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Cable Modem configuration question
#258445 04/27/09 05:53 PM
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I am replacing DSL with Comcast cable modem. Installation is set for tomorrow.

Currently, the DSL modem (Cisco 678) sits between my router (D-Link WRT54G) and the world. I want to simply replace that appliance with the Motorola SB5101 cable modem.

The SB5101 instructions seem to indicate that it requires a dedicated USB connection. Because of where all this stuff is located, I don't really have any interest in having it hooked up to a computer via USB all the time.

I kind of figured that the USB connection was only for setup (like the serial connection on the cisco) and that - after you've got everything "done" - you can disconnect the USB and just enjoy your bandwidth.

I don't see how I'd access the cable modem when my router is already 168.1.0.0 (or whatever) on my network.

So, I guess my question for those of you with cable modem access is - are you required to have a perpetual USB connection to the cable modem?

The answer could dramatically affect "where" I have the copper installed.

Thanks for your help.


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Re: Cable Modem configuration question
tomtuttle #258456 04/27/09 06:31 PM
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Nope. Mines a Moterolla SB5100. I see there is a usb port on the back, but I've never used it for anything. Don't know what its for.


Fred

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Re: Cable Modem configuration question
tomtuttle #258458 04/27/09 06:33 PM
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Our service is DSL but a quick peek at the FAQ for this modem says you can use USB or up to 100MB Ethernet. You should be fine plugging it by Ethernet directly into your router.

I didn't dig deep enough to definitely answer your second question but it should not be a problem. It may pass on a 'real' Internet address that your router will 'route' to your local 168 network. If not you may have to tweak a bit but the setup looks like it will walk you through this step.

Last edited by Murph; 04/27/09 06:39 PM.

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Re: Cable Modem configuration question
fredk #258459 04/27/09 06:34 PM
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Cool, Fred, thanks.

Do you have the Ethernet cable from the SB5100 attached to a router, then?


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Re: Cable Modem configuration question
tomtuttle #258461 04/27/09 06:40 PM
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Andrew also says, "your Welcome"....

heh heh, Kidding!


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Re: Cable Modem configuration question
Murph #258466 04/27/09 06:55 PM
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Yes, Andrew, thank you as well! Apparently, you and I hit "send" at about the same time; you message was not yet visible to me when I replied to Fred's post.

So, "Thank's" ;\)


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Re: Cable Modem configuration question
tomtuttle #258469 04/27/09 07:02 PM
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I'm running ethernet to a linix firewall box. Its not a real network yet, but its the same thing.

When I originally got this, the cable company set it up. I remember them asking how I wanted the box hooked up to my computer. I just chose ethernet. Since the only other connection on the back of the modem is USB, that must have been the other choice.


Fred

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Blujays1: Spending Fred's money one bottle at a time, no two... Oh crap!
Re: Cable Modem configuration question
fredk #258474 04/27/09 08:02 PM
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Here's your new modem.

It has both a USB port and an ethernet jack. This is pretty common on both DSL and Cable modems. You'll use the ethernet port to connect to your DLink router, just as you do now with the DSL. Your DLink should continue doing exactly what it has been doing. It shouldn't need to change, unless it's some bizarre case of being incompatible with the cable modem.

I'm not sure of the specifics of your situation, but you may have to adjust some of the settings in the DLink so that it will be able to 'see' the Internet. The last time I had a cable modem, if I remember correctly, my router was set up in a more-or-less 'Automatic acquire' mode for the WAN connection (router's connection to the Internet). It grabbed the DNS & gateway info automatically. With my DSL modem, this had to be changed to a 'PPPOE' connection where the router supplies a Username/password to the modem for the connection to my DSL provider's (Verizon) network.

The tech guy doing the install ought to be able to help you with this setup.

The UBS ports on the back of these things are for networking without a network. For situations where a customer doesn't have a router. You can plug these modems directly into a PC/Mac with a USB cable and it'll provide an internet connection. With a router, you wouldn't be using this feature. But with some modems (my DSL modem for instance), it's also the only way to directly configure them and/or do firmware updates.

When I had a cable modem, I never had to do anything with the cable modem itself other than plug it in; AC, Cable, ethernet to router. All of the settings that mattered were done to my router's config settings.

Good luck!

Last edited by PeterChenoweth; 04/27/09 08:13 PM.

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Re: Cable Modem configuration question
PeterChenoweth #258479 04/27/09 08:29 PM
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Whew! Thanks so much, gentlemen. I'm going with Plan A until further notice.


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Re: Cable Modem configuration question
tomtuttle #258503 04/28/09 12:45 AM
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Comcast is evil.



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