I have enabled UPnP and Zero Config on my modem. Port mapping and everything worked fine for a while. Then recently it stopped working and we hve not made no chages to the network or modem. I have called Comcast Support twice and they do not seem to even know what features I am referring too. Both times the case has been escalated. No follow up so far though. I use Comcast at two other locations. The UPnP and Zero Config work both work fine at the these two locations with the same configuration and modem setup.