Resetting Your IP With Comcast

The only way you can change your IP address with Comcast is if you use a different modem. IP addresses in Comcast's networks are defined by the MAC addresses of the modem.

(Just as an fyi, you cannot affect your network's connection to the internet with ipconfig commands. They only affect your computer's connection to the home network.)

Jam it back in, in the dark.

You'd have to do some drastic things, like physically changing the hardware, or installing different firmware on the device.

There's nowhere I can't reach.

"Reinstalling" the firmware wouldn't do anything. You would have to have custom firmware specifically hacked to achieve what you want. And on top of that, I believe it may violate Comcast's Terms of Use. (they don't like people altering their modems, and potentially working around bandwidth caps that they have set in place)

Just buy a cheap used modem from someone in your area on craigslist. Its a lot easier.

This thing is sticky, and I don't like it. I don't appreciate it.

Google it
Last bullet point under technical restrictions.

You do not have to have a "specially approved" modem. They all pretty much work the same, so you can use any cable modem under the sun.

I am a dolphin, do you want me on your body?

Odd.
Are you behind a router, or is your computer directly connected to the modem.

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Dude, the most drastic thing k_tak is suggesting is to reboot your computer! Just try it for god's sake.

What kind of toxic man-thing is happening now?

No. I meant that its very simple to answer your own question by doing it yourself. Nothing beats hands-on experimentation, and thats what I was trying to get across.
(I am of course assuming that the "method" you were inquiring about in the previous post was the one k_tak used).

How ya doing, buddy?