How can I get control of my modem back?

@XfinityJamesC​ 

Currently the issue is with Port Forwarding.

In a normal situation where you have a server hosting a service, you would first give that server a static IP address. Then you forward the ports to that static IP address.

I'll leave out the three days it took me to get the stupid interface on the modem to actually assign a static IP address on to the device instead of DHCP, and getting it to assign the IP address I wanted.

In the Xfinity app, you are not able to forward to a static IP address. I figured maybe it was being smart and using the MAC address for routing. But no, that is not the case.

So I have to let the server have a random address assigned by DHCP. Then after a few days when the X-fail app has finally figured out what the actual IP address for the server is, then I can forward the ports.

And that works fine for a few days.

Then, because the server is getting its IP address via DHCP, the IP address on the device changes. And this is where it gets really stupid.  Device has a new IP address. If I look up the device details in the X-fail app it shows the new address for the device. However, in the Port Forwarding section it is still showing the old address.  Shut everything down for a few, turned it back on. No change. App is still an idiot and doesn't know what the changed IP address is.

Called support, and after like half an hour, they said "oh we will set it so that the DHCP is updated, and we will configure it to happen weekly so this doesn't happen anymore." Basically said it would take an hour to fully refresh, and I should see the changes after rebooting the modem.

Well none of that actually happened. X-fail app still shows the old IP address in port forwarding.

Now before yall started forcing us to use two different systems to manage our network, this was never an issue.
And for a long while, I did what was recommended by just bridging the idiot modem to a real modem that I can configure how I need. Unfortunately, someone also decided that the bridge port will not be the high-speed port on my device, so I only get 900Mbps instead of 1400Mbps. I'm a power user, so that is a pretty big drop.

So basically, I need control of my device again, because whoever designed the apps for idiots didn't do it right.

Thank you so much for letting us know the steps you have taken so far @MrJoeHandyman, I apologize the process has not been as easy as intended. [Edited: Information Corrected]:

At this time, our xFi Gateways, including the XB8, require using the Xfinity app to set up port forwarding. We will want to make sure a Static IP for the device is not set up. The Xfinity app will use the IP address from DHCP to set a static MAC bind and establish the port forward rule.

@XfinityBrianH​ Bridge mode is for using a device to manage the network other than the modem. It is not required for port forwarding. I did have the XB8 bridged to an EdgeRouter4 previously, but wanted to take advantage of the faster speeds available on Wifi and via the one high-speed port. Can't do that if you are bridged.

Thank you for your patience @MrJoeHandyman! We apologize for the Information previously provided regarding bridge mode. We made sure to update the message above with the correct information.

@XfinityAldrik​ Unfortunately, that still isn't useful at all.

The App fails at performing the function.   If it worked the way it was "supposed" to, I wouldn't be here trying to fix the modem to work the way it should.