Welcome to Dave's Tech

This awesome error message is what you will inevitably see if you have UVERSE fiber internet service and a two wire router 3800HGV-B Gateway with a public static ip pool.  The beauty of this device is that it automatically finds and assigns ips to devices based on mac address.  However, problems arise when a device is no longer available on the network and the router still contains ip settings for the device.  There is no option for deleting a device from the router configuration.  If you try to change settings for other existing devices on the network, you may get the error "For the public routed subinterface only WAN IP mapping is allowed".  You may also get an error related to invalid ip settings.  When I called UVERSE tec hnical support, I was instructed to restart the gateway which improved nothing.  I was then told that I would need to do a complete reset of the router which I did not want to do because I had quite a few settings that I did not want to reenter.

The fix for this is not too difficult but took some time to figure out.  Basically, every device that has invalid settings needs to be plugged back into the router so the device can be setup to obtain an ip from the private dhcp assigned sub net.  The problem with this solution is that the devices may not be available to be plugged back in.  In my case, the router retained settings for a laptop that I no longer owned.  The router keeps track of configured devices based on mac address.  The solution then is not to plug in the actual device but rather a device that has the same mac address of the missing device.  I was fortunate enough to have an esxi server with several virtual machines that I could use.  The first thing that needed to be done was to determine all of the mac addresses for the devices that contained invalid settings.  I looked for all of the devices that had an ip setting of "Static IP - No DHCP" and were no longer plugged in to the router. 

First I disabled the Public Routed Subinterface in the router.  I documented the ip settings before disabling.  Using vSphere, I edited a Windows XP vm and assigned the network card to be on a network that is NOT on the network of the router.  I then fired up a Windows XP virtual machine in ESXi and assigned the appropriate mac address to the network card.  I did this in Windows XP software and not the vSphere client because vSphere has a limited range of acceptable mac addresses.  I then shutdown the vm and used vSphere to assign the network card to be on the same network as the router.  I started up the Windows XP vm again.  At this point, for the particular mac address in question, I was able to assign that device to be in the "Private From Pool ..." address assignment and a Wan IP Mapping of "Router Wan IP Address Default".  After doing this for all of the mac address in question,  I enabled the public routed sub interface and was able to make ip configuration changes to devices without getting any errors.

All of this could be accomplished without using ESXi by simpling using a laptop and cycling through all of the mac address in question.