So when I try to add or modify a port forwaring rule in my xfinity wireless gateway (TG1682G) I get the unhelpfull error "Failure! Please check your inputs." . My inputs are fine, and I even get it if i click on edit on a rule, and hit save without changing anything. I have tried on Chrome and Edge browsers. I saw a previous answer on a similar problem from 5 years ago, and it had the unhelpful solution of resetting the gateway to factory settings, but I don't want to do that in the case it doesn't actually help and makes me have to go through the process of adding all the settings again. Any ideas? Is this the latest gateway that Xfinity has available?
Seems like Xfinity is only allowing ports to be forwarded on the DHCP range of the local network. Not sure why, possibly it's a bug, but to get around it. Change your DHCP start/end range to cover the local IP you are trying to forward, then setup your forward and then change the DHCP range again. Hope this helps.