I have read a bunch about fallover setups...but they all seem to assume a business setup where you want full access all the time whether 3G (cellular) or wired...

I only want certain systems to be able to access the 3g setup in case the wired connection fails. I don't want my (literal) multiple gigs of 'cloud' backup or the various windows updates or other silliness to use the cellular network during the fallover.

Some of the 'important' items are wireless...some are wired, some are wired right at the box...some are located in a different room on a wired connection shared with the backup devices etc.

So as it stands, I cannot currently put all the 'important' devices on one port or on a separate router...but if I cannot do it any other way, I am willing to get another router.

Pretty much none of these 'important devices need to be visble directly on the local network...but I do need loopback capability on one device. (So I can access it via the external DNS address, vs the local IP address)

BTW, I have the Hex POE and 3 WAP ACs, and Huawei 3G (LTE) Dongle.

those "important" devices, can they be on static IP? if yes, then you put all of them into one address list,use this list when configure fail-over. Possibility uisng connection mark and then packet park etc. The static route for your fail-over connection only include those marked packet. So that no other devices will get the fail-over connection.

option 2, create a hotspot service on your fail-over connection and using MAC authentication, this way all devices will get to the fail-over WAN interface but only those authenticated by the hotspot get access to the Internet. the benefit of using hotspot, is you can then define how much data each device can use. Or you can just create one account for all important devices (instead of using MAC authentication), then they all share this amount of data. This seems to suite you better.

Thanks, yes I should have mentioned that they are all static ip addresses. I will look at your options!