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NetFixer
From My Cold Dead Hands
Premium Member
join:2004-06-24
The Boro
Netgear CM500
Pace 5268AC
TRENDnet TEW-829DRU

2 edits

1 recommendation

NetFixer to WiFu

Premium Member

to WiFu

Re: Comcast CS cannot configure SB6141 to bridge mode?

said by WiFu:

I have my own SB6141, which I bought from the recommended list of modems for my comcast internet. It was installed by them and has been working well enough for a few months. I finally got around to trying to configure it, because it is acting as a DHCP server, but I have my own router/firewall/vpn device that I want to use. I come to find out that there is nothing configurable from the modem's management webpage.

I want to set it to bridge mode. Is that setting being locked by comcast's remote configuration of my modem?

Has anyone been successful getting them to change this? I called customer service, but their tactic was to ask me what I want to do with bridge mode. Then they say, no you can't do that, because you have a dynamic IP address, not static. I know the service gives me single dynamic address, that's all I am trying to get. Right now, I have no public IP address I can use!

This change wouldn't affect them at all. They can let me worry about the limitations of VPN and webserver with a dynamic address, but I can't tell if they're clueless, or if they are just refusing to help. "Call the manufacturer" sounds more like the later.

Any suggestions would be welcome. It does look like I can factory reset the modem if it comes to that, but then I might have real problems, whereas right now my only problem is their customer service.

Thanks.

Uhh, the SB6141 is a standard (AKA bridge) modem; that is the only mode of operation that it has. The DHCP server in the SB6141 only operates when the modem is not connected to the Comcast network; it does not have any effect on normal operation using the SB6141 as a media converter/bridge device. Also, with a typical single public IP address residential account, you should only have one device connected directly to the SB6141; that device would be your router's WAN interface, so that no other devices on your network would even be able to see the DHCP server on the SB6141.

Exactly what kind of problem (if any) are you having that you think that putting your SB6141 into "bridge" mode will fix?

FWIW, my SB6121 also has a built-in DHCP server, but even though I have a business class account, and have multiple devices attached to the SB6121, its internal DHCP server in no way interferes with any device I have behind it getting its proper public IP address (nor does it in any way interfere with the public visibility of any services I offer from behind it).




For further clarification, show below are the setup and status screens from each of the three routers that I currently have connected behind my SB6121. As you can see, each of the routers connect to the Comcast network with no interference from the built-in DHCP server in the SB6121.


Netgear WNR1000 WAN setup



Netgear WNR1000 Status



D-Link DIR655 WAN setup



D-Link DIR655 Status



D-Link EBR2310 WAN setup



D-Link EBR2310 Status


I suspect that your problem is just that you don't understand that you absolutely must use Cocmast's DHCP server to assign the public IP address(es) to any equipment that is connected to their network. Hopefully the setup screens shown above will illustrate to you that this is not a problem, it is just the way that things work in the real world.
dealhunter0
Premium Member
join:2005-03-29
Fremont, CA

dealhunter0

Premium Member

I am having problems with having a Linksys E2000 router to get an IP address from a white SB6141 modem (bought from Newegg). It sounds like some kind of DHCP related problem with the cable modem. If I connect a laptop directly to SB6141 then internet works but not with Linksys E2000.

Am I supposed to make any changes to the SB6141 configuration to get it to work? Any pointers will be appreciated.

thanks
mrschultz02
join:2007-09-10
Wallingford, PA
Asus RT-AC88

mrschultz02

Member

said by dealhunter0:

I am having problems with having a Linksys E2000 router to get an IP address from a white SB6141 modem (bought from Newegg). It sounds like some kind of DHCP related problem with the cable modem. If I connect a laptop directly to SB6141 then internet works but not with Linksys E2000.

Am I supposed to make any changes to the SB6141 configuration to get it to work? Any pointers will be appreciated.

Power cycle the modem when ever you plug a different device into it. It grabs the MAC address of what ever is plugged in when it powers up (or the first device plugged in after power up) and remembers it until the next power cycle.
dealhunter0
Premium Member
join:2005-03-29
Fremont, CA

dealhunter0

Premium Member

I tried all possible combinations of power cycling / rebooting both cable modem and router but nothing worked. Linksys router could not get an IP address from SB6141 but my laptop could.

This thread has some discussion about DHCP related issues, and I wonder if I need to change any configuration of the modem to get this to work.

thanks again.
mrschultz02
join:2007-09-10
Wallingford, PA
Asus RT-AC88

mrschultz02

Member

said by dealhunter0:

I tried all possible combinations of power cycling / rebooting both cable modem and router but nothing worked. Linksys router could not get an IP address from SB6141 but my laptop could.

This thread has some discussion about DHCP related issues, and I wonder if I need to change any configuration of the modem to get this to work.

thanks again.

Like others said to the OP, there's really nothing to change on the modem. It must be a router issue, if it has the option to do MAC cloning you might try setting the mac address on the router to the same one as your laptop and see if that works.
dealhunter0
Premium Member
join:2005-03-29
Fremont, CA

dealhunter0

Premium Member

Cloning the mac address fixed the problem.

appreciate the help.

thanks again.