Time Capsule Generating it's own IP Address? Installed a new cable modem. Connected my iMac directly to the new modem and, as expected, got a new IP address. However, after I connected my Time Capsule to the modem so I could do everything wirelessly, I notice that my IP address went back to what it had been originally (prior to installing the new modem). As an experiment, I connected iMac directly to the new cable modem and found I had yet another, entirely different IP address.
Is my Time Capsule somehow generating the IP address?
There are settings in the Time Capsule you can modify.

Open up Airport Utility.app, click your Time Capsule, then "Manual Setup". When the management dialog loads, click "Internet" up at the top, then "DHCP" in the category/tab bar.

Ref:https://apple.stackexchange.com/a/23779/46541