I have a brand new TL-R470T that I purchased.  Long story shot, I need to be able to connect 2 mobile broadband routers to the TP-Link then into my computer.

Both conenctions have unlimited bandwidth but they can periodically reset which is a huge no-go for my small business.  I have yet to see them reset at the same time, but I

am sure it could eventually happen.

Anyway, the two mobile broadband routers are from different manufacturers as well as completely different carries.

Aircard 771s using Sprint LTE

Alcatel HH41NH using AT&T LTE

Now, this is where things get very tricky.  I can easily plug the Aircard into a dedicated Intel NUC that has a fresh install of Windows 10 Pro.  The drivers install and I get shareable internet.  The way I tested it to make sure it shares the Sprint internet is through basic internet sharing and then plugging a cat5e into the ethernet with the other end going to my main desktop(the NUC is not used for remote/streaming work - just a middle man for now).  I am now on the internet on my main desktop as I type this and have a perfectly fine internet connection.  If I input 192.168.0.1 on this machine, I get the TP-Link Load Balancer login page(as expected).  Also, if I input 192.168.1.1 on the NUC, I get the Aircard login page(as expected).  Now, the NUC gets a 192.168 based IP from the LAN that is built into the Aircard but I am also able to clearly see the actual real IP address on the router pages.

For my extensive testing that I have done with my limited knowledge, I swapped the ethernet from gonig to this computer and into WAN port 1 on the R470T.  I put an ethernet cable going from the solo LAN port(the last port on the R470T) to this desktop I am using.

So, it isn't getting the actual IP from Aircard itself but an IP based on the 192.168.x.x given to the NUC through LAN on the Aircard.  If I try a ping attempt to 8.8.8.8, it times out.

That's where I am stuck with the Aircard.  I am obviously getting shareable internet as this desktop would not get internet otherwise when I directly connect the NUC to this desktop.

Moving on to the Alcatel, things look more promising.  The Alcatel has two outbound ethernet connections.  I have plugged in an ethernet cable from port 1 into WAN/LAN 1 on the R470T(that's the first hybrid port - actually the second port if you are looking at the R470T).  Similar outcome.  I can do the same process of connecting the desktop from the Alcatel's ports and get internet that is also shareable(but unnecessary to add yet another machine).  The desktop is given a 192.168 based IP but I can log into the router and see the AT&T IP address easily enough.  If I view the connection status via the R470T(the Alcatel being plugged into WAN/LAN 1 as previously stated):

The interesting change here from the Sprint connection is that I CAN get a successful ping test.  But, I cannot traceroute successfully.  

Here is a simplified layout of topography:

Aircard -> NUC -> WAN R470T

Alcatel -> WAN/LAN 1 R470T

LAN -> this desktop

Not getting any internet on this desktop in that configuration.  I would appreciate ANY possible suggestions on how to go about solving this situation.  I have confidence it can be done somehow.  Years back, I successfully connected a phone in hotspot configuration to a computer which then shared the internet to a wireless router which then fed multiple devices through the LAN ports to 4 computers(was a mess but was necessary for a temporary solution way back in 2014).  I did not really have to work any magic there though.

Just kind of lost here on what I need to do in order to get 2 sources of internet to work on 1 machine and this was the method I wanted to try first without paying some horrible monthly fee to do it through cloud based applications.