2 Replies Latest reply: Oct 6, 2009 11:30 AM by marengo
marengo Level 1 Level 1 (10 points)
I have a large home computer network. And I would like to not have to modify the downstream hardware much. I would like to see the following hardware working together...

Comcast cable internet {CC} DHCP
Motorola Surfboard SB6120 modem {SB}
Apple Airport Extreme (802.11n) {AE}
Computers running MacOS 10.4, 10.6 and Windows XP

The one setup recommended by Motorola that should work is hooking up an open switch directly the SB. But I would like a bit more of a barrier with controls limiting outside access to an open modem. I’m trying to get something to work and specifically the AE to follow the SB.

The SB is a pretty much plug and play box that does not have a lot of controls. It worked with a single computer. This was tested. The difficulty begins when adding a router like the AE. Choosing the configuration for the incoming data 1) manually or 2) through DHCP. Manual input is not an option. I couldn’t get the AE to pull the necessary information from the SB6120 to operate. Motorola support said that the SB is just too underpowered to a router following it. What? Options for sharing the connection are 1) Share a public IP address 2) Distribute a range of IP addresses or 3) Off (Bridge Mode) – which is supposed to take advantage of the SB’s capability of distributing IP addresses.

The combination that seems like it should work is setting collecting the incoming coax information to be collected by DHCP. Then share the public IP address with DHCP and NAT. No bananas on this one. Running with the incoming IP information collected by DHCP has missing information and does not pass the CC data along.

I’ve tried all the options for the AE and none seem to function correctly. Should I give up and replace it with a switch? I do like having the control of limiting access and different firewall controls. That gets lost if I cannot use a router after the SB.

Has anyone succeeded in a functional setup? Or is there a good plan of attack that I haven’t tried. I’ve used the options that are available to me, or have I?

As a cable modem to a direct computer, the SB is many times faster than my SB5100. I get almost 10 Mb/s upload and 20Mb/s download with the new box. I would really like to see this work.

Mac Mini(s), Mac OS X (10.6.1), Windows XP sp3 in mix
  • William Boyd, Jr. Level 6 Level 6 (10,515 points)
    marengo wrote:
    I have a large home computer network. And I would like to not have to modify the downstream hardware much. I would like to see the following hardware working together...

    Comcast cable internet {CC} DHCP
    Motorola Surfboard SB6120 modem {SB}
    Apple Airport Extreme (802.11n) {AE}
    Computers running MacOS 10.4, 10.6 and Windows XP

    The one setup recommended by Motorola that should work is hooking up an open switch directly the SB. But I would like a bit more of a barrier with controls limiting outside access to an open modem. I’m trying to get something to work and specifically the AE to follow the SB.


    Choosing the configuration for the incoming data 1) manually or 2) through DHCP.


    DHCP is the right choice.

    Motorola support said that the SB is just too underpowered to a router following it.


    I agree with you that such a comment sounds like nonsense.

    Options for sharing the connection are 1) Share a public IP address


    This is the option you want.

    3) Off (Bridge Mode) – which is supposed to take advantage of the SB’s capability of distributing IP addresses.


    I looked at Motorola's documentation for your modem and didn't see anything about that.

    When switching between connecting a computer to your SB and connecting your AirPort Extreme, be sure that you cycle power on the SB so that it can reassociate with the other unit.
  • marengo Level 1 Level 1 (10 points)
    I went through the process again as William suggested. Right on the money. I'm a bit surprised with Motorola support, but this hitch only held up the transfer for a day.