multiple cable modems on a single coax

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bwana

Regular Contributor
So I have comcast with a cable modem. The cable comes into my house and I have a splitter in the basement. One cable run goes to the first floor and another goes to the second floor. The modem from comcast is on the first floor. I want wired ethernet access on the second floor. My idea is to just buy another cable modem (surfboard?) and hook it up on the second floor cable. Will this work? Or does comcast somehow know each and every cable modem in its network? I was poking around the interface of the comcast modem and there is a utilities tab. In this tab is a button that says 'ISP only' Clicking this button brings up a dialog with 'password of the day'. Are these the settings that the cable guy has to set so the modem works? Since I already pay comcast for one modem, shouldnt I be able to add as many modems as I like to the line? I actually want separate wired LANs.
 

CaptainSTX

Part of the Furniture
So I have comcast with a cable modem. The cable comes into my house and I have a splitter in the basement. One cable run goes to the first floor and another goes to the second floor. The modem from comcast is on the first floor. I want wired ethernet access on the second floor. My idea is to just buy another cable modem (surfboard?) and hook it up on the second floor cable. Will this work? Or does comcast somehow know each and every cable modem in its network? I was poking around the interface of the comcast modem and there is a utilities tab. In this tab is a button that says 'ISP only' Clicking this button brings up a dialog with 'password of the day'. Are these the settings that the cable guy has to set so the modem works? Since I already pay comcast for one modem, shouldnt I be able to add as many modems as I like to the line? I actually want separate wired LANs.

You can not add another modem to your account unless you are willing to pay for an additional account and even then Comcast may not allow it. Instead for less money add a pair of MOCA adapters.

https://www.amazon.com/b?node=17911...&pf_rd_p=facd81cd-745b-46a8-9d19-86492c36ae35

Then replace as necessary any splitters that our in your network that might not be MOCA capable and also add a MOCA filter at the ground block to prevent your data from feeding into Comcast's system and perhaps being visible to your neighbors.
 

sfx2000

Part of the Furniture
Since I already pay comcast for one modem, shouldnt I be able to add as many modems as I like to the line? I actually want separate wired LANs.

Put an Ethernet switch after the Cable Modem, and hook up another router for your other separate LAN. That LAN will be completely separate and no routing between them without setting up some kind of tunnel between them.

Cable ISP's provision the modem, but generally allow up to three attached Ethernet devices behind the modem for residential accounts - and that can be direct attached PC's, or whatever...
 
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