Ethernet Through STB Suddenly Started Working, but now it's not

Question

So I've read a lot of posts about this on here and I know it's not supposed to work, but those posts are all about 4/5 years old and for the last few days I've been getting a successful wired connection from the ethernet jack on the back of my STB to my Vizio TV. I recently renovated my living room and when I hooked everything up I plugged in the ethernet cord on a whim and it just randomly started working. It wasn't a fast connection, the connection test on the TV was saying ~4/5 Mbps, but it was fast enough to stream some episodes on Netflix in HD no problem.
My problem is that today it has stopped working again and now that I know it CAN happen I really want to get it working again. Since it worked temporarily, I'm thinking there must have been some DHCP settings that were set just right. I've tried manually adjusting IP settings on the TV and router, but I can't seem to get it working again.  I'm hoping someone here with more specific knowledge can help me
Here's my config:
ONT -> Coax -> Splitter -> Quantum Gateway
                                |
                                 -> Motorola QIP7232 P2 STB -> Ethernet -> Vizio E500I - B1
And before you ask, yes I'm sure that it was working via ethernet and not Wifi. I quadruple checked it, and ever disabled the WiFi just to be sure. So anyone have any thoughts on settings I could mess with?

Answer 1

That's what I thought, especially after having tried it before on my last STB and reading posts saying it wasn't supposed to. I did read some documentation from Motorola on the box itself and it's apparently supported, but there's an asterisk next to it saying something to the affect of "Dependent on software." It specifically states that the box supports DHCP and self assigns it's own IP address and a range of IP addresses that it can assign, I think I just need to figure out what it's assigning to itself so I can use that as Gateway and then try to figure out what range it's assigning dynamnically. Since there's only 1 thing connected it will most likely end up being the first number in that range and rarely increment.  I haven't been able to get it to work again (frankly I haven't put too much effort into it since my TV already has wifi so I don't exactly need this), but I'm going to try recreating the circumstances around when it worked and see if I can copy the settings while it's working. The box had been off and unplugged for several days and seemed to have lost most of it's settings temporarily, so Im betting that had something to do with it.