For anyone interested, I did find a way to get my DPC3825 into bridge mode (to be a straight pass-through device, and not act as a router.) Most people will have no need or desire to do this, and if you're not comfortable managing and securing your own network, you should not do any of this. It is very likely customer support will not provide any help in this endeavor, and you may leave your home network vulnerable to attack. With that being said, proceed at your own risk.
First, you have to do a factory reset on the device (use a pen and depress the reset button for 10 seconds...the device will reboot). This will reset the device to CISCO's default firmware. You can find CISCO's manual for the device here: http://www.cisco.com/web/consumer/support/userguides2/4021196_B.pdf
, as it describes the non-Mediacom admin screens of the device. The IP Address will be reset to 192.168.0.1. If you connect directly to the device, you should be able to browse to the IP Address to bring up the admin. If you want to connect wirelessly, the SSID was reset to the last 6 characters of the devices MAC Address, and the PSK is the S/N value of the device. You can find this information on the sticker on the bottom of the physical device.
Second, you need to use the CISCO admin screens to put the device into bridge mode (instead of "Router Mode"). However, the UI to achieve this doesn't actually exist in CISCO's admin screens. But you can still [HTTP] POST the proper data to the device and put it into bridge mode. See http://ohmsblog.teamohms.org/2012/06/how-to-switch-cisco-dpc3825-epc3825.html
for more info.
Essentially, you need to go to the "Administration" screen and the "Management" tab. The <form> element on this page can accept a value for "working_mode". A value of 0 is for router mode, and a value of 1 is for bridge mode. All you have to do is POST this value to this form and the device will accept it. You'll know it worked because you'll get a rebooting... screen after submitting the value.
You can submit/post this value to the form in any number of ways. The simple way I did it was by using the Dev Tools within the Google Chrome browser. Open the dev tools, drill down into the <form> element, edit the HTML and simply add an <input> tag with the proper name and value. Then within the page click the "Save Settings" button. This will submit/post your inserted name/value to the form.
After rebooting to bridge mode, you're on your own as to what you do next. But here's some things to know:
* If you are hard-wired to the DCP3825 (ethernet), your computer is now publicly exposed to the internet. This is dangerous if you are not properly protected.
* The DCP3825 does not automatically turn off the wireless side when in bridge mode. I didn't experiment much here as I simply disabled the wireless after switching to bridge mode.
* The IP Address of the device switches to 192.168.100.1 when in bridge mode (wireless side only). I believe much of the network services (DHCP, etc.) are turned off when router functionality is disabled. If you connect to the device wirelessly, you may need to give yourself a static IP Address in the 192.168.100.0/24 range in order to communicate with it.
One nice [potential] side effect of me doing this is my connection is measurably faster. Before, I consistently tested at 9 Mbps on http://speedtest.net/
. After switching to bridge mode and using my own router, firewall, etc. I regularly test at 27 Mbps. However, there are many variables at play here, and just switching the DCP3825 to bridge mode may not be the reason behind this apparent increase in network speed.