The Good Computer Guy Blog :: Comcast Static IP addresses

Tags: Internet

Comcast business customers with static IP addresses actually get one extra static IP with their account. That is because the static IP address assigned to you gets passed through the Comcast SMC modem/router (which I'll refer to as the "modem" to avoid confusion) to your own networking hardware. But the Comcast modem itself ALSO has its own IP address which you can make use of if everything is set up properly.

The modem has 4 ports. The first port should be connected to your router which will be set up with the proper port forwarding (web, e-mail, ftp, etc.) Your router will have the fixed IP address information hard coded. However any other computer (or another router) plugged into the modem will get a dynamic IP address in another network. If you access the Internet from there you'll see that you're coming from the gateway IP address (usually your IP plus 1.) You can make use of that other address however you want - a second web server, mail server, etc. - by utilizing port forwarding in the Comcast modem.

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Comments

1 - This is very interesting. I used to have Comcast, but then it switched to Time-Warner when they acquired the local business. The modem stayed the same - do you think this will still work?

Posted by Bryan At 11:50:39 PM On 09/17/2008 | - Website - |

2 - Bryan, my guess is "yes" but I'm not positive. Did you have to reconfigure the modem at all when Time Warner took over? What happens when you plug in a computer to one of the other ports on the cable modem? You should get an internal IP address (probably 10.1.10.x.) Then go to What is my IP? on that computer and you'll probably see that your extrernal address is the same as your gateway. If you don't get an IP on the computer then you may need to turn on DHCP on the cable modem (mine was shut off before calling Comcast recently.) Let us know what happens - there are a few other tweaks in there you may need to make.

Posted by Bill Greenberg At 07:12:38 AM On 09/18/2008 | - Website - |