solution:

After days of searching for online answers and forums (and trying different solutions) I was able to successfully get everything up and running. Make sure that you have 2 ethernet cables available.

Here are the steps.

I restored my AE to factory settings just to keep everything simple. Here are instructions: http://support.apple.com/kb/HT3728 Once you've restored your AE, make sure that both the AE and the cable modem are unplugged from their power sources.
Plug in the power to the SB6121.
Connect your SB6121 directly to your laptop via Ethernet cable. Test to ensure that you have internet accessibility by going to any website.
Remove the ethernet cable from your laptop and plug it into the "internet in" jack in the back of the AE.
Power up the AE.
Connect your laptop to the back of the AE using ethernet cable #2.
Launch a browser. You should now be able to successfully connect to any website.
Assuming that you reset your AE to factory settings, it should just be broadcasting the generic "Airport Extreme" SSID. Disconnect the ethernet cable and connect using wireless to the SSID. Launch a browser and you should be able to connect to the internet.
You can now use the AirPort Utility to configure the AirPort settings.

I assume that this solution would work with any of the base stations.

AirPort Extreme (4th Gen)-OTHER

Posted on Apr 9, 2012 8:12 AM

40 replies

May 9, 2014 3:48 PM in response to Instigator10219

I tried every which way but loose with the Motorola SB121 Modem I had. Including every option on this thread and a few others. Wasted half a day. The only thing that worked for me was getting the Zoom 5341 modem and resetting my Airport Extreme to factory defaults and having it reconfigure the modem.

So I concure. Motorola + Airport = Nightmare.

EL1001

Level 1

0 points

May 31, 2014 11:32 AM in response to Yodabeesh

Great instructions. I had the same issue. Being connected to the ethernet cable was the key. Thanks for posting.

Jul 14, 2014 3:25 PM in response to Yodabeesh

I have a network with an older airport extreme and two imacs, two windows laptops and two rokus. I replaced my old modem with the motorola sb6121. I simply unplugged the cable line and the line to the AE and plugged those lines into the motorola. One of the imacs was on, so I opened the browser and there was the Xfinity page. A few minutes later and the system was running as before, both wireless and ethernet connections.

Sep 19, 2014 5:32 AM in response to anothercomputerguy

Thanks, if you see this. I've been updating an iBook (dual USB, translucent) to 10.4.11, as well as preparing an identical model replacement for my 1.5GHz PPC powerbook and somewhere along the line I screwed up settings with the Time Capsule. Only could get to pass thru one IP address to MacBook Pro, if I woke the new powerbook from sleep, that caused the internet connection to drop.

After a soft reset of TC, I wrote over the same password, saved & quit Airport Utility. Followed with modification:

a) connected Ethernet cable from CABLE MODEM to MacBook Pro confirmed working IP and without the airport (Wi-Fi only had 169. self-assigned anyway)

b) POWER OFF THE CABLE MODEM

c) POWER OFF THE TIME CAPSULE

d) POWER ON THE TIME CAPSULE

connected Ethernet cable from Modem to Time Capsule

connected Ethernet cable from Time Capsule to MacBook Pro

e) POWER ON THE CABLE MODEM

Ethernet is currently active and has the IP address 10.0.1.2.

Using DHCP

Wi-Fi is connected to Eyes Only Network and has the IP address 10.0.1.5.

The simplest solution with the fewest steps is why I love it. :-)

logic368

Level 1

4 points

Jan 16, 2015 2:23 PM in response to Yodabeesh

Hi Everybody!

I might have figured out an EASIER way to get the SB6121 to work well with an Apple Airport:

Just change the Airport settings to:

Router Mode: DHCP and NAT

And THEN (important): click Network Options and UNCHECK Enable NAT Mapping Protocol.

Apply the settings, and this should work wonderfully! Obviously, don't forget to power cycle both devices after applying settings.

At least this worked for me (Time Warner Cable, SB6121, Airport Time Capsule 6th Gen, Firmware 7.7.3).

Good Luck!

Jun 26, 2015 10:16 PM in response to Yodabeesh

any thoughts on connecting an ADT pulse security system? Mine worked just fine with ATT before I just got Comcast, but the old ATT modem had multiple ports I could use, the Motorola Surfboard only has one, which goes to the airport express.

Sep 26, 2015 1:52 AM in response to artmiller

In migrating from AT&T DSL to Comcast, I had trouble with my Airport Extreme (AE) Router and an Arris SURFboard SB6183 Cable Modem.

Artmiller's steps worked for me:

Reset the AE to factory settings by pushing a paper clip into the small hole in the back. Hold it for ~20 seconds.
Connect MODEM directly to COMPUTER and confirm network connectivity
POWER OFF THE CABLE MODEM
POWER OFF THE AE ROUTER
Connect the Ethernet cords: Modem to Router, Router to Computer
POWER ON THE ROUTER
POWER ON THE CABLE MODEM

Other settings:

* Allow Setup Over WAN - OFF

* Connect Using DHCP

* Comcast DNS address is 75.75.75.75 - should set automatically

* Internet Options: IPv6 Connection Sharing - OFF

* Network: DHCP and NAT

* DHCP Range is 10.0.1.2 to 10.0.1.200

* Network Options: I did not turn off NAT Port Mapping

Both Internet and Router Lights are Green in the AirPort Utility App.

~3 hours of hassle, and no help from Comcast!

Mitch 751

Level 6

11,624 points

Sep 30, 2015 2:03 AM in response to Woodman72265

I had the same problem, and talked to Telstra the ISP company last night. They have tried remotely to do set up but still failed (after three hours).

This morning :

1. I powered down the cable modem, the switch box for 5 minutes,

2. reset the Time Capsule to factory setting.

3. connect the cable between the ethernet box with TC, switched on the cable modem and switch box.

4. Use the iPad to do the setup instead of iPhone

within a minute, green light and BINGO

Nov 11, 2015 11:22 PM in response to anothercomputerguy

Thanks! Just worked for me! Spent 2 hours before i tried this. You are life saver ..........

Oct 7, 2016 1:29 PM in response to Yodabeesh

Thank you, thank you, thank you!!! I just switched to Wave broadband and my Airport Extreme 802.11ac wasn't connecting to my new SB6141. Even the Wave technician couldn't figure it out. After much frustration (and a couple of hours) I finally found this thread, followed the steps outlined above and voila!, it works.

Connecting Motorola SB6121 Cable Modem and AirPort Extreme